- Email: [email protected]
New Chiral Calixarene Derivatives: Syntheses and Their Chiral Recognition Toward Amino Acids by UV-Vis Spectroscopy
Available online at www.sciencedirect.com
CHEM. RES. CHINESE UNIVERSITIES 2008, 24( I), 106-109 Article ID 1005-9040(2008)-0 1- 106-04
ScienceDirect
New Chiral Calixarene Derivatives: Syntheses and Their Chiral Recognition Toward Amino Acids by UV-Vis Spectroscopy GU Jin-ying', HE Wan-ping', SHI Xian-fa'* and JI Liang-nian"* 1. Department of Chemistry, Tongji University, Shanghai 200092, P R. China; 2. Department of Chemistry, Sun Yat-sen University, Guangzhou 510275, P: R. China
Abstract Three novel types of chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral units to parent calixarenes. Their chiralities were confirmed by rotational analysis. Chiral recognition properties of these host compounds towards L- and D-threonine were studied by UV-Vis spectroscopy. The results indicated that calixarene derivatives 5 and 8 exhibited good chiral recognition capabilities toward L- or D-threonine. Although calixarene derivative 10 had no evident chiral recognition ability, the supramolecules of calixarene derivative 10 with L- or D-threonine showed a hypochromic effect or hyperchromic effect respectively. Therefore, calixarene derivative 10 might serve as a good chiral UV-indicator. Keywords Chiral calixarene; Synthesis; Amino acid; Chiral recognition
I Introduction
derivative^"^-'^^ but the study about chiral recognition of calixarene derivatives toward amino acids is rare. Three new chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral alanine to the parent calixarene skeleton in this article. Then their structures were characterized and their chiralities confirmed. Their host-guest interaction toward chiral threonine was studied by UV-Vis spectroscopy.
Calixarenes and their derivatives-one of the most important artificial host molecules-have good molecular recognition abilities to many cations, anions, neutral molecules, and biomolecules, such as, amino acids and nu~leotides"-~].In recent years chiral calixarenes have attracted increasing attention because of their potential applications in chiral recognition, sepa2 Experimental ration of enantiomers, and asymmetric 2.1 Instruments and Reagents Because of its inherent symmetric structure, calixarene cannot be used for chiral recognition directly. Melting points were obtained with a WRS-19 Therefore, modifying the structure of cali- xarenes Model Digital Melting Point apparatus. Infrared first, to provide chiral property in the molecules, is a spectra were recorded on a NEXUS 912A0446 Movaluable investigation. del spectrophotometer. UV-Vis spectra were meaGenerally chiral calixarenes can be achieved sured on an Agilent 8453 UV-Vis spectrophotometer. by three approaches: (1) introducing different substi- Elemental analyses, NMR spectra ESI-MS were detuents at the lower or upper rims of the calixarene ske- termined by Shanghai lnstitute of Organic Chemistry, leton, to destroy its inherent symmetric structure or Chinese Academy of Sciences. All chemicals used for produce an asymmetric array of achiral residues on the the synthesis were got from the market. Besides calixarene skeleton by chemical modifi~ation[~-'~];L-alanine, L-alanine ethyl ether hydrochloride, and (2) immobilizing calixarene to an asymmetric confor- threonine were biochemical reagents, all the other mation" 0.131., (3) introducing chiral residues into the chemicals were of analytical grade. calixarene skeleton d i r e ~ t l y [ l ~ - ' ~Thereby, ]. introducing chiral residues directly to the parent calixarene, 2.2 Synthesis of Compounds which is an efficient method. Thus far, there have been A multistep route, as shown in Scheme 1, was many reports about the synthesis of chiral calixarene chosen for the synthesis of these new types of chiral
* Corresponding author. E-mail: [email protected] Received June I, 2007; accepted June 25,2007. Supported by the National Natural Science Foundation of China(No. 20472065). Copyright Q 2008, Jilin University. Published by Elsevier Limited. All rights reserved.
No. 1
GU Jin-ying et al.
107
calixarene derivatives.
'6 /
NaOH
+ HCHOT
@ -@ ' AICIx
CH2 1
CH2
&
OH
OH
OH
BrCH.COOEi * K~COI.CHCN
OH
.
