Longipinene derivatives from Stevia origanoides

Vol.32,No 5, pp. 1219-1223, 1993 Pnnted in Great Britain.

0031-9422/93 .S6.00+0.00 Q 1993PergamonPressLtd

Phytochemistry.

LONGIPINENE

DERIVATIVES

FROM STE VIA ORIGANOIDES

CARLOSM. CERDA-GARCIA-ROJAS,EUGENIO SANCHEZ-ARREOLA, PEDRO JOSEPH-NATHAN,LUISA U. ROMAN*and JUAN D. HERNANDEZ* Departamento de Quimica de1Centro de Investigacibn y de Estudios Avanzados, Instituto Politknico National, Apartado 14-740, Mexico City, 07000Mkxico;*Institute de Investigaciones Quimico-Biolbgicas, Universidad Michoacana de San Nicolk de Hidalgo, Morelia, Mich., 58240 M&co (Received

Key Word Index-Steuia derivatives.

18 June 1992)

origanoides; Eupatorieae;

Compositae; roots; sesquiterpenes; longipinene

Abstract-The roots of Steoia origanoides afforded three new longipinene derivatives, their structures being established by spectroscopic methods and chemical transformations. The structure and stereochemistry of one of these compounds is further supported by single crystal X-ray analysis of a derivative.

INTRODUCTION In continuation of our chemical research on Steoia species from the Mexican flora [l-3], we have now studied the chemical constituents of the roots of Steuia origanoicfes HBK. We report the isolation and identification of three new longipinene derivatives: longipin-2-ene-71-acetyloxy-9a, 15-diangeloyloxy- 1-one (I), longipin-2-ene-7/?acetyloxy-15-angeloyloxy-l-one (2) and longipin-2-ene7/3-ace.tyloxy-9cr-senecioyloxy-15-angeloyloxy-l-one (3). Their structures were elucidated by examination of spectral data and the stereochemistry of 1 further follows from the single crystal X-ray diffraction analysis of diacetate 9.

It’ 1

Ii=

&Sk

It3 Ang

3 sell Ac 4 Ang Ang SAngH 6AngH

Ang Ang Aag H

RESULTSANDDISCUSSION From the hexane extracts of the roots of Steoia origanodes, the known triterpenes friedeline [4] and stigmasterol [S] were isolated together with the new natural longipinene derivatives l-3. Compound 1 was isolated as an oil. Its IR spectrum showed characteristic’absorptions for an acetate carbonyl group (1733 cn- ‘), an gfi-unsaturated ester group (1712 and 1648 cm- ‘) and an a&unsaturated ketone (1676 and 1619 cm-‘). The mass spectrum showed [M]’ at m/z 472, consistent with the molecular formula C,,H,,O,. The ‘H NMR spectrum showed an AB system at 64.06 (1H,d,J=11.3Hz)and3.79(1H,d,.J=11.3Hz)whichis assigned to the methylene group at C-15 where one of the esters is attached. The rest of the ‘H NMR and 13C NMR data are in agreement with structure 1, which is closely related to 4, a natural product obtained from S. potrerensis [6]. Comparison of the ‘HNMR spectrum of 1 (see Experimental) with spectra of known compounds [S-7] suggests that the angelate groups are at C-9 and C- 15 and the acetate group is at C-7. PHY32:5-J

R’ 8H 9 AC 10 Ac

7

-‘=q 5

R2 H Ac H

--* S

In order to corroborate the acetate position, compound 5 was prepared by controlled alkaline hydrolysis of 1. This chemical transformation allowed us to assign the acetate group at C-7, as deduced from its ‘H NMR 1219

C. M. CERDA-GARCIA-ROJASet al.

1220

spectrum since the double doublet corresponding to H-7 [S] was shifted from 65.37 to 4.07. The assignment of the proton signals of the methyl groups (H-13 and H-14) was done after converting 1 into acetonide 7 as follows. Alkaline hydrolysis of 1 afforded dio16 in almost quantitative yields. Treatment of 6 with acetone and p-toluenesulphonic acid gave acetonide 7, in which one of the methylene protons at C-15 shows a W coupling with the C-14 methyl protons. The methyl ‘H NMR assignment was verified by irradiation of the H-15 broad doublet at 63.70, thus causing sharpening of the broad singlet of H-14 at 5 1.14 and, therefore, the singlet at 6 1.01 was assigned to H-13. The i3C NMR assignments were confirmed from a 2D 13C/‘H chemical shifts correlation diagram. In order to corroborate the structure of 1 and to establish its stereochemistry, we prepared a derivative suitable for X-ray analysis. Thus, reduction of 7 with LiAlH, afforded diol 8, which was treated with acetic anhydride and pyridine to afford diacetate 9 and monoacetate 10. The diacetate 9 was obtained as a crystalline solid, mp 222 -224 /I. Its X-ray diffraction analysis provided the molecular perspective (Fig. 1) which showed the tl orientation of the methylene group at C-15. Since the absolute configuration of longipinenes from Steoia is known [9], the new chiral centre at C-6 is S, while the remaining chiral centres show the same configuration as in other longipinene derivatives [9]. Compound 2 was isolated as an oil. The IR spectrum showed absorption for an acetate carbonyl group (1731 cm-‘), an Q-unsaturated ester group (1712 and 1648 cm- ‘) and an a&unsaturated ketone (1671 and 1614 cm-‘). The mass spectrum showed [M]’ at m/z 374 consistent with the molecular formula C22H3005. The 1H NMR signals at 6 5.02 ( 1H, dd, J = 1.5 and 11 Hz) and the AB system at 64.00 (1H. d, J= 11.3 Hz) and 3.82 (lH, d, J = 11.3 Hz) suggest the presence of esters at C-7 and C15. Comparison of the ‘H and i3C NMR data of 1 and 2 (Table 1 and Experimental ) indicates the only difference

Fig.

