Synthesis of a novel class of fatty acids-derived isoquinolines

Chemistry and Physics of Lipids 135 (2005) 131–145

Synthesis of a novel class of fatty acids-derived isoquinolines Iwona Matuszewska, Andrzej Leniewski, Piotr Roszkowski, Zbigniew Czarnocki ∗ Faculty of Chemistry, Warsaw University, Pasteur St. 1, 02-093 Warsaw, Poland Received 19 October 2004; received in revised form 31 January 2005; accepted 9 February 2005 Available online 16 March 2005

Abstract Two series of novel tetrahydroisoquinoline derivatives bearing at C-1 position a carbon chain derived from fatty acids were prepared employing two complementary synthetic methodologies. The Pictet–Spengler condensation was performed on myristyl, palmityl, stearyl and oleyl aldehydes, whereas the Bischler–Napieralski cyclization used pelargonic, stearic, linolenic and arachidonic acids. The ability to apply both methods allows further labeling of the final 1-substituted-1,2,3,4-tetrahydroisoquinolines for biological studies. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: N-Acyldopamines; Neurotransmitters; Lipids; Fatty acids; Parkinson disease

1. Introduction The derivatives of biologically important amines (e.g. catecholamines) and long-chain fatty acids have gained considerable interest in recent years as a new family of lipids (Boger et al., 1998). Fatty acids of different chain lengths and a different number of double bonds were used to construct suitably designed derivatives to study the carrier-mediated transport of catecholamines (e.g. dopamine) to the brain. Due to the presence of the blood–brain barrier, the central nervous system is prevented from the entry of different xenobiotics. The uptake of the xenobiotic molecules ∗ Corresponding author. Tel.: +48 22 8220211; fax: +48 22 8225996. E-mail address: [email protected] (Z. Czarnocki).

into the brain could be greatly facilitated by linking them to the lipophilic part of a substance that normally is able to pass through blood–brain barrier due to its amphiphilic character (a carrier molecule). Particularly, the amide derivatives of fatty acids (bioactive fatty acid amides) were specified as a new class of lipid bioregulators (Shashoua and Hesse, 1996; Bezuglov et al., 1997). Even simple long-chain amides like Nacylethanolamines (anandamides) exhibit a wide range of biological activity including the role as the endogenous cannabinoids (Hillard et al., 1995). There are some indications that during the metabolism of N-acyldopamines they might be transformed into the isoquinoline systems. The presence of some tetrahydroisoquinoline alkaloids in animal neural tissues was unambiguously demonstrated (Zhu et al., 2002). Also, dopamine-derived naturally occurring

0009-3084/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.chemphyslip.2005.02.008

132

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

endogenous isoquinoline or ␤-carboline alkaloids were examined in connection with parkinsonism (Nagatsu, 2002; Naoi et al., 1996). Bioactive fatty acid amides have been recently suggested to play an important role in the nervous system (Bisogno et al., 1998). Amides of polyunsaturated fatty acids and dopamine were demonstrated to induce cannabinoid-like effects in vivo (Bezuglov et al., 2001). The possibility that neurotransmitters exist in N-acylated forms was postulated by Pokorski and Matysiak already in 1998 (Pokorski and Matysiak, 1998). Pokorski and Czarnocki have recently shown on the basis of radioactive labeling that N-acyldopamines can easily move through the brain–blood barrier and may therefore play role as pro-drugs capable to slowrelease of dopamine within the brain (Pokorski et al., 2003). Also, a long-chain N-acylethanolamines exhibit a wide range of neurochemical activity thus pointing out the role of fatty acid part of the molecule. The endogenous cannabinoids: N-arachidonoylethanolamide (anandamide) and oleoylamide may serve as representative examples. Anandamide has been recently identified as a ligand for cannabinoid receptors. These receptors, whose activation is responsible for a good mood and inhibition of adenoyl cyclase, are found in neuroblastoma cells and in the brain (Hillard et al., 1995). Among other simple fatty acids amides, oleamide (cis9-octadecenoamide) is known as the sleep-inducting factor and suppressor for proliferation of human breast cancer cell. The same kind of anti-cancer activity was postulated for arachidonoylethanolamide (Bisogno et al., 1998). The anti-tumor and anti-inflammatory activity of the endocannabinoidal anandamide and bioactive amides: N-palmitoylethanolamide and oleamide have also been described (De Petrocellis et al., 2000). As it was mentioned above, dopamine derivatives may serve as endogenous isoquinoline precursors in the mammalian brain (Naoi et al., 1996). On the other hand, tetrahydroisoquinolines are very important and interesting group of compounds because of their biological activity, particularly in relation to their endogenous neurotoxicity (Nagatsu, 1997). They are among the most often synthesized natural products (Rozwadowska, 1994; Chrzanowska and Rozwadowska, 2004). In our group we have gained some experience in the synthesis of isoquinolines and ␤-carbolines

(Zi´ołkowski and Czarnocki, 2000; Siwicka et al., 2002). Also recently we have developed an efficient and very mild method for amidation of various longchain fatty acids (Czarnocki et al., 1998). The present paper describes the synthesis of tetrahydroisoquinoline derivatives that contained a fatty acidderived chain that might be regarded as a new class of lipids.

2. Experimental procedures 2.1. Instrumentation Melting points were determined using a Boetius apparatus and were uncorrected. Both 1 H and 13 C NMR spectra were recorded in CDCl3 solutions (unless otherwise stated) on a Varian Unity plus-500 spectrometer (500 and 125 MHz, respectively) with (CH3 )4 Si as the internal standard. Chemical shifts are reported in ppm (δ) and coupling constants (J) in Hz. The symbols: s (singlet), d (doublet), t (triplet), q (quartet), m (multiplet) and br (broadened) are used to describe the multiplicity and shape of signals. Numbering of structures for the presentation of NMR data is shown in Fig. 1. The liquid secondary ion mass spectrometry (LSIMS-positive ion mode) and a high resolution MS spectra were recorded using an AMD-604 spectrometer or Micromass LCT (ESI-TOF) instrument. ESI/MS/MS analyses were carried out in positive and negative modes. Samples were dissolved in THF/MeOH/H2 O (85:10:5, v/v/v) and recorded using an Esquire-LC 1.6g instrument. Dopamine hydrochloride (3-hydroxytyramine hydrochloride) was purchased from Sigma–Aldrich. All reactions were carried out under argon atmosphere. Combining extracts containing products were dried over anhydrous

Fig. 1. Numbering convention for presentation of NMR data in the experimental part.

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

MgSO4 . Solvents were removed on a vacuum rotary evaporator at a maximum temperature of about 35 ◦ C. Chromatographic purification was performed on silica gel MN Kieselgel 60 (70–230 mesh or 100–200 mesh, Merck). Solvents for column chromatography were redistilled. TLC analyses were done on silica gel (Kieselgel 60 F254 , Merck) plates using iodine vapors to visualize the spots. 2.2. General procedure for the preparation of aldehydes (2a–2d) Into a 100-ml round-bottomed flask provided with a magnetic stirrer and under argon atmosphere was placed dry dichloromethane (15 ml). The flask was immersed in dry ice-acetone bath and cooled to −70 ◦ C. A sample of oxalyl chloride (0.6 ml, 7.08 mmol) was then introduced via syringe. To the resulted mixture, a solution of DMSO (1.0 ml) in dichloromethane (15 ml) was slowly introduced dropwise, maintaining the temperature below −50 ◦ C with a continuous stirring. The resulted mixture was again cooled down to −70 ◦ C and stirred for 15 min followed by a very slow addition of the appropriate alcohol (7.0 mmol) in dichloromethane (5 ml). After 15 min of the additional stirring, a solution of triethylamine (4.7 ml) in dichloromethane (10 ml) was added dropwise, maintaining the temperature below −50 ◦ C. The mixture was then stirred at −70 ◦ C for 1 h and it was left stand overnight without an external cooling. The volatile components were then evaporated (caution! evolution of Me2 S), taken up into a fresh portion of dichloromethane (20 ml) and washed successively with solutions of citric acid (5%), saturated sodium bicarbonate and brine. The organic layer was dried, evaporated and the residue was taken immediately to the next step. The analytical samples of aldehydes 2a–2d were prepared by crystallization from hexane. The NMR data were in accordance with those reported in the literature. • Starting from myristyl alcohol (1.50 g) aldehyde 2a (1.40 g, yield 94%) was prepared; m.p. 21–23.5 ◦ C. Literature m.p. 25 ◦ C (Syper and Młochowski, 1984). 1 H NMR (Aurell et al., 1997). • Starting from palmityl alcohol (1.70 g) aldehyde 2b (1.62 g, yield 96%) was prepared. m.p. 35 ◦ C. Literature m.p. 35–36 ◦ C (Kornblum et al., 1982), NMR and IR spectra (Taber et al., 1987).