SnClr
3
2
1
CI:CHOCHa
OR
COOH H''' k C H ,
CHO
I
L-Alanmc *
KOH 4
R=CH2COOEt
5
6
2
6
H~N-SOIH H2N-S03Ht NaCIO: *
7
e!?J OH
0
8
7
b
H.--@;PCHKH~ H..-$g03PCHKH~
I.-Alaninc ethyl ether hy drochlonde drochlonde,
N(C2Hch
9
10
Scheme 1 Synthesis routes of title compounds
The reactions of each of the p-tert-butyl phenols with formaldehyde, under nitrogen, provided p-tertbutyl calix[4] arenes lL2"'. The dealkylation of compound 1 carried out by AlC13, led to compound 2'2'1. Next, compound 2 was treated with ethyl bromoacetate in the presence of K2C03 in CH3CN, to get the diesterified compound 3. The purpose of esterification in the lower rim of the calixarene was to decrease the activities of their para points, so as to control the number of aldehydes when introducing substituents in the upper rim in the subsequent reaction. Compound 3 (m.p. 179.9 "C was characterized by IR, 'H NMR and ESI-MS. Compound 3(0.798 g) was dissolved in 25 mL of chloroform, then cooled down to 15 "C, in which 1.82 mL anhydrous SnC14 and 0.346 mL of 1, l-dichloromethyl ether were added rapidly. The light red reaction mixture was stirred at -10 "C for 1 h till the aubergine dope appeared. Next, water was added and stirred continuously at room temperature
till the dope disappeared and the mixture turned colorless. The organic phase was washed with water and distilled in vacuum to remove the solvent, affording a yellow oil, to which acetone was added and the white precipitate was then filtered and dried in vacuum. The crude product was purified by column chromatography[dripping liquid: V(petro1eum ether) V(ethy1 acetate)=7 : 31 to give a white compound 4. m.p. 168-170 "C; ESI-MS, m/z: 647.3 (M+Na)', 663.2(M+K)+; IR(KBr), B /cm-': 3405s (Ar-OH), 175Os(C=O ester), 1685s(Ar--CHO aldehyde; 'H NMR(CDCI3), S: 9.77(s, IH, CHO) , 8.65(s, lH, Ar-OH), 8.63(s, lH, Ar-OH), 7.61(s, 2H, Ar-H), 6.79-6.92(m, 9H, Ar-H), 4.354.73(m, 4H, -CH2-CH3), 3.39-3.89(m, 8H, Ar-CH2-Ar), 2.15(s, 4H, ArO-CH2), 1.35(t, 6H, -CH3). L-Alanine of 0.178 g and 0.112 g of potassium hydroxide were dissolved in 50 mL of methanol in advance. Compound 4 (0.652 g) was dissolved in a
108
CHEM. RES. CHINESE UNIVERSITIES
trifle of methanol, in which the earlier-mentioned L-alanine and KOH mixed solution was added dropwise. Then a molecular sieve was added to absorb water. The reaction mixture was stirred under nitrogen at 40 "C for 8 h. Gradually the solution turned into light yellow or brown. Then the solution was distilled in vacuum to remove the solvent, affording a black yellow crude product. It was purified by column chromatography [dripping liquid: V(petroleum ether) : V(ethyl acetate)=5 : 13 to give compound 5. ESI-MS, m/z: 668.3(M+H)+; IR(KBr), O/cm-': 3078m, 1619s(C = N-C, Schiff base), 1736w(C =0, ester); elemental anal.(%) calcd. for C38H37010N:C 68.36, H 5.55, N 2.10; found: C 68.29, H 5.47, N 2.25. Compound 8 was synthesized by a similar method used for compound 5. First compound 6 was prepared by the reaction of compound 2 and benzoyl chloride. It was characterized by IR, ESI-MS and 'H NMR. Next, Compound 6 was treated with hexamethylenamine and trifluoacetic acid to give compound 7. It was characterized by IR and ESI-MS. Then, the reaction of compound 7 with L-alanine and potassium hydroxide in acetonitrile gave compound 8. ESI-MS m/z: 875.6(M+K+H)+, 893.2(M+K+Na+H)+; Schiff Base), IR(KBr), ij/cm-' : 3077m(C = N-C, 1623s(C = N-C, Schiff base); elemental anal.(%) calcd. for CS3H41O9N:C 7 6.17, H 4.91, N 1.68; found: C 76.23, H 5.08, N 1.34. Aminosulfonic acid of 0.1 g and 0.1 g of NaCIOz were dissolved in 3 mL of water in advance. Compound 7(0.382 g) was dissolved in 100 mL of a mixture of chloroform and acetone(vo1ume ratio 1 : l), to which the earlier-mentioned aminosulfonic acid and NaClOz mixed solution was added. The reaction mixture was stirred at room temperature for 4 h, then distilled in vacuum to remove the solvent. To the residue was added 10 mL of 2 m o l L hydrochloric acid, which was then filtered and dried, affording compound 9, whose structure was confirmed by ESI-MS. Compound 9(0.39 g) was dissolved in 15 mL of anhydrous CH2C12, to which was added 0.35 g of HBTU. It was then stirred to form a suspended mixture, in which 0.15 g of L-alanine ethyl ether hydrochloride and 0.2 mL of triethylamine were added. The mixture was stirred at room temperature for 4 h, after which, 10 mL of 1 mol/L hydrochloric acid was added. The organic phase was
Vo1.24
washed with 10 mL of water, 10 mL of NaHC03(5%), and 10 mL of water respectively, and then dried with anhydrous MgS04 for 12 h. It was distilled to remove the solvent and dried in vacuum, affording the crude product. It was purified by column chromatography[dripping liquid: V(petro1eum ether) : V(ethyl acetate)=5 : 13 to give compound 10. ESI-MS, m/z: 763.3(M-NC5Hlo02)+; IR(KBr), ij /cm-': 3425m (Ar-OH), 1728s(C=O, ester), 1672, 1560, 1320 (-CONHR, I, 11, 111 belts); elemental anal.(%) calcd. for C55H45010N:C 75.09, H 5.12, N 1.59; found: C 75.14, H 5.04, N 1.68.
3 Results and Discussion 3.1 Polarimetric Analysis of Compounds 5, 8, and 10 To confirm the chirality of compounds 5, 8, and 10, their rotatory power was measured with a polarimeter. Compound 5 and compound 8 were dissolved in methanol; compound 10 was dissolved in tetrahydrofuran. The results show that the three novel compounds were all optically active. Their specific rotation was [a]=-19.5" for compound 5; [a]=-21.8" for compound 8; and [a]=-19.3" for compound 10. In other words, they all showed levo-rotation. 3.2 Chiral Recognition of the Three Chiral Compounds to Amino Acids
In this article UV-Vis spectroscopy was used for the investigation of the chiral recognition between the hosts 5, 8, 10 and the guest amino acid. Chiral threonine was selected as the guest molecule here. When L-theroine or D-threonine, with equal concentration, was added to the solution of compound 5 respectively, different changes were observed, as shown in Fig.l(A). To observe the changes of the absorption peak clearly, the graph was enlarged and put on the top right corner. The shape of the absorption curve's mixed systems and the position of the maximum absorption were much the same as that of compound 5 ; but the absorption intensity at the maximum absorption wavelength(A=357 nm) of the S+L-Thr system increased evidently, showing a hyperchromic effect, whereas, the absorption intensity of the S+D-Thr system had no significant changes compared to the primal value of compound 5 . This clearly showed that compound 5 could react with L-threonine, resulting in an evident hyper-
GU Jin-ying et al.
No.1
chromism because threonine had no absorbance when k-220 nm, and could recognize L-threonine from the
-
0.0 300
400
500
600
700
800
enantiomorphous L-threonine.
mixture
of
:'i
D-threonine
and
-..