133

• Starting from stearyl alcohol (1.89 g) aldehyde 2c (1.65 g, yield 88%) was prepared. m.p. 41–43 ◦ C. Literature m.p. 43–44 ◦ C; NMR and IR data (Easton et al., 2001). • Starting from oleyl alcohol (1.88 g) aldehyde 2d (1.70 g, yield 91%) was prepared as a pale yellow oil. Literature NMR and IR data (Tsay et al., 1990). 2.3. General procedure for the preparation of 1-alk(en)yl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinolines (3a–3d) To a suspension of dopamine hydrochloride 1 (0.70 g, 3.7 mmol) in 1-propanol (25 ml), an equimolar amount of aldehyde 2a–2d (myristic, palmitic, stearic or oleic) was added and the mixture was boiled to reflux with stirring under argon atmosphere for 5 h. After cooling to room temperature, the mixture was concentrated under reduced pressure and the residue was chromatographed using chloroform–methanol-aq. ammonia (9:1:0.05, v/v/v) mixture as eluent to give products 3a–3d. 2.3.1. Data for 1-tridecyl-6,7-dihydroxy-1,2,3,4tetrahydroisoquinoline (3a) Starting from myristic aldehyde 2a (0.79 g) the product 3a (0.68 g, yield 52.6%) was obtained as a yellowish amorphous solid following the above procedure. 1 H NMR (DMSO-d6 ) δ 9.07 (br s, 3H-2, two OH, NH), 6.61 and 6.55 (two s, 1H-8, 1H-5), 4.19 (t, 1H-1, J = 6.0 Hz), 3.29 and 3.10 (two m, 2H-3), 2.87 (dt, 1H-4, J1 = 16.5, J2 = 6.5 Hz), 2.73 (dt, 1H-4, J1 = 16.5, J2 = 5.5 Hz), 1.84 (m, 2H-1 ), 1.44 (m, 2H-2 ), 1.18–1.36 (m, 20H, 2H-3 , 2H4 , 2H-5 , 2H-6 , 2H-7 , 2H-8 , 2H-9 , 2H-10 , 2H11 , 2H-12 ), 0.86 (t, 3H-13 , J = 6.8 Hz); 13 C NMR (DMSO-d6 ) δ 144.75, 144.12, 123.54, 122.54, 115.27, 113.17, 53.90, 39.11, 33.55, 31.28, 29.07, 29.02, 28.94, 28.87, 28.71, 24.86, 22.07, 13.89; LSIMS(+) m/z 609, 585, 403, 348 [M + H]+ , 258; HR MS calcd. for C22 H38 NO2 [M + H]+ : 348.2903. Found: 348.2912. 2.3.2. Data for 1-pentadecyl-6,7-dihydroxy-1,2, 3,4-tetrahydroisoquinoline (3b) Starting from palmitic aldehyde 2b (0.79 g) the product 3b (0.83 g, yield 60.0%) was obtained as a colorless oil following the above procedure. 1 H NMR δ

134

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

8.70 (br s, 3H, two OH, NH), 6.63 (s, 2H, H-5, H8), 4.17 (t, 1H-1, J = 6.0 Hz), 3.33 (m, 1H-3), 3.23 (m, 1H-3), 2.89 (m, 1H-4), 2.80 (m, 1H-4), 1.81–1.98 (m, 2H-1 ), 1.48 (m, 2H-2 ), 1.18–1.34 (m, 24H, 2H2 , 2H-3 , 2H-4 , 2H-5 , 2H-6 , 2H-7 , 2H-8 , 2H-9 , 2H-10 , 2H-11 , 2H-12 , 2H-13 , 2H-14 ), 0.88 (t, 3H15 , J = 6.8 Hz); 13 C NMR δ 144.53, 143.84, 123.63, 122.96, 115.76, 113.66, 55.18, 39.74, 34.36, 31.96, 29.85, 29.80, 29.77, 29.76, 29.71, 29.67, 29.49. 29.40, 24.01, 22.71, 14.14; LSIMS(+) m/z 81, 95, 149, 164, 376 [M + H]+ ; HR MS calcd. for C24 H42 NO2 [M + H]+ : 376.3216. Found: 376.3202. 2.3.3. Data for 1-heptadecyl-6,7-dihydroxy1,2,3,4-tetrahydroisoquinoline (3c) Starting from stearic aldehyde 2c (0.99 g) the product 3c (0.79 g, yield 53.1%) was obtained as a yellow oil following the above procedure. 1 H NMR (DMSO-d6 ) δ 9.08 and 8.94 (two br s, 3H, two OH, NH), 6.59 and 6.54(two s, 1H-8, 1H-5), 4.21 (t, 1H-1, J = 6.0 Hz), 3.32 (m, 1H-3), 3.14 (m, 1H-3), 2.84 (dt, 1H-4, J1 = 17.0, J2 = 6.5 Hz), 2.74 (dt, 1H-4, J1 = 17.0, J2 = 5.5 Hz), 1.82 (m, 2H-1 ), 1.42 (m, 2H-2 ), 1.16–1.36 (m, 28H, 2H-3 , 2H-4 , 2H-5 , 2H-6 , 2H-7 , 2H-8 , 2H-9 , 2H-10 , 2H11 , 2H-12 , 2H-13 , 2H-14 , 2H-15 , 2H-16 ), 0.86 (t, 3H-17 , J = 6.8 Hz); 13 C NMR (DMSO-d6 ) δ 144.73, 144.03, 123.40, 122.32, 115.12, 113.06, 53.86, 39.10, 33.42, 31.19, 28.95, 28.90, 28.81, 28.79, 28.60, 24.76, 22.00, 13.86; LSIMS(+): m/z 81, 136, 154, 164, 404 [M + H]+ ; HR MS calcd. for C26 H46 NO2 [M + H]+ : 404.3529. Found: 404.3511. 2.3.4. 1-[(Z)-8-heptadecenyl]-6,7-dihydroxy1,2,3,4-tetrahydroisoquinoline (3d) Starting from oleic aldehyde 2d (0.99 g) the product 3d (0.90 g, yield 60.3%) was obtained as a yellow oil following the above procedure. 1 H NMR δ 6.66 and 6.64 (two s, 2H, H-5, H-8), 5.31 (m, 2H, H-8 , H-9 ), 4.14 (m, 1H-1), 3.20–3.30 (m, 2H-3), 2.80–2.92 (m, 2H-4), 1.98 (m, 4H, 2H-7 , 2H-10 ), 1.10–1.36 (m, 24H, H-1 , H-2 , H-3 , H-4 , H-5 , H-6 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.87 (t, 3H17 , J = 6.8 Hz); 13 C NMR δ 144.37, 143.61, 130.02, 129.64, 123.77, 122.99, 115.72, 113.68, 55.25, 39.40, 34.12, 31.94, 29.85, 29.82, 29.71, 29.59, 29.51, 29.39, 29.34, 27.30, 25.89, 25.63, 22.70, 14.12; LSIMS(+): m/z 81, 137, 164, 178, 402 [M + H]+ .

2.4. General procedure for the preparation of methyl 6,7-bis[(methoxycarbonyl)oxy]-1-alk(en)yl3,4-dihydro-2(1H)-isoquinolinecarboxylates (4a–4d) To a stirred solution of amine 3a–3d (1.50 mmol) in dry dichloromethane (10 ml) a sample of dry pyridine (10 ml) was added. The mixture was cooled to 0 ◦ C in an ice bath. Methyl chloroformate (1.16 ml, 15 mmol) was added dropwise to the solution with stirring. After removal of the cooling bath, the mixture was stirred at room temperature for 10 h. The solvents were then evaporated and water (20 ml) was added to the residue. The mixture was extracted with toluene (2 × 10 ml) and the combined toluene extracts were washed with 1% acetic acid (6 × 5 ml) and sodium hydrogen carbonate solution and dried. The residue, which was obtained after evaporation was purified by column chromatography using chloroform as eluent. Solid products were recrystallized from hexane. 2.4.1. Data for methyl 6,7-bis[(methoxycarbonyl) oxy]-1-tridecyl-3,4-dihydro-2(1H)-isoquinolinecarboxylate (4a) Starting from 3a (0.52 g) the product 4a (0.36 g, yield 46.6%) was obtained as a colorless solid applying the above procedure m.p. 56–57 ◦ C. 1 H NMR (two stable conformers present, ratio ca. 6:5). Major conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 3:1, H-8, H-5), 5.05 (dd, H-1, J1 = 7.4, J2 = 1.8 Hz), 4.25 (dd, H-3, J1 = 13.3, J2 = 4.5 Hz), 3.90 and 3.89 (two broadened s, intensity ratio 3:4, OCOOCH3 ), 3.71 (s, NCOO-CH3 ), 3.18 (m, H-3), 2.93 (m, H-4), 2.70 (m, H-4), 1.78 (m, H-1 ), 1.68 (m, H-1 ), 1.20–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 ), 0.88 (t, H-13 , J = 6.8 Hz); minor conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 3:1, H-8, H-5), 5.17 (dd, H-1, J1 = 5.6, J2 = 2.2 Hz), 4.03 (m, H-3), 3.90 and 3.89 (two broadened s, intensity ratio 3:4, OCOO-CH3 ), 3.72 (s, NCOO-CH3 ), 3.28 (m, H-3), 2.93 (m, H-4), 2.70 (m, H-4), 1.78 (m, H-1 ), 1.68 (m, H-1 ), 1.20–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 ), 0.88 (t, H-13 , J = 6.8 Hz); 13 C NMR δ 156.18, 153.43, 140.53, 140.36, 137.09, 136.93, 133.11, 132.80, 123.19, 122.91, 121.52, 121.22, 55.78, 54.34, 54.29, 52.70, 52.66, 37.46, 36.71, 36.59, 31.94, 29.70, 29.68, 29.66, 29.64, 29.56, 29.37, 28.12, 27.77,