P
06
04 02
300
400
,Unm
Fig.1
109
500 600 i./nni
800
700
;
200 240
280 120 360 400 A/NII
0.0 ).. , I 200 300 400 500 600 700 800 iJnm I
Interaction between compound 5(A), 8(B), 1O(C) and L-Thr or D-Thr
The concentration of compounds 5 and 10 was 2 ~ 1 0mol/L. '~ the concentration of compounds 8 and 10 was 5 ~ 1 mol/L 0 ~
In the same way, the recognition property of compound 8 toward threonine was examined, as shown in Fig.l(B). The results showed that the absorption intensity at the maximum absorption wavelength(il=292 nm) of 8+D-Thr system increased evidently, showing a hyperchromic effect, whereas, the absorption intensity of 8+L-Thr system had no significant change compared to the primal value of compound 8. It was shown that compound 8 had chiral recognition capability toward D-threonine, and could recognize D-threonine from the enantiomorphous mixture of D- threonine and L-threonine. The recognition property of compound 10 toward L-threonine or D-threonine is shown in Fig. 1(C) Compared to those of compounds 5 and 8, the absorption intensity at the maximum absorption wavelength(il=239 nm) of lO+D-Thr system increased evidently, showing a hyperchromic effect, whereas, that of lO+L-Thr system decreased evidently, showing a hypochromic effect . These were all compared with the primal value of compound 10. These results indicated that the interaction between compound 10 and D-threonine or L-threonine did occur, but the products had different E. It was seen that compound 10 did not show chiral selectivity, but this could make it a practical UV-indicator for D- and L-threonine, which could be used to determine or indicate the chiral form of theronine.
References [I]
Gustche C. D., Calixarenes, 'The Royal Society of Chemistry, Cambridge, 1989
Molenveld P., Engbersen J. F., Reinhoudt D. N.,Chem. SOC.Rev., 2000,29,75
Memon S., Yilmaz M., J. Mol. Struct., 2001, 595, 101 Zhu C. J., Yuan C. Y., Lu Y.,Synlett, 2006,s. 1221 Li S. Y.,Zheng Q.Y.,Chen C. F., el al., Tetrahedron. Asymmefiy, 2005,16,2816
Liu F., Lu G. Y.,He W. J., el al., Thin Solid Films, 2004, 468, 244 He Y.B., Xiao Y.J., Meng L. Z., Tetrahedron Letters, 2002,43,6249 Jennings K., Diamond D., Analyst, 2001, 126, 1063
Nomura E., Takagaki M., Nakaoka C., et al., Journal of Organic Chemistry, 1999,64,315 I Arimura T., Kawabata H., Matsuda T., ef al., Journal of Organic Chemistry, 1991,56,56
Narumi F., Hattori T., Tetrahedron. 2004, 60,7827 Reddy A., Gutsche C. D.,Journal of Organic Chemistry, 1993, 58, 32456
Ito K., Noike M., Ohba Y.,Journal of Organic Chemistry, 2002, 67, 7519
Paula M., Jose R. A., Tetrahedron, 2001,57,6977 Blanda M. T., Edwards L., Salazar R., e/ al., Tetrahedron Letters, 2006,47,708 I
Nero P.,Bottino A,, Geraci C., e t a / , Tetrahedron:Asymmetry, 1996, 7 , 17 Pena M. S., Zhang Y. L., Thibodeaux S . , et al., Tetrahedron Letters, 1996,37,5841
Yuan H. S., Zhang Y., Hou Y. J., et ul., Tetrahedron, 2000, 56, 961 I Yuan H. S.,Huang 2. T., Tetrahedron:Asymmetry, 1999, 10.429 Cherenok S., Vovk A,, Muravyova l., eta/.,Organic Letters, 2006, 8, 549
Murakami Y., Hayashida O.,Nagai Y.,J Am. Chem. Soc., 1994,116, 2611 Karakaplan M., Aral T., Tetrahedron-Asymmetry, 2005,6,2119 Ciuo
W.,Wang J., Wang Ch., et al., Tetrahedron Letters, 2002, 43,
5665
Gustche C. D., Iqbal M., Org. Synth., 1990, 68,234 Gustche C. D., Levine J. A,, J. Am. Chem. Soc., 1982,104,2652
CHEM. RES. CHINESE UNIVERSITIES 2008, 24( I), 106-109 Article ID 1005-9040(2008)-0 1- 106-04
ScienceDirect
New Chiral Calixarene Derivatives: Syntheses and Their Chiral Recognition Toward Amino Acids by UV-Vis Spectroscopy GU Jin-ying', HE Wan-ping', SHI Xian-fa'* and JI Liang-nian"* 1. Department of Chemistry, Tongji University, Shanghai 200092, P R. China; 2. Department of Chemistry, Sun Yat-sen University, Guangzhou 510275, P: R. China
Abstract Three novel types of chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral units to parent calixarenes. Their chiralities were confirmed by rotational analysis. Chiral recognition properties of these host compounds towards L- and D-threonine were studied by UV-Vis spectroscopy. The results indicated that calixarene derivatives 5 and 8 exhibited good chiral recognition capabilities toward L- or D-threonine. Although calixarene derivative 10 had no evident chiral recognition ability, the supramolecules of calixarene derivative 10 with L- or D-threonine showed a hypochromic effect or hyperchromic effect respectively. Therefore, calixarene derivative 10 might serve as a good chiral UV-indicator. Keywords Chiral calixarene; Synthesis; Amino acid; Chiral recognition
I Introduction
derivative^"^-'^^ but the study about chiral recognition of calixarene derivatives toward amino acids is rare. Three new chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral alanine to the parent calixarene skeleton in this article. Then their structures were characterized and their chiralities confirmed. Their host-guest interaction toward chiral threonine was studied by UV-Vis spectroscopy.
Calixarenes and their derivatives-one of the most important artificial host molecules-have good molecular recognition abilities to many cations, anions, neutral molecules, and biomolecules, such as, amino acids and nu~leotides"-~].In recent years chiral calixarenes have attracted increasing attention because of their potential applications in chiral recognition, sepa2 Experimental ration of enantiomers, and asymmetric 2.1 Instruments and Reagents Because of its inherent symmetric structure, calixarene cannot be used for chiral recognition directly. Melting points were obtained with a WRS-19 Therefore, modifying the structure of cali- xarenes Model Digital Melting Point apparatus. Infrared first, to provide chiral property in the molecules, is a spectra were recorded on a NEXUS 912A0446 Movaluable investigation. del spectrophotometer. UV-Vis spectra were meaGenerally chiral calixarenes can be achieved sured on an Agilent 8453 UV-Vis spectrophotometer. by three approaches: (1) introducing different substi- Elemental analyses, NMR spectra ESI-MS were detuents at the lower or upper rims of the calixarene ske- termined by Shanghai lnstitute of Organic Chemistry, leton, to destroy its inherent symmetric structure or Chinese Academy of Sciences. All chemicals used for produce an asymmetric array of achiral residues on the the synthesis were got from the market. Besides calixarene skeleton by chemical modifi~ation[~-'~];L-alanine, L-alanine ethyl ether hydrochloride, and (2) immobilizing calixarene to an asymmetric confor- threonine were biochemical reagents, all the other mation" 0.131., (3) introducing chiral residues into the chemicals were of analytical grade. calixarene skeleton d i r e ~ t l y [ l ~ - ' ~Thereby, ]. introducing chiral residues directly to the parent calixarene, 2.2 Synthesis of Compounds which is an efficient method. Thus far, there have been A multistep route, as shown in Scheme 1, was many reports about the synthesis of chiral calixarene chosen for the synthesis of these new types of chiral
* Corresponding author. E-mail: [email protected] Received June I, 2007; accepted June 25,2007. Supported by the National Natural Science Foundation of China(No. 20472065). Copyright Q 2008, Jilin University. Published by Elsevier Limited. All rights reserved.
No. 1
GU Jin-ying et al.
107
calixarene derivatives.
'6 /
NaOH
+ HCHOT
@ -@ ' AICIx
CH2 1
CH2
&
OH
OH
OH
BrCH.COOEi * K~COI.CHCN
OH
.