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

26.25, 26.24, 22.70, 14.13; LSIMS(+) m/z 280, 338, 522 [M + H]+ , 1043 [2M + H]+ ; positive electrospray MS m/z 446, 490, 522 [M + H]+ , 544 [M + Na]+ ; HR MS calcd. for C28 H44 NO8 [M + H]+ : 522.3067. Found: 522.3053. 2.4.2. Data for methyl 6,7-bis[(methoxycarbonyl) oxy]-1-pentadecyl-3,4-dihydro-2(1H)-isoquinolinecarboxylate (4b) Starting from 3b (0.56 g) the product 4b (0.51 g, yield 61.3%) was obtained as a colorless solid applying the above procedure 2.4. m.p. 63–65 ◦ C. 1 H NMR (two stable conformers present, ratio ca. 10:9). Major conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 5:3, H-8, H-5), 5.04 (dd, H-1, J1 = 7.8, J2 = 1.8 Hz), 4.25 (dd, H-3, J1 = 12.6, J2 = 4.5 Hz), 3.90 and 3.89 (two broadened s, intensity ratio 3:4, OCOOCH3 ), 3.71 (s, NCOO-CH3 ), 3.17 (m, H-3), 2.92 (m, H-4), 2.71 (m, H-4), 1.78 (m, H-1 ), 1.67 (m, H-1 ), 1.20–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 ), 0.88 (t, H-15 , J = 6.8 Hz); minor conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 5:3, H-8, H-5), 5.17 (dd, H-1, J1 = 6.5, J2 = 1.4 Hz), 4.03 (m, H-3), 3.90 and 3.89 (two broadened s, intensity ratio 3:4, OCOOCH3 ), 3.72 (s, NCOO-CH3 ), 3.27 (m, H-3), 2.92 (m, H-4), 2.71 (m, H-4), 1.78 (m, H-1 ), 1.67 (m, H-1 ), 1.20–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 ), 0.88 (t, H15 , J = 6.8 Hz); 13 C NMR δ 156.17, 153.42, 153.35, 140.50, 140.34, 137.17, 136.92, 133.11, 132.80, 123.19, 122.90, 121.51, 121.22, 55.79, 55.77, 54.38, 54.28, 52.70, 52.67, 37.43, 36.69, 36.57, 31.94, 29.71, 29.68, 29.67, 29.64, 29.56, 29.38, 28.11, 27.76, 26.29, 26.24, 22.71, 14.13; LSIMS(+) m/z 91, 107, 136, 338, 550 [M + H]+ , 572 [M + Na]+ ; positive electrospray MS m/z 474, 518, 550 [M + H]+ , 572 [M + Na]+ ; HR MS calcd. for C30 H48 NO8 [M + H]+ : 550.3380. Found: 550.3355. 2.4.3. Data for methyl 6,7-bis[(methoxycarbonyl) oxy]-1-heptadecyl-3,4-dihydro-2(1H)-isoquinolinecarboxylate (4c) Starting from 3c (0.60 g) the product 4c (0.49 g, yield 56.6%) was obtained as a colorless solid applying the procedure 2.4. m.p. 68–70 ◦ C. 1 H NMR (two stable conformers present, ratio ca. 6:5). Major conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 5:2,

135

H-8, H-5), 5.04 (dd, H-1, J1 = 10.0, J2 = 3.3 Hz), 4.26 (dd, H-3, J1 = 12.6, J2 = 4.5 Hz), 3.90 and 3.89 (two broadened s, intensity ratio 2:3, OCOO-CH3 ), 3.71 (s, NCOO-CH3 ), 3.18 (m, H-3), 2.92 (m, H-4), 2.70 (m, H-4), 1.79 (m, H-1 ), 1.66 (m, H-1 ), 1.22–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H17 , J = 6.8 Hz); minor conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 5:2, H-8, H-5), 5.18 (dd, H-1, J1 = 8.8, J2 = 3.8 Hz), 4.03 (m, H-3), 3.90 and 3.89 (two broadened s, intensity ratio 2:3, OCOOCH3 ), 3.72 (s, NCOO-CH3 ), 3.27 (m, H-3), 2.92 (m, H-4), 2.70 (m, H-4), 1.79 (m, H-1 ), 1.66 (m, H-1 ), 1.22–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 , H-15 , H16 ), 0.88 (t, H-17 , J = 6.8 Hz); 13 C NMR δ 156.17, 153.42, 140.50, 140.33, 137.20, 136.94, 133.09, 132.81, 123.17, 122.93, 121.52, 121.24, 55.78, 54.32, 52.69, 37.42, 36.68, 31.94, 29.72, 29.70, 29.57, 29.38, 28.09, 27.78, 26.27, 22.71, 14.14; LSIMS(+): m/z 107, 154, 338, 522, 578 [M + H]+ , 1155 [2M + H]+ ; HR MS calcd. for C32 H52 NO8 [M + H]+ : 578.3693. Found: 578.3672.

2.4.4. Data for methyl 6,7-bis[(methoxycarbonyl) oxy]-1-[(Z)-8-heptadecenyl]-3,4-dihydro-2(1H)isoquinolinecarboxylate (4d) Starting from 3d (0.60 g) the product 4d (0.64 g, yield 74.2%) was obtained as a yellow oil applying the above procedure. 1 H NMR (two stable conformers present, ratio ca. 10:9). Major conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 3:1, H-8, H-5), 5.35 (m, H-8 , H-9 ), 5.04 (dd, H1, J1 = 10.0, J2 = 3.9 Hz), 4.25 (dd, H-3, J1 = 13.2, J2 = 4.5 Hz), 3.90 and 3.89 (two broadened s, intensity ratio 2:3, OCOO-CH3 ), 3.71 (s, NCOO-CH3 ), 3.17 (m, H-3), 2.91 (m, H-4), 2.70 (m, H-4), 2.01 (m, H7 , H-10 ), 1.79 (m, H-1 ), 1.65 (m, H-1 ), 1.22–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-11 , H-12 , H13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); minor conformer: δ 7.02 and 7.00 (two broadened s, intensity ratio ca. 3:1, H-8, H-5), 5.35 (m, H-8 , H-9 ), 5.17 (dd, H-1, J1 = 8.8, J2 = 4.2 Hz), 4.02 (m, H-3), 3.90 and 3.89 (two broadened s, intensity ratio 2:3, OCOO-CH3 ), 3.72 (s, NCOO-CH3 ), 3.27 (m, H-3), 2.91 (m, H-4), 2.70 (m, H-4), 1.79 (m, H-1 ), 2.01 (m, H-7 , H-10 ), 1.79 (m, H-1 ), 1.65 (m, H-

136

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

1 ), 1.22–1.44 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H17 , J = 6.8 Hz); 13 C NMR δ 156.17, 153.42, 153.34, 140.50, 140.33, 137.15, 136.90, 133.10, 132.80, 129.99, 129.94, 129.85, 129.78, 129.04, 128.23, 125.30, 123.19, 122.92, 121.51, 121.21, 55.79, 55.78, 54.33, 54.26, 52.71, 52.67, 37.42, 36.68, 36.55, 31.91, 29.78, 29.76, 29.53, 29.46, 29.33, 29.29, 28.10, 27.74, 27.23, 26.28, 26.22, 22.70, 14.13; LSIMS(+) m/z 95, 109, 280, 338, 576 [M + H]+ ; positive electrospray MS m/z 500, 544, 576 [M + H]+ , 598 [M + Na]+ ; HR MS calcd. for C32 H50 NO8 [M + H]+ : 576.3536. Found: 576.3508. 2.5. General procedure for the preparation of methyl 1-alk(en)yl-6,7-dihydroxy-3,4-dihydro2(1H)-isoquinolinecarboxylates (5a–5d) A solution of isoquinolinecarboxylate 4a–4d (0.80 mmol) in dry methanol (25 ml), containing 1 ml of 25% aqueous solution of ammonia, was allowed to stand overnight at 5 ◦ C. The reaction mixture was then evaporated in vacuo to dryness and the residue was chromatographed using chloroform and chloroform–methanol mixture (96:4, v/v) to give colorless solids. The crude products were subsequently recrystallized from hexane-cyclohexane to collect 5a–5d. 2.5.1. Data for methyl 1-tridecyl-6,7-dihydroxy3,4-dihydro-2(1H)-isoquinolinecarboxylate (5a) Starting from 4a (0.42 g) the product 5a (0.20 g, yield 62.8%) was obtained applying the above procedure m.p. 124–125 ◦ C; 1 H NMR (two stable conformers present ratio ca. 2:1). Major conformer: δ 7.57 and 5.88 (two br s, two OH), 6.63 and 6.61 (two s, H-8, H-5), 5.00 (dd, H-1, J1 = 9.2, J2 = 5.3 Hz), 3.94 (dt, H-3, J1 = 13.7, J2 = 4.4 Hz), 3.76 (s, NCOOCH3 ), 3.32 (m, H-3), 2.77 (m, H-4), 2.62 (dt, H-4, J1 = 15.8, J2 = 3.8 Hz), 1.72 (m, H-1 ), 1.63 (m, H1 ), 1.18–1.36 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H7 , H-8 , H-9 , H-10 , H-11 , H-12 ), 0.88 (t, H-13 , J = 6.8 Hz); minor conformer: δ 6.52 and 6.03 (two br s, two OH), 6.59 and 6.56 (two br s, H-8, H-5), 4.89 (dd, H-1, J1 = 9.0, J2 = 4.0 Hz), 4.10 (m, H-3), 3.73 (s, NCOO-CH3 ), 3.20 (m, H-3), 2.77 (m, H-4), 2.54 (dt, H-4, J1 = 5.5 Hz), 1.72 (m, H-1 ), 1.63 (m, H-1 ),

1.18–1.36 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 ), 0.88 (t, H-13 , J = 6.8 Hz); 13 C NMR major conformer δ 156.89, 143.30, 142.29, 129.40, 125.35, 114.76, 113.63, 55.08, 53.08, 38.40, 36.74, 31.94, 29.72, 29.69, 29.68, 29.64, 29.59, 29.38, 27.64, 26.34, 22.70, 14.13; minor conformer δ 156.89, 143.30, 142.53, 129.98, 125.83, 115.28, 113.48, 54.59, 52.86, 37.80, 36.88, 31.94, 29.72, 29.69, 29.68, 29.64, 29.59, 29.38, 27.43, 26.31, 22.70, 14.13; LSIMS(+): m/z 137, 154, 222, 406 [M + H]+ , 811 [2M + H]+ ; positive electrospray MS m/z 331, 374, 406 [M + H]+ , 428 [M + Na]+ , 811 [2M + H]+ , 833 [2M + Na]+ ; negative electrospray MS m/z 329, 372, 404 [M-H]- .