SnClr
3
2
1
CI:CHOCHa
OR
COOH H''' k C H ,
CHO
I
L-Alanmc *
KOH 4
R=CH2COOEt
5
6
2
6
H~N-SOIH H2N-S03Ht NaCIO: *
7
e!?J OH
0
8
7
b
H.--@;PCHKH~ H..-$g03PCHKH~
I.-Alaninc ethyl ether hy drochlonde drochlonde,
N(C2Hch
9
10
Scheme 1 Synthesis routes of title compounds
The reactions of each of the p-tert-butyl phenols with formaldehyde, under nitrogen, provided p-tertbutyl calix[4] arenes lL2"'. The dealkylation of compound 1 carried out by AlC13, led to compound 2'2'1. Next, compound 2 was treated with ethyl bromoacetate in the presence of K2C03 in CH3CN, to get the diesterified compound 3. The purpose of esterification in the lower rim of the calixarene was to decrease the activities of their para points, so as to control the number of aldehydes when introducing substituents in the upper rim in the subsequent reaction. Compound 3 (m.p. 179.9 "C was characterized by IR, 'H NMR and ESI-MS. Compound 3(0.798 g) was dissolved in 25 mL of chloroform, then cooled down to 15 "C, in which 1.82 mL anhydrous SnC14 and 0.346 mL of 1, l-dichloromethyl ether were added rapidly. The light red reaction mixture was stirred at -10 "C for 1 h till the aubergine dope appeared. Next, water was added and stirred continuously at room temperature
till the dope disappeared and the mixture turned colorless. The organic phase was washed with water and distilled in vacuum to remove the solvent, affording a yellow oil, to which acetone was added and the white precipitate was then filtered and dried in vacuum. The crude product was purified by column chromatography[dripping liquid: V(petro1eum ether) V(ethy1 acetate)=7 : 31 to give a white compound 4. m.p. 168-170 "C; ESI-MS, m/z: 647.3 (M+Na)', 663.2(M+K)+; IR(KBr), B /cm-': 3405s (Ar-OH), 175Os(C=O ester), 1685s(Ar--CHO aldehyde; 'H NMR(CDCI3), S: 9.77(s, IH, CHO) , 8.65(s, lH, Ar-OH), 8.63(s, lH, Ar-OH), 7.61(s, 2H, Ar-H), 6.79-6.92(m, 9H, Ar-H), 4.354.73(m, 4H, -CH2-CH3), 3.39-3.89(m, 8H, Ar-CH2-Ar), 2.15(s, 4H, ArO-CH2), 1.35(t, 6H, -CH3). L-Alanine of 0.178 g and 0.112 g of potassium hydroxide were dissolved in 50 mL of methanol in advance. Compound 4 (0.652 g) was dissolved in a
108
CHEM. RES. CHINESE UNIVERSITIES
trifle of methanol, in which the earlier-mentioned L-alanine and KOH mixed solution was added dropwise. Then a molecular sieve was added to absorb water. The reaction mixture was stirred under nitrogen at 40 "C for 8 h. Gradually the solution turned into light yellow or brown. Then the solution was distilled in vacuum to remove the solvent, affording a black yellow crude product. It was purified by column chromatography [dripping liquid: V(petroleum ether) : V(ethyl acetate)=5 : 13 to give compound 5. ESI-MS, m/z: 668.3(M+H)+; IR(KBr), O/cm-': 3078m, 1619s(C = N-C, Schiff base), 1736w(C =0, ester); elemental anal.(%) calcd. for C38H37010N:C 68.36, H 5.55, N 2.10; found: C 68.29, H 5.47, N 2.25. Compound 8 was synthesized by a similar method used for compound 5. First compound 6 was prepared by the reaction of compound 2 and benzoyl chloride. It was characterized by IR, ESI-MS and 'H NMR. Next, Compound 6 was treated with hexamethylenamine and trifluoacetic acid to give compound 7. It was characterized by IR and ESI-MS. Then, the reaction of compound 7 with L-alanine and potassium hydroxide in acetonitrile gave compound 8. ESI-MS m/z: 875.6(M+K+H)+, 893.2(M+K+Na+H)+; Schiff Base), IR(KBr), ij/cm-' : 3077m(C = N-C, 1623s(C = N-C, Schiff base); elemental anal.(%) calcd. for CS3H41O9N:C 7 6.17, H 4.91, N 1.68; found: C 76.23, H 5.08, N 1.34. Aminosulfonic acid of 0.1 g and 0.1 g of NaCIOz were dissolved in 3 mL of water in advance. Compound 7(0.382 g) was dissolved in 100 mL of a mixture of chloroform and acetone(vo1ume ratio 1 : l), to which the earlier-mentioned aminosulfonic acid and NaClOz mixed solution was added. The reaction mixture was stirred at room temperature for 4 h, then distilled in vacuum to remove the solvent. To the residue was added 10 mL of 2 m o l L hydrochloric acid, which was then filtered and dried, affording compound 9, whose structure was confirmed by ESI-MS. Compound 9(0.39 g) was dissolved in 15 mL of anhydrous CH2C12, to which was added 0.35 g of HBTU. It was then stirred to form a suspended mixture, in which 0.15 g of L-alanine ethyl ether hydrochloride and 0.2 mL of triethylamine were added. The mixture was stirred at room temperature for 4 h, after which, 10 mL of 1 mol/L hydrochloric acid was added. The organic phase was
Vo1.24
washed with 10 mL of water, 10 mL of NaHC03(5%), and 10 mL of water respectively, and then dried with anhydrous MgS04 for 12 h. It was distilled to remove the solvent and dried in vacuum, affording the crude product. It was purified by column chromatography[dripping liquid: V(petro1eum ether) : V(ethyl acetate)=5 : 13 to give compound 10. ESI-MS, m/z: 763.3(M-NC5Hlo02)+; IR(KBr), ij /cm-': 3425m (Ar-OH), 1728s(C=O, ester), 1672, 1560, 1320 (-CONHR, I, 11, 111 belts); elemental anal.(%) calcd. for C55H45010N:C 75.09, H 5.12, N 1.59; found: C 75.14, H 5.04, N 1.68.
3 Results and Discussion 3.1 Polarimetric Analysis of Compounds 5, 8, and 10 To confirm the chirality of compounds 5, 8, and 10, their rotatory power was measured with a polarimeter. Compound 5 and compound 8 were dissolved in methanol; compound 10 was dissolved in tetrahydrofuran. The results show that the three novel compounds were all optically active. Their specific rotation was [a]=-19.5" for compound 5; [a]=-21.8" for compound 8; and [a]=-19.3" for compound 10. In other words, they all showed levo-rotation. 3.2 Chiral Recognition of the Three Chiral Compounds to Amino Acids
In this article UV-Vis spectroscopy was used for the investigation of the chiral recognition between the hosts 5, 8, 10 and the guest amino acid. Chiral threonine was selected as the guest molecule here. When L-theroine or D-threonine, with equal concentration, was added to the solution of compound 5 respectively, different changes were observed, as shown in Fig.l(A). To observe the changes of the absorption peak clearly, the graph was enlarged and put on the top right corner. The shape of the absorption curve's mixed systems and the position of the maximum absorption were much the same as that of compound 5 ; but the absorption intensity at the maximum absorption wavelength(A=357 nm) of the S+L-Thr system increased evidently, showing a hyperchromic effect, whereas, the absorption intensity of the S+D-Thr system had no significant changes compared to the primal value of compound 5 . This clearly showed that compound 5 could react with L-threonine, resulting in an evident hyper-
GU Jin-ying et al.
No.1
chromism because threonine had no absorbance when k-220 nm, and could recognize L-threonine from the
-
0.0 300
400
500
600
700
800
enantiomorphous L-threonine.
mixture
of
:'i
D-threonine
and
-..
P
06
04 02
300
400
,Unm
Fig.1
109
500 600 i./nni
800
700
;
200 240
280 120 360 400 A/NII
0.0 ).. , I 200 300 400 500 600 700 800 iJnm I
Interaction between compound 5(A), 8(B), 1O(C) and L-Thr or D-Thr
The concentration of compounds 5 and 10 was 2 ~ 1 0mol/L. '~ the concentration of compounds 8 and 10 was 5 ~ 1 mol/L 0 ~
In the same way, the recognition property of compound 8 toward threonine was examined, as shown in Fig.l(B). The results showed that the absorption intensity at the maximum absorption wavelength(il=292 nm) of 8+D-Thr system increased evidently, showing a hyperchromic effect, whereas, the absorption intensity of 8+L-Thr system had no significant change compared to the primal value of compound 8. It was shown that compound 8 had chiral recognition capability toward D-threonine, and could recognize D-threonine from the enantiomorphous mixture of D- threonine and L-threonine. The recognition property of compound 10 toward L-threonine or D-threonine is shown in Fig. 1(C) Compared to those of compounds 5 and 8, the absorption intensity at the maximum absorption wavelength(il=239 nm) of lO+D-Thr system increased evidently, showing a hyperchromic effect, whereas, that of lO+L-Thr system decreased evidently, showing a hypochromic effect . These were all compared with the primal value of compound 10. These results indicated that the interaction between compound 10 and D-threonine or L-threonine did occur, but the products had different E. It was seen that compound 10 did not show chiral selectivity, but this could make it a practical UV-indicator for D- and L-threonine, which could be used to determine or indicate the chiral form of theronine.
References [I]
Gustche C. D., Calixarenes, 'The Royal Society of Chemistry, Cambridge, 1989
Molenveld P., Engbersen J. F., Reinhoudt D. N.,Chem. SOC.Rev., 2000,29,75
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