2.5.2. Data for methyl 1-pentadecyl-6, 7-dihydroxy-3,4-dihydro-2(1H)-isoquinolinecarboxylate (5b) Starting from 4b (0.44 g) the product 5b (0.21 g, yield 61.7%) was obtained applying the above procedure. m.p. 127–128 ◦ C; 1 H NMR (two stable conformers present, ratio ca. 7:3). Major conformer: δ 7.46 and 5.66 (two br s, two OH), 6.63 and 6.61 (two s, H-8, H-5), 5.00 (dd, H-1, J1 = 9.4, J2 = 4.5 Hz), 3.94 (m, H-3), 3.77 (s, NCOO-CH3 ), 3.33 (m, H-3), 2.78 (m, H-4), 2.63 (dt, H-4, J1 = 15.8, J2 = 3.8 Hz), 1.72 (m, H1 ), 1.63 (m, H-1 ), 1.16–1.40 (m, H-2 , H-3 , H-4 , H5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 ), 0.88 (t, H-15 , J = 6.8 Hz); minor conformer: δ 6.06 and 5.69 (two br s, two OH), 6.59 and 6.58 (two s, H-8, H-5), 4.91 (dd, H-1, J1 = 9.0, J2 = 4.7 Hz), 4.12 (m, H-3), 3.72 (s, NCOO-CH3 ), 3.20 (m, H-3), 2.78 (m, H-4), 2.54 (dt, H-4, J1 = 15.4, J2 = 4.0 Hz), 1.72 (m, H-1 ), 1.63 (m, H-1 ), 1.16–1.40 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H11 , H-12 , H-13 , H-14 ), 0.88 (t, H-15 , J = 6.8 Hz); 13 C NMR: major conformer δ 156.85, 143.42, 142.24, 129.45, 125.42, 114.74, 113.62, 55.06, 53.05, 38.39, 36.75, 31.94, 29.73, 29.69, 29.68, 29.64, 29.59, 29.38, 27.65, 26.34, 22.71, 14.13; minor conformer δ 156.74, 143.42, 142.35, 130.20, 126.03, 115.33, 113.53, 54.51, 52.79, 37.72, 36.89, 31.94, 29.73, 29.69, 29.68, 29.64, 29.59, 29.38, 27.42, 26.29, 22.71, 14.13; LSIMS(+) m/z 222, 434 [M + H]+ , 867 [2M + H]+ ; negative electrospray MS m/z 357, 400, 432 [M − H]; HR MS calcd. for C26 H44 NO4 [M + H]+ : 434.3270. Found: 434.3258.

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

2.5.3. Data for methyl 1-heptadecyl-6, 7-dihydroxy-3,4-dihydro-2(1H)-isoquinolinecarboxylate (5c) Staring from 4c (0.46 g) the product 5c (0.26 g, yield 69.5%) was obtained applying the above procedure. m.p. 116–119 ◦ C; 1 H NMR (two stable conformers present ratio ca. 2:1). Major conformer: δ 7.33 and 5.63 (two br s, two OH), 6.63 and 6.61 (two s, H-8, H-5), 5.01 (dd, H-1, J1 = 9.7, J2 = 5.5 Hz), 3.93 (m, H-3), 3.76 (s, NCOO-CH3 ), 3.32 (m, H3), 2.79 (m, H-4), 2.03 (m, H-4), 1.57–1.80 (m, H-1 ), 1.16–1.40 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 , H14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); minor conformer: δ 6.59 (s, H-5 and H-8), 5.94 and 5.63 (two br s, two OH), 4.91 (dd, H-1, J1 = 9.0, J2 = 4.7 Hz), 4.12 (dt, H-3, J1 = 10.8, J2 = 2.7 Hz), 3.72 (s, NCOO-CH3 ), 3.20 (m, H-3), 2.79 (m, H-4), 2.55 (dt, H-4, J1 = 15.4, J2 = 1.8 Hz), 1.57–1.80 (m, H1 ), 1.16–1.40 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); 13 C NMR major conformer δ 156.80, 142.21, 129.54, 125.47, 114.75, 113.69, 55.02, 53.00, 38.37, 36.76, 31.94, 29.73, 29.60, 29.38, 27.67, 26.32, 22.70, 14.13; minor conformer δ 156.80, 143.34, 130.30, 126.26, 115.34, 113.63, 54.52, 52.72, 37.65, 36.76, 31.94, 29.73, 29.60, 29.38, 27.36, 26.32, 22.70, 14.13; LSIMS(+): m/z 107, 222, 462 [M + H]+ , 923 [2M + H]+ ; negative electrospray MS m/z 385, 428, 460 [M-H]− , positive electrospray MS m/z 460, 462 [M + H]+ , 484 [M + Na]+ . 2.5.4. Data for methyl 1-[(Z)-8-heptadecenyl]-6, 7-dihydroxy-3,4-dihydro-2(1H)-isoquinolinecarboxylate (5d) Starting from 4d (0.46 g) the product 5d (0.26 g, yield 71.0%) was obtained applying the above procedure. m.p. 96–99 ◦ C; 1 H NMR (two stable conformers present, ratio ca. 2:1). Major conformer: δ 7.42 and 5.81 (two br s, two OH), 6.62 and 6.61 (two s, H8, H-5), 5.33 (m, H-8 , H-9 ), 5.00 (dd, H-1, J1 = 8.2, J2 = 5.2 Hz), 3.93 (m, H-3), 3.76 (s, NCOO-CH3 ), 3.32 (m, H-3), 2.78 (m, H-4), 2.62 (m, H-4), 2.00 (m, H7 , H-10 ), 1.72 (m, H-1 ), 1.63 (m, H-1 ), 1.18–1.42 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-11 , H-12 , H13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); minor conformer: δ 6.59 and 6.58 (two s, H-8, H-

137

5), 6.36 and 5.90 (two br s, two OH), 5.33 (m, H8 , H-9 ), 4.90 (dd, H-1, J1 = 9.3 J2 = 2.2 Hz), 4.10 (m, H-3), 3.73 (s, NCOO-CH3 ), 3.21 (m, H-3), 2.78 (m, H-4), 2.54 (m, H-4), 2.00 (m, H-7 , H-10 ), 1.72 (m, H-1 ), 1.63 (m, H-1 ), 1.18–1.42 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); 13 C NMR major conformer δ 156.88, 143.43, 142.33, 130.01,129.84, 129.46, 129.45, 125.40, 114.80, 113.65, 55.06, 53.04, 38.43, 36.75, 31.92, 29.78, 29.59, 29.54, 29.48, 29.34, 29.33, 27.67, 27.24, 27.22, 26.30, 22.69, 14.11; minor conformer δ 156.88, 142.50, 130.01,129.84, 129.46, 129.45, 125.84, 115.31, 113.52, 54.60, 5.82, 37.85, 36.91, 31.92, 29.78, 29.59, 29.54, 29.48, 29.34, 29.33, 27.43, 27.24, 27.22, 26.30, 22.69, 14.11; LSIMS(+) m/z 107, 137, 472, 482 [M + Na]+ , 504 [M + H+2Na]+ ; negative electrospray MS m/z 458 [M-H]- ; positive electrospray MS m/z 460 [M + H]+ , 482 [M + Na]+ ; HR MS calcd. for C28 H46 NO4 [M + H]+ : 460.3427. Found: 460.3406. 2.6. General procedure for the preparation of methyl 1-alk(en)yl-6,7-dimethoxy-3,4-dihydro2(1H)-isoquinolinecarboxylates (6a–6d) Substrates 5a–5d were dried overnight in a vacuum dessicator over phosphorous pentoxide before the reaction. To a stirred solution of compound 5a–5d (0.50 mmol) in dry acetone (50 ml), containing anhydrous potassium carbonate (1.0 g), a sample of iodomethane (3.0 ml) was added in two portions during 1 h under reflux. After 4 h the mixture was cooled, filtered and the filtrate was concentrated in vacuo. The residue was subjected to column chromatography on silica gel. Elution with chloroform gave products as yellow oils, crystallizing on standing. The crude products were recrystallized from hexane giving pure compounds 6a–c as colorless solids. 2.6.1. Data for methyl 1-tridecyl-6,7-dimethoxy3,4-dihydro-2(1H)-isoquinolinecarboxylate (6a) Starting from 5a (0.20 g) the product 6a (0.15 g, yield 68.0%) was obtained applying the above procedure. m.p. 99–101 ◦ C; 1 H NMR (two stable conformers present, ratio ca. 1:1) δ 6.66, 6.64, 6.56 and 6.53 (four s, H-5, H-8), 5.07 and 4.95 (two dd,

138

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

H-1, J1 = 9.2, J2 = 4.9 and J1 = 9.7, J2 = 3.7 Hz, respectively), 4.18, 3.95, 3.29 and 3.20 (four m, H3), 3.86 (s, two CH3 ), 3.72 (s, CH3 ), 2.74–2.94 and 2.61 (two m, H-4), 1.77 and 1.67 (two m, H-1 ), 1.20–1.44 (m, H-2 , H-3 , H-4 , H-5 , H6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 ), 0.88 (t, H-13 , J = 6.8 Hz); 13 C NMR δ 156.35, 144.95, 144.15, 144.06, 129.77, 129.43, 126.79, 126.51, 114.46, 114.20, 109.43, 109.07, 56.06, 54.67, 54.48, 52.59, 52.52, 38.08, 37.38, 37.08, 36.90, 31.93, 29.70, 29.68, 29.66, 29.62, 29.50, 29.37, 27.84, 27.53, 26.41, 26.32, 22.70, 14.14; LSIMS(+) m/z 151, 236, 250, 434 [M + H]+ , 456 [M + Na]+ ; positive electrospray MS m/z 151, 163, 359, 420; negative electrospray MS m/z 386, 403, 418; HR MS calcd. for C26 H43 NNaO4 [M + Na]+ : 456.3090. Found: 456.3080. 2.6.2. Data for methyl 1-pentadecyl-6,7-dimethoxy-3,4-dihydro-2(1H)-isoquinoline carboxylate (6b) Starting from 5b (0.22 g) the product 6b (0.18 g, yield 76.3%) was obtained applying the above procedure. m.p. 62–63 ◦ C; 1 H NMR (two stable conformers present, ratio ca. 1:1) δ 6.59, 6.58 and 6.55 (three s, H-5, H-8), 5.10 and 4.97 (two dd, H-1, J1 = 9.0, J2 = 5.0 and J1 = 9.5, J2 = 3.7 Hz, respectively), 4.24, 4.00, 3.29 and 3.20 (four m, H-3), 3.86 and 3.84 (two s, CH3 ), 3.72 (br s, CH3 ), 2.87 (m, H-4), 2.62 (dt, H-4, J1 = 15.9, J2 = 3.2 Hz), 1.62–1.84 (m, H-1 ), 1.20–1.40 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 ), 0.88 (t, H-15 , J = 6.8 Hz); 13 C NMR δ 156.31, 147.34, 130.32, 129.95, 126.00, 125.67, 111.56, 111.37, 110.14, 109.84, 56.03, 56.01, 55.89, 55.88, 54.52, 54.39, 52.55, 37.95, 37.28, 36.89, 36.74, 31.94, 29.71, 29.68, 29.67, 29.62, 29.50, 29.37, 28.09, 27.77, 26.41, 26.34, 22.70, 14.13; LSIMS(+) m/z 250, 462 [M + H]+ , 923 [2M + H]+ ; positive electrospray m/z 165, 208, 387, 430, 462 [M + H]+ , 484 [M + Na]+ ; HR MS calcd. for C28 H47 NNaO4 [M + Na]+ : 484.3403. Found: 484.3427. 2.6.3. Data for methyl 1-heptadecyl-6,7-dimethoxy-3,4-dihydro-2(1H)-isoquinoline carboxylate (6c) Staring from 5c (0.23 g) the product 6c (0.20 g, yield 81.7%) was obtained applying the above pro-

cedure. m.p. 58–60 ◦ C; 1 H NMR (two stable conformers present, ratio ca. 1:1) δ 6.59, 6.57 and 6.55 (three s, intensity ratio 2:1:1, H-5, H-8), 5.10 and 4.97 (two dd, H-1, J1 = 9.3, J2 = 5.0 and J1 = 9.9, J2 = 3.9 Hz, respectively), 4.23, 4.01, 3.29 and 3.20 (dd and three m, H-3), 3.86 and 3.85 (two s, two CH3 ), 3.72 (br s, CH3 ), 2.87 and 2.62 (two m, H-4), 1.77 and 1.68 (two m, H-1 ), 1.20–1.42 (m, H-2 , H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H10 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); 13 C NMR δ 156.32, 147.33, 130.32, 129.94, 126.00, 125.66, 111.55, 111.36, 110.13, 109.82, 56.02, 55.89, 54.54, 54.38, 52.53, 52.51, 37.95, 37.27, 36.89, 36.73, 31.94, 29.72, 29.69, 29.67, 29.63, 29.50, 29.37, 28.08, 27.77, 26.41, 26.34, 22.70, 14.14; LSIMS(+) m/z 81, 95, 250, 490 [M + H]+ ; positive electrospray MS m/z 165, 208, 458, 490 [M + H]+ , 512 [M + Na]+ ; HR MS calcd. for C30 H51 NNaO4 [M + Na]+ : 512.3716. Found: 512.3700. 2.6.4. Data for methyl 1-[(Z)-8-heptadecenyl]-6, 7-dimethoxy-3,4-dihydro-2(1H)-isoquinolinecarboxylate (6d) Starting from 5d (0.23 g) the product 6d (0.19 g, yield 78.5%) was obtained as a colorless oil applying the above procedure. 1 H NMR (two stable conformers present, ratio 11:10) δ 6.59, 6.57 and 6.55 (three s, intensity ratio 2:1:1, H-5, H-8), 5.34 (m, H-8 , H9 ), 5.10 and 4.97 (two dd, H-1, J1 = 10.2, J2 = 3.5 and J1 = 8.9, J2 = 4.6 Hz, respectively), 4.23 (dd, H-3, J1 = 13.3, J2 = 4.2 Hz), 4.01, 3.28 and 3.20 (three m, H3), 3.86 and 3.85 (two s, two CH3 ), 3.72 and 3.71 (two s, CH3 ), 2.79–2.95 and 2.59–2.66 (two m, H-4), 2.01 (m, H-7 , H-10 ), 1.64–1.82 (m, H-1 ), 1.22–1.46 (m, H2 , H-3 , H-4 , H-5 , H-6 , H-11 , H-12 , H-13 , H-14 , H-15 , H-16 ), 0.88 (t, H-17 , J = 6.8 Hz); 13 C NMR δ 156.31, 147.65, 147.53, 147.33, 130.29, 129.99, 129.93, 129.86, 129.78, 125.99, 125.65, 111.54, 111.35, 110.11, 109.80, 56.01, 55.88, 54.52, 54.37, 52.59, 52.53, 37.93, 37.27, 36.89, 36.73, 31.91, 29.77, 29.60, 29.53, 29.47, 29.33, 29.31, 29.27, 28.08, 27.76, 27.23, 27.21, 26.40, 26.33, 22.69, 14.13; LSIMS(+) m/z 165, 250, 488 [M + H]+ , 510 [M + Na]+ , 975 [2M + H]+ ; positive electrospray MS m/z 165, 208, 413, 428, 488 [M + H]+ , 510 [M + Na]+ , 997 [2M + Na]+ ; HR MS calcd. for C30 H49 NNaO4 [M + Na]+ : 510.3559. Found: 510.3554.

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

2.7. General procedure for the preparation of N-[2-(3,4-dimethoxyphenyl)ethyl]amides (9e–9g) and (9c) To a stirred mixture of homoveratrylamine 7 (1.09 g, 6.00 mmol) in dry THF (50 ml) BOP (2.65 g, 6.00 mmol) and an equimolar amount of acid 8e–8g or 8c (pelargonic, stearic, linolenic or arachidonic) were added. The mixture was then stirred at room temperature for 10 min, cooled to 5 ◦ C and a solution of triethylamine (2.5 ml) in THF (10 ml) was added dropwise. The cooling bath was then removed and the solution was stirred at room temperature for 12 h. The volatiles were then evaporated and brine (20 ml) and diethyl ether (150 ml) were added to the residue. The aqueous layer was extracted with ether and the combined extracts were washed with saturated sodium hydrogen carbonate solution, dried and evaporated to dryness. The residue was subjected to column chromatography using chloroform–methanol (98:2, v/v) mixture as eluent. The solid products were recrystallized from diethyl ether-hexane to give pure compounds 9e–9g or 9c, respectively with yields 84–88%. 2.7.1. Data for N-[2-(3,4-dimethoxyphenyl)ethyl]nonanamide (9e) Starting from pelargonic acid 8e (0.95 g) the product 9e (1.62 g, yield 84.0%) was prepared following the procedure 2.7. m.p. 73–75 ◦ C; 1 H NMR δ 6.81 (dAB , J1 = 7.8 Hz, 1H-5 ), 6.73 (ddAB , J1 = 7.8, J2 = 1.7 Hz, 1H-6 ), 6.72 (br s, 1H-2 ), 5.43 (br s, NH), 3.87 and 3.88 (two s, 6H-OCH3 ), 3.50 (q, J = 6.8 Hz, 2H-1 ), 2.76 (t, J = 6.8 Hz, 2H-2 ), 2.12 (t, J = 7.6 Hz, 2H-2), 1.60 (m, 2H-3), 1.20–1.35 (m, 10H, H-4, H-5, H-6, H7, H-8), 0.88 (t, J = 6.8 Hz, 3H-9); 13 C NMR δ 173.16, 149.04, 147.68, 131.47, 120.64, 111.88, 111.32, 55.91, 55.87, 40.62, 36.89, 35.33, 31.83, 29.33, 29.31, 29.16, 25.80, 22.65, 14.10; positive electrospray MS m/z 665 [2M + Na]+ , 360 [M+K]+ , 322 [M + H]+ ; HR MS calcd. for C38 H62 N2 NaO6 [2M + Na]+ : 665.4506. Found: 665.4522. 2.7.2. Data for N-[2-(3,4-dimethoxyphenyl)ethyl]octadecanamide (9c) Starting from stearic acid 8c (1.71 g) the product 9c (2.27 g, yield 84.9%) was prepared following the procedure 2.7. m.p. 93–95 ◦ C; 1 H NMR δ 6.81 (dAB , J1 = 8.0 Hz, 1H-5 ), 6.73 (ddAB , J1 = 8.0,

139

J2 = 1.9 Hz, 1H-6 ), 6.72 (br s, 1H-2 ), 5.66 (br s, NH), 3.87 and 3.86 (two s, 6H-OCH3 ), 3.50 (q, J = 6.8 Hz, 2H-1 ), 2.77 (t, J = 6.8 Hz, 2H-2 ), 2.14 (t, J = 7.7 Hz, 2H-2), 1.59 (quintet, J = 7.5, 2H-3), 1.20–1.32 (m, 28H, H-4, H-5, H-6, H-7, H-8, H9, H-10, H-11, H-12, H-13, H-14, H-15, H-16, H17), 0.88 (t, J = 6.9 Hz, 3H-18); 13 C NMR δ 173.43, 149.02, 147.67, 131.35, 120.63, 111.83, 111.27, 55.90, 55.85, 40.73, 36.76, 35.26, 31.94, 29.72, 29.70, 29.68, 29.65, 29.52, 29.38, 29.31, 25.85, 22.71, 14.15; positive electrospray MS m/z 470 [M + Na]+ ; HR MS calcd. for C28 H49 NNaO3 [M + Na]+ : 470.3610. Found: 470.3605. 2.7.3. Data for (9Z,12Z,15Z)-N-[2-(3,4-dimethoxyphenyl)ethyl]octadeca-9,12,15-trienamide (9f) Starting from linolenic acid 8f (1.67 g) the product 9f (2.25 g, yield 85.0%) as a yellow oil was obtained following the procedure 2.7. 1 H NMR δ 6.81 (dAB , J = 7.7 Hz, 1H-5 ), 6.73 (ddAB , J1 = 7.7, J2 = 1.6 Hz, 1H-6 ), 6.72 (br s, 1H-2 ), 5.48 (br t, NH), 5.28–5.43 (m, 6H, H-9, H-10, H-12, H-13, H-15, H-16), 3.87 and 3.86 (two s, 6H-OCH3 ), 3.50 (q, J = 6.7 Hz, 2H1 ), 2.71–2.83 (m, 6H, 2H-11, 2H-14, 2H-2 ), 2.12 (t, J = 7.7 Hz, 2H-2), 2.05 (m, 4H, 2H-8, 2H-17), 1.59 (apparent quintet, 2H-3), 1.23–1.38 (m, 8H, 2H4, 2H-5, 2H-6, 2H-7), 0.97 (t, J = 6.9 Hz, 3H-18)); 13 C NMR δ 173.10, 149.04, 147.68, 131.97, 131.43, 130.25, 128.30, 128.24, 127.74, 127.10, 120.63, 111.87, 111.31, 55.91, 55.87, 40.62, 36.86, 35.32, 29.60, 29.27, 29.13, 27.20, 25.77, 25.62, 25.53, 20.55, 14.29; positive electrospray MS m/z 905 [2M + Na]+ , 883 [2M + H]+ , 480 [M+K]+ , 464 [M + Na]+ , 442 [M + H]+ . 2.7.4. Data for (5Z,8Z,11Z,14Z)-N-[2-(3,4-dimethoxyphenyl)ethyl]icosa-5,8,11,14-tetraenamide (9g) Starting from arachidonic acid 8g (1.83 g) the product 9g (2.47 g, yield 88.0%) as an oil was obtained following the procedure 2.7. m.p. <20 ◦ C. 1 H NMR δ 6.81 (dAB , J = 7.7 Hz, 1H-5 ), 6.72–6.75 (m, 2H, H-6 , H-2 ), 5.29–5.46 (m, 9H, H-5, H-6, H8, H-9, H-11, H-12, H-14, H-15, NH), 3.87 and 3.86 (two s, 6H-OCH3 ), 3.50 (q, J = 6.7 Hz, 2H1 ), 2.74–2.86 (m, 8H, H-2 , H-7, H-10, H-13), 2.02–2.18 (m, 6H, H-2, H-4, H-16), 1.69 (quin-

140

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

tet, J = 7.6 Hz, 2H-3), 1.22–1.40 (m, 6H, H-17, H18, H-19), 0.89 (t, J = 6.8 Hz, 3H-20); 13 C NMR δ 172.77, 149.07, 147.71, 131.38, 130.54, 129.11, 128.76, 128.62, 128.25, 128.16, 127.85, 127.52, 120.62, 111.86, 111.33, 55.93, 55.87, 40.65, 36.17, 35.33, 31.52, 29.33, 27.23, 26.68, 25.64, 25.55, 22.58, 14.09; positive electrospray MS m/z 934 [2M + H]+ , 490 [M + Na]+ , 468 [M + H]+ ; HR MS calcd. for C30 H45 NNaO3 [M + Na]+ : 490.3297. Found: 490.3307. 2.8. General procedure for the preparation of 1alk(en)yl-6,7-dimethoxy-3,4-dihydroisoquinolines (10e–10g) and (10c) Phosphorus pentachloride (0.41 g, 3.0 mmol) was added to the cooled to 0 ◦ C dry dichloromethane (20 ml), containing amide 9e–9g or 9c (2.0 mmol). The solution was stirred for 20 min and then the cooling bath was removed. The mixture was stirred at room temperature under argon atmosphere for 6 h and subsequently was added to a solution of 1.50 g (18.0 mmol) of sodium hydrogen carbonate in water (20 ml). This mixture was stirred for 5 min and then the layers were separated. The aqueous layer was extracted twice with 20-ml portions of dichloromethane. The combined organic extracts were washed with brine (30 ml) and dried. The residue, which was obtained after evaporation, was then purified by column chromatography using 3% (v/v) methanol in chloroform as eluent. The imines thus obtained were quite unstable and should be taken immediately to the next step. 2.8.1. Data for 1-octyl-6,7-dimethoxy-3, 4-dihydroisoquinoline (10e) Starting from amide 9e (0.64 g) the product 10e (0.41 g, yield 67.8%) was isolated as a yellow oil following the procedure 2.8. 1 H NMR δ 7.03 (s, 1H-8), 6.72 (s, 1H-5), 3.94 (s, 3H-OCH3 ), 3.91 (s, 3H-OCH3 ), 3.69 (t, J = 7.7 Hz, 2H-4), 2.79 (t, J = 7.7 Hz, 2H-3 or 2H-1 ), 2.68 (t, J = 7.7 Hz, 2H-3 or 2H-1 ), 1.60–1.70 (m, 2H-2 ), 1.20–1.42 (m, 10H, H-3 , H-4 , H-5 , H-6 , H-7 ), 0.88 (t, J = 7.0 Hz, 3H-8 ); 13 C NMR δ 169.64, 151.91, 147.70, 132.14, 120.84, 110.50, 109.50, 56.29, 56.07, 44.77, 34.87, 31.88, 29.45, 29.41, 29.32, 27.82, 25.83, 22.66, 14.11; positive electrospray MS m/z 304 [M + H]+ ; HR MS calcd. for C19 H30 NaO2 [M + H]+ : 304.2277. Found: 304.2284.

2.8.2. Data for 1-heptadecyl-6,7-dimethoxy-3,4dihydroisoquinoline (10c) Starting from amide 9c (0.90 g) compound 10c (0.47 g, yield 55.3%) was isolated as a yellow oil following the procedure 2.8. 1 H NMR δ 7.02 (s, H-8), 6.71 (s, H-5), 3.93 and 3.91 (two s, 6H, OCH3 ), 3.66 (t, J = 7.7 Hz, 2H-3), 2.75 (t, J = 7.5 Hz, 2H-1 or 2H-4), 2.66 (t, J = 7.7 Hz, 2H-4 or 2H1 ), 1.67 (quintet, J = 7.5 Hz, 2H-2 ), 1.40 (m, 2H3 ), 1.19–1.36 (m, 26H, H-4 , H-5 , H-6 , H-7 , H8 , H-9 , H-10 , H-11 , H-12 , H-13 , H-14 , H15 , H-16 ), 0.88 (t, J = 6.8 Hz, 3H-17 ); 13 C NMR δ 167.12, 150.87, 147.60, 131.82, 122.12, 110.53, 109.06, 56.42, 56.11, 47.08, 36.30, 32.10, 29.70, 29.68, 29.66, 29.64, 29.57, 29.55, 29.46, 29.37, 27.41, 26.09, 22.86, 14.29; positive electrospray MS m/z 430 [M + H]+ . 2.8.3. Data for 1-[(8Z,11Z,14Z)-heptadeca-8, 11,14-trienyl]-6,7-dimethoxy-3,4-dihydroisoquinoline (10f) Starting from amide 9f (0.88 g) compound 10f (0.53 g, yield 62.5%) was isolated as a colorless oil following the procedure 2.8. 1 H NMR δ 6.71 and 6.70 (two s, 2H, H-5 and H-8), 5.35–5.51 (m, 6H, H-8 , H9 , H-11 , H-12 , H-14 , H-15 ), 3.92 and 3.91 (two s, 6H, OCH3 ), 3.88 and 3.73 (two m, 2H-3), 2.78 (m, 4H, 2H-10 , 2H-13 ), 2.63 (m, 4H, 2H-4 and 2H1 ), 2.09 (m, 4H, 2H-7 , 2H-16 ), 1.58 (m, 4H, 2H2 , 2H-6 ), 1.36 (m, 6H, 2H-3 , 2H-4 , 2H-5 ), 0.97 (t, J = 7.0 Hz, 3H-17 ); 13 C NMR δ 164.25, 151.08, 147.39, 132.17, 131.98, 130.23, 128.30, 128.29, 127.76, 127.10, 120.11, 110.42, 108.87, 56.28, 55.97, 47.27, 36.88, 35.28, 29.71, 29.61, 29.11, 27.19, 26.89, 25.68, 25.60, 20.56, 14.29; positive electrospray MS m/z 424 [M + H]+ . 2.8.4. Data for 1-[(4Z,7Z,10Z,13Z)-nonadeca-4, 7,10,13-tetraenyl]-6,7-dimethoxy-3,4-dihydroisoquinoline (10g) The conversion of amide 9g (0.94 g) into imine 10g was effected following the procedure 2.8. The chromatographically pure compound 10g (0.85 g, 94.8% yield) was obtained as very unstable yellow oil. The product without spectral investigations was immediately reduced in the next step into amine 11g.

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

2.9. General procedure for preparation of 1-alk(en)yl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines (11e–11g) and (11c) To a stirred and cooled (0 ◦ C) solution of imine 10e–10f or 10c (1.0 mmol) in ethanol (5 ml), NaBH4 (0.25 g, 6.6 mmol) was added in two portions. After removing of the cooling bath, the reaction mixture was stirred at room temperature for 2 h. Water (10 ml) was then added to the solution and ethanol was evaporated under reduced pressure. The aqueous layer was extracted with three portions (5 ml each) of dichloromethane and the combined organic extracts were washed with brine (10 ml), dried and evaporated. The residue was subjected to column chromatography using 5–8% (v/v) methanol in chloroform as eluent. Compounds 11e–11g and 11c were isolated as pale yellow oils. 2.9.1. Data for 1-octyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (11e) Starting from imine 10e (0.30 g) compound 11e (0.27 g, 88.8% yield) was isolated following the procedure 2.9. 1 H NMR δ 6.62 and 6.57 (two s, 2H, H-5 and H-8), 3.90 (m, H-1), 3.85 and 3.84 (two s, 6H, OCH3 ), 3.23 (dt, 1H, J1 = 12.3, J2 = 5.4 Hz, H3), 2.97 (ddd, 1H, J1 = 12.6, J2 = 7.9, J3 = 5.5 Hz, H3), 2.60–2.80 (m, 2H-4), 2.16 (br s, NH), 1.63–1.78 and 1.46–1.61 (two m, 2H-1 ), 1.14–1.46 (m, 12H, H2 , H-3 , H-4 , H-5 , H-6 , H-7 ), 0.86 (t, J = 7.0 Hz, 3H-8 ); 13 C NMR δ 147.23, 147.16, 131.51, 127.09, 111.73, 109.21, 56.01, 55.83, 55.46, 41.09, 35.85, 31.91, 30.20, 29.70, 29.40, 29.15, 26.27, 22.99, 14.07; positive electrospray MS m/z 306 [M + H]+ ; HR MS calcd. for C19 H32 NO2 [M + H]+ : 306.2433. Found: 306.2444. 2.9.2. Data for 1-heptadecyl-6,7-dimethoxy-1,2,3, 4-tetrahydroisoquinoline (11c) Starting from imine 10c (0.43 g) compound 11c (0.33 g, 77.0% yield) was isolated following the procedure 2.9. 1 H NMR δ 6.60 and 6.57 (two s, 1H8 and 1H-5), 4.03 (dd, J1 = 8.8, J2 = 3.9 Hz, 1H-1), 3.86 and 3.85 (two s, 6H-OCH3 ), 3.48 (br s, NH), 3.30 (dt, 1H), 3.04 (m, 1H) and 2.70–2.86 (m, 2H) (2H-3 and 2H-4), 1.72–1.90 (m, 2H-1 ), 1.58 (quintet, 2H-2 ), 1.18–1.52 (m, 28H, H-3 , H-4 , H-5 , H-6 , H-7 , H-8 , H-9 , H-10 , H-11 , H-12 , H-13 ,

141

H-14 , H-15 , H-16 ), 0.88 (t, J = 6.8 Hz, 3H-17 ); 13 C NMR δ 147.61, 147.43, 129.66, 126.26, 111.63, 109.24, 56.02, 55.86, 55.04, 40.28, 36.01, 35.34, 31.94, 29.77, 29.72, 29.67, 29.65, 29.60, 29.56, 29.42, 29.37, 28.34, 25.94, 25.41, 22.70, 14.13; positive electrospray MS m/z 454 [M + Na]+ , 432 [M + H]+ ; HR MS calcd. for C28 H50 NO2 [M + H]+ : 432.3842. Found: 432.3825. 2.9.3. Data for 1-[(8Z,11Z,14Z)-heptadeca-8,11, 14-trienyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (11f) Starting from imine 10f (0.42 g) compound 11f (0.35 g, 83.2% yield) was isolated following the procedure 2.9. 1 H NMR δ 6.60 and 6.57 (two s, H-8 and H-5), 5.50–5.58 and 5.28–5.44 (two m, 1H and 5H, H-8 , H-9 , H-11 , H-12 , H-14 , H-15 ), 3.97 (m, 1H1), 3.85 (s, 6H-OCH3 ), 3.27 and 3.01 (two m, 2H-4), 2.54–2.86 (m, 6H, 2H-4, 2H-10 , 2H-13 ), 2.07 (m, 4H, 2H-7 , 2H-16 ), 1.70–1.90 (m, 3H), 1.256–1.55 (m, 10H), 0.97 (t, J = 7.5 Hz, 3H-17 ); 13 C NMR δ 147.42, 147.29, 131.97, 130.32, 128.29, 128.26, 127.70, 127.11, 126.71, 124.43, 111.71, 109.20, 56.03, 55.83, 55.42, 40.88, 36.34, 29.80, 29.66, 29.54, 29.31, 28.94, 27.25, 26.17, 25.62, 25.53, 20.56, 14.29. Positive electrospray MS m/z 448 [M + Na]+ , 426 [M + H]+ ;HR MS calcd. for C28 H44 NO2 [M + H]+ : 426.3372. Found: 426.3362. 2.9.4. Data for 1-[(4Z,7Z,10Z,13Z)-nonadeca-4,7, 10,13-tetraenyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline (11g) Starting from imine 10g (0.45 g) compound 11g (0.36 g, 79.1% yield) was isolated following the procedure 2.9. 1 H NMR δ 6.60 and 6.57 (two s, 1H-8 and 1H5), 5.37 (m, 8H, H-4 , H-5 , H-7 , H-8 , H-10 , H-11 , H-13 , H-14 ), 3.85 (s, 6H-OCH3 ), 3.96 (m, 1H-1), 3.22 (br s, NH), 2.52–3.01 (m, 10H, H-3, H-4, H-6 , H-9 , H12 ), 2.00–2.25 (m, 4H, H-3 , H-15 ), 1.45–1.93 (m, 4H, H-1 , H-2 ), 1.15–1.45 (m, 6H, H-16 , H-17 , H-18 ), 0.89 (t, J = 7.0 Hz, 3H-19 ); 13 C NMR δ 147.33, 147.24, 131.14, 130.50, 129.92, 128.57, 128.32, 128.13, 127.89, 127.53, 127.04, 111.76, 109.20, 56.02, 55.84, 55.36, 41.06, 35.96, 31.52, 29.33, 27.23, 26.8, 25.70, 25.65, 22.58, 14.09; LSIMS(+) m/z 474 [M + Na]+ , 452 [M + H]+ ; HR MS calcd. for C30 H45 NNaO2 [M + Na]+ : 474.3348. Found: 474.3371.

142

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

Fig. 2. Some biologically active 1-substitute-1,2,3,4-tetrahydroisoquinoline.

3. Results and discussion Alkaloids and their analogues possessing 1-substituted tetrahydroisoquinoline skeleton include several biologically active compounds as (S)-salsolidine, (S)-calycotomine, (S)-laudanosine, and (S)-xylopinine (Fig. 2). Therefore, the synthesis of these compounds, recently also in stereoselective manner, has attracted much attention of several research groups. Among a variety of methods available for the construction of tetrahydroisoquinoline skeleton, especially two of them seem to be most often applied: the Pictet–Spengler condensation and the Bischler–Napieralski cyclization (Rozwadowska, 1994; Chrzanowska and Rozwadowska, 2004). Both methods involve the use of different starting materials and processes with different intermediates. Planning further in vivo investigations with regioselectively radio-labeled substrates, we found both methods very promising in planned incorporation of the radioactivity into selected parts of the molecule. The Pictet–Spengler reaction is the most frequently used method in the chemistry of isoquinolines. In this process dopamine 1 is reacted, sometimes under very mild biomimetic conditions with the carbonyl compound (often aldehyde), furnishing directly the 1-substituted-1,2,3,4-tetrahydroisoquinoline skeleton. The product contains two phenolic groups that allow the introduction of tritium atoms into the aromatic ring.

We have already successfully applied this approach for the radio-labeling of dopamides and we concluded that N-oleoyl-dopamine (the analogue of compounds 9c, and 9e–9f) had an appreciable ability to cross the blood–brain barrier (Pokorski et al., 2003). Our study suggested a potential pharmacological role for exogenously delivered selected dopamides in helping regulate the brain function and that N-oleoyl-dopamine might enhance the normally limited dopamine transport into the brain, which would be of therapeutic potential in the pathological states characterized by deranged brain neurotransmitter profile. Aldehydes 2a–2d were prepared from commercially available alcohols using the Swern oxidation methodology (Mancuso and Swern, 1981) following the procedure optimized by us for the oxidation of other primary alcohols (Czarnocki et al., 1986).1 Dopamine was then subjected to the Pictet–Spengler reaction with aldehydes 2a–2d in boiling 1-propanol to afford directly 1-substituted-1,2,3,4-tetrahydroisoquinolines 3a–3d in isolated 52–60% yield (Scheme 1). Compounds 3a–3d proved to be relatively prone to aerial oxidation and slow decomposition, probably due to the presence of two phenolic groups and secondary amine functionality. In order to increase the stability of the molecule, both phenolic groups were methylated 1 The conditions of Swern oxidation ensures the stability of very sensitive components.

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

143

Scheme 1. The synthesis of tetrahydroisoquinoline via the Pictet–Spengler reaction.

by a two-step procedure. Thus, the treatment of 3a–3d with an excess of methyl chloroformate in the presence of pyridine gave per-acyl derivatives 4a–4d in fair to good yields after purification by column chromatography and crystallization. The removal of the carbonate protecting groups was performed via ammonolysis under very mild conditions to afford amides 5a–5d that were immediately di-O-methylated with methyl iodide in the presence of potassium carbonate to give final 1-substituted6,7-dimethoxy-1,2,3,4-tetrahydroisoquinolines 6a–6d in good isolated yields. The Bischler–Napieralski cyclization constitutes another important method for the construction of isoquinoline skeleton (Rozwadowska, 1994; Chrzanowska and Rozwadowska, 2004). Starting from different substrates, employing different reagents and going through another types of intermediate compounds, the method provides an important, complementary alternative to the former approach, also in respect of considered labeling experiments. Usually, arylethylamides of carboxylic acids were treated with acidic reagents (e.g., POCl3 , PCl5 ,

polyphosphoric acid) to give 3,4-dihydroisoquinoline or dihydroisoquinolinium salt, subsequently reduced by complex metal hydrides or by hydrogenation to afford 1,2,3,4-tetrahydroisoquinolines. In our case, we started from homoveratrylamine and the appropriate fatty acid 8e–8g to form amides 9e–9g in a mild, BOP-mediated coupling (Czarnocki et al., 1998). This method was chosen to ensure optimal yield of the product and chemical and stereochemical stability of the acid used. Also, the subsequent cyclization was optimized to eliminate unwanted transformations of sensitive parts of the molecules (Scheme 2). Upon treatment with phosphorous pentachloride in dichloromethane at 0 ◦ C, amides 9e–9g gave relatively unstable imines 10e–10g in fair yields in a pure form without any contamination of chlorinated products.2 The imine double bond in compounds 10e–10g gives not only the possibility to introduce the radioactive labeling (e.g. by the reduction with NaB3 H4 ) but also 2 We observed that compounds 10e–10g were quite sensitive towards air oxidation and moisture and should be taken immediately to the next step.

144

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

Scheme 2. The synthesis of tetrahydroisoquinoline via the Bischler–Napieralski reaction.

provides a prochiral environment for the enantioselective synthesis. When reduced with sodium borohydride in ethanol, imines 10e–10g afforded secondary amines 11e–11g in over 80% isolated yields. These compounds appeared quite stable and could be stored without observable decomposition at room temperature except in the case of amine 11g, which should be kept in the cold. The most indicative and significant absorption in the NMR spectra in both series 6a–6d and 11e–11g were attributed to carbon and hydrogen in methoxy groups and the aromatic ring. In the series of amides both signals of proton and the C-1 carbon atoms appeared deshielded in the region 4.9–5.2 and 52.7–55.2 ppm, respectively. Absorptions of methoxy substituents in all final compounds at 55.8–56.1 ppm for 13 C NMR and 3.84–3.95 ppm for 1 H NMR in the form of isolated peaks seem to be quite characteristic and may serve as a future reference for analogues. The interpretation of both 1 H and 13 C NMR spectra in the series of compounds 4a–4d, 5a–5d, and 6a–6d was not straightforward. The inspection of complicated patterns of signals has prompted us to assume the presence of two relatively stable (with respect to the NMR time scale) conformers in CDCl3 solution. It seems quite clear that restricted rotation around the amide bond in all twelve 1-substituted isoquinolinecarboxylates might be responsible for the observed phenomenon. Alternatively, a steric type A interaction in 1,2-arrangement of methoxycarbonyl and alk(en)yl substituents may generate relatively stable rotamers (Eliel and Wilen, 1994).

The conformer ratio in the series of compounds varied from about 1:1 in 4a–4d, through 2:1 in 5a–5d, back to ca. 1:1 in 6a–6d, that reflects the increasing polarity of interacting substituents. Since a temperature dependent 1 H NMR experiments did not give a conclusive answer, we had to rely on the room temperature spectra. Thus, in the case of the spectrum of compound 4a, we observed three pairs of “one-proton” signals: doublet of doublets at 5.05 and 5.17 ppm (H-1 in both conformers), multiplets at 4.25 and 4.03 (H-3), and multiplets at 3.18 and 3.28 ppm (H-3). The integration ratios of all former signals versus the later ones in all three pairs were approximately in the same order (6:5). On the other hand, the singlets at 3.90 and 3.89 ppm (OCOOCH3 , four methyl groups) were located too close to each other to allow direct integration comparison. The same was also observed in the case of signals at 3.71 and 3.72 ppm (NCOOCH3 ), as well as for signals at 7.02 and 7.00 ppm (H-5 and H-8).

4. Conclusions Two series of novel tetrahydroisoquinoline derivatives bearing at C-1 atom a carbon chain derived from fatty acids were prepared employing two complementary synthetic methodologies: the Pictet–Spengler condensation and the Bischler–Napieralski cyclization. The ability to use both methods allows our further experiments for various labeling of the final 1-

I. Matuszewska et al. / Chemistry and Physics of Lipids 135 (2005) 131–145

substituted-1,2,3,4-tetrahydroquinolines for biological studies. These will involve the determination of the brain uptake and distribution of lipophilic dopamine and isoquinoline derivatives that can freely penetrate the blood–brain barrier and serve as slow-release precursor of dopamine which play a crucial role in developing different pathologic states like Parkinson’s disease. References Aurell, M.J., Ceita, L., Mestres, R., Tortajada, A., 1997. Dienodiolates of unsaturated carboxylic acids in synthesis. Aldehydes and ketones from alkyl halides, by ozonolysis of ␤,␥-unsaturated ␣alkyl carboxylic acids. The role of a tertiary amine in the cleavage of ozonides. Tetrahedron 53, 10883–10898. Bezuglov, V., Bobrov, M., Gretskaya, N., Gonchar, A., Zinchenko, G., Melck, D., Bisogno, T., Di Marzo, V., Kuklev, D., Rossi, J.-C., Vidal, J.P., Durand, T., 2001. Synthesis and biological evaluation of novel amides of polyunsaturated fatty acids with dopamine. Bioorg. Med. Chem. Lett. 11, 447–449. Bezuglov, V.V., Manevich, Y., Archakov, A.V., Bobrov, M.Yu., Kuklev, D.V., Petrukhina, G.N., Makarov, V.A., Buznikov, G.A., 1997. Artifically functionalized polyenoic fatty acids as new lipid bioregulators. Russ. J. Bioorg. Chem. 23, 190– 198. Bisogno, T., Katayama, K., Melck, D., Ueda, N., De Petrocellis, L., Yamamoto, S., Di Marzo, V., 1998. Biosynthesis and degradation of bioactive fatty acid amides in human breast cancer and rat pheochromocytoma cells. Implications for cell proliferation and differentiation. Eur. J. Biochem. 254, 634–642. Boger, D.L., Henriksen, S.J., Cravatt, B.F., 1998. Oleamide: an endogenous sleep-inducing lipid and prototypical member of a new class of biological signaling molecules. Curr. Pharm. Design 4, 303–314. Chrzanowska, M., Rozwadowska, M.D., 2004. Asymmetric synthesis of isoquinoline alkaloids. Chem. Rev. 7, 3341–3370. Czarnocki, Z., Matuszewska, M.P., Matuszewska, I., 1998. Highly efficient synthesis of fatty acid dopamides. Org. Prep. Proc. Int. 30, 699–702. Czarnocki, Z., MacLean, D.B., Szarek, W.A., 1986. Asymmetric synthesis of isoquinoline alkaloids: (R)- and (S)-ethoxycarbonyl-1formyl-6,7-dimethoxy-1,2,3-4-tetrahydroisoquinoline as versatile precursors. Bull. Soc. Chim. Belg. 95, 749–770. De Petrocellis, L., Melck, D., Bisogno, T., Di Marzo, V., 2000. Endocannabinoids and fatty acid amides in cancer, inflammation and related disorders. Chem. Phys. Lipids 108, 191–209. Easton, C.J., Xia, L., Pitt, M.J., Ferrante, A., Poulos, A., Rathjen, D.A., 2001. Polyunsaturated nitroalkanes and nitro-substituted fatty acids. Synthesis 3, 451–457.

145

Eliel, E.L., Wilen, S.H., 1994. Sterochemistry of Organic Compounds. Wiley–Interscience, New York, p. 738. Hillard, C.J., Wilkison, D.M., Edgemond, W.S., Campbell, W.B., 1995. Characterization of the kinetics and distribution of Narachidonylethanolamine (anandamide) hydrolysis by rat brain. Biochim. Biophys. Acta 1257, 249–256. Kornblum, N., Erickson, A.S., Kelly, W.J., Henggeler, B., 1982. Conversion of nitro paraffins into aldehydes and ketones. J. Org. Chem. 47, 4534–4538. Mancuso, A.J., Swern, D., 1981. Activated dimethyl sulfoxide: useful reagent for synthesis. Synthesis, 165–185. Nagatsu, T., 2002. Amine-related neurotoxins in Parkinson’s disease—past, present, and future. Neurotoxicol. Teratol. 24, 565–569. Nagatsu, T., 1997. Isoquinoline neurotoxins in the brain and Parkinson’s disease. Neurosci. Res. 29, 99–111. Naoi, M., Maruyama, W., Dostert, P., Hashizume, Y., Nakahara, D., Takahashi, T., Ota, M., 1996. Dopamine-derived endogenous 1(R),2(N)-dimethyl-6.7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, N-methyl-(R)-salsolinol, induced parkinsonism in rat: biochemical, pathological and behavioral studies. Brain Res. 709, 285–295. Pokorski, M., Matysiak, Z., 1998. Fatty acid acylation of dopamine in the carotid body. Med. Hypoth. 50, 131–133. Pokorski, M., Matysiak, Z., Marczak, M., Ostrowski, R.P., Kapu´sci´nski, A., Matuszewska, I., Ka´nska, M., Czarnocki, Z., 2003. Brain uptake of radiolabeled N-oleoyl-dopamine in the rat. Drug Dev. Res. 60, 217–224. Rozwadowska, M.D., 1994. Recent progress in the enantioselective synthesis of isoquinoline alkaloids. Heterocycles 39, 903–931. Shashoua, V.E., Hesse, G.W., 1996. N-Docosahexaenoyl, 3hydroxytyramine: a dopaminergic compound that penetrates the blood–brain barrier and suppresses appetite. Life Sci. 58, 1347–1357. Siwicka, A., Wojtasiewicz, K., Leniewski, A., Maurin, J.K., Czarnocki, Z., 2002. Diastereoselective synthesis of some ␤carboline derivatives from l-amino acids. Tetrahedron: Asymmetry 13, 2295–2297. Syper, L., Młochowski, J., 1984. A convenient oxidation of halomethylarenes and alcohols to aldehydes with dimethyl selenoxide and potassium benzenselenite. Synthesis 9, 747– 752. Taber, D.F., Amedio, J.C., Yung, K.-Y., 1987. P2 O5 /DMSO/ triethylamine (PDT): a convenient procedure for oxidation of alcohols to ketones and aldehydes. J. Org. Chem. 52, 5621–5622. Tsay, S.-C., Robl, J.A., Hwu, J.R., 1990. New method for the selective reduction of amides. J. Chem. Perkin. Trans. 1 (3), 757–759. Zhu, W., Ma, Y.L., Stefano, G.B., 2002. Presence of isoquinoline alkaloids in molluscan ganglia. Neuroendocrinol. Lett. 23, 329–334. Zi´ołkowski, M., Czarnocki, Z., 2000. The use of l-(+)-tartaric acid in the enantioselective synthesis of isoquinoline alkaloids. Tetrahedron Lett. 41, 1963–1966.