1.

Molecular perspective of compound 9.

between the two compounds is the replacement of the angelate group of 1 by an hydrogen at C-9 of 2. This comparison also establishes that the acetate group is at C-7 and the angelate group is at C-15 in 2. The IR spectrum of 3 showed absorptions for an acetate carbonyl group (1733 cm-‘), an angeloyl group (1712 and 1651 cm-‘), a senecioyl group (1701 and 1653 cn-‘) and an Q-unsaturated ketone (1617 and 1672 cm- ‘). Comparison of the ‘H and i3C NMR spectral data (Table 1 and Experimental) with those of known compounds [7,8, lo] establishes that the acetate group is 78, the seneciate group is 9a and the angelate group is at c-15. EXPERIMENTAL

Mps: uncorr; UV: EtOH; IR: films; Specific rotations: CHCl,; ‘H and i3C NMR: in CDCl, with TMS as int. standard; EIMS:.70 eV; CC: Alcoa F-20 alumina (80-200 mesh) or silica gel 60 (70-230 mesh). Plant material. Steuia origanoides HBK was collected at Km 20 of the Morelia-Mexico highway (Via Mil Cumbres), in the state of Michoacan, Mexico, during October 1988. A voucher specimen is deposited at the herbarium of the Instituto de Ecologia, A. C., Patzcuaro, Mich. ,where Prof. Jerzy Rzedowsky identified the plant material. Extraction and isolation of compounds 1 and 2. Air-dried roots (1 kg) of Stevia origanoides were extracted with hexane and chromatographed by CC on alumina (80-200 mesh). Fractions eluted with hexane-CHzCl, (7: 3) yielded a mixture of longipinenes. They were further separated by CC on silica gel 60 (70-200 mesh). Fractions eluted with hexane-CHzClz (7: 3) yielded 1 (400 mg) as an oil. EIMS m/z (rel. int.): 472 [M]’ (0.6), 83 (64.1), 55 (40.3), 43 (100); UV E.EzH nm (log E): 227 (4.08), 253 (3.82); IR v;;;” cm’: 1733 (C=o, 1712, 1648 (O=C-C=C, angelate), 1676, Ac), a&unsaturated 1619 (O=C-C=C, ketone): 589 578 546 436 565 nm __ (CHCl,; ~0.3). Cal= +50 +52 +60 +119 +270 ‘HNMR (300 MHz): 66.14 (lH, qq, J= 7.5 and 1.5 Hz, H-3, angelate), 6.08 (lH, qq, J= 7.5 and 1.5 Hz, H-3, angelate), 5.80 (lH, qdd, J,,,=J,,,, =1.3 and Jz,,, = 1.5 Hz, H-2), 5.37 (lH, dd, J7,8,=2.2 and J,,,, = 11.7 Hz, H-7), 5.14 (lH, t, J=3.4 Hz, H-9), 4.06 (lH, d, J 15.15.=11.3H~,H-15).3.71 (lH,d,J,,,,,, ~11.3 Hz,H15’),3.35(1H,dd,J,,,,=1.3andJ,,,,=7Hz,H-11),2.68 (lH,dd,J,,,=1.3andJ,,,,=7Hz,H-4),2.55(lH,s,H-5) Hz, 2.27 (lH, ddd, J7,so = 11.7, Jso1,s8= 15 and J,,,,=3.4 H-8P), 2.14 (lH, ddd, J,,,,=2.2, J,,,sB=15 and JsaT9 =3.4 Hz, H-8a), 2.06 (3H, d, J2,12= 1.5 Hz, Me-12) 2.03 (3H, dq, J=7.5 and 1.5 Hz, Me-4 angelate), 2.02 (3H, s, OAc), 1.97 (3H, quin, J = 1.5 Hz, Me-5 angelate), 1.96 (3H, dq, J=7.5 and 1.5 Hz, Me-4 angelate), 1.92 (3H, quin, J = 1.5 Hz, Me-5 angelate), 1.05 (3H, s. Me-14) and 0.99 (3H, s, Me-13); 13C NMR (CDCI,); 6169.6,2l.O(acetate), 167.4, 139.2, 127.4, 20.6, 15.8 (angelate), 167.1, 139.1, 127.8, 20.5, 15.9 (angelate). For the sesquiterpenoid signals see Table 1.

1221

Longipinenes from Stevia origanoides Table 1. 13C NMR spectra1 data for longipinene derivatives (CDCI,, 75.4 MHz, TMS as int. standard)

C

1

2

3

5

6

1

8

9

10

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

202.2 122.9 169.8 48.4 62.3 40.6 67.7 32.0 74.4 55.8 54.6 23.3 21.3 14.6 69.2

203.3 122.6 170.2 49.0 61.9 40.6 73.0 37.1 26.7 54.6 58.4 23.4 24.2 15.5 69.2

202.5 122.9 169.8 48.4 62.2 40.7 67.9 32.1 73.1 55.9 54.3 23.3 21.3 14.7 69.2

202.7 122.8 170.1 48.3 62.9 41.9 64.8 35.0 74.8 55.9 54.5 23.3 21.3 13.5 70.8

203.6 122.7 171.3 48.1 61.7 41.6 71.9 35.2 74.9 56.4 54.1 23.4 21.4 13.2 69.1

202.8 122.8 170.5 48.4 60.2 36.4 68.2 33.8 74.5 56.1 54.1 23.4 21.6 14.1 69.4

74.1 120.8 148.2 46.4 55.1 35.3 67.9 36.6 14.9 45.7 42.3 22.5 22.7 14.4 69.9

75.5 117.5 150.1 45.9 55.0 35.3 68.2 33.8 76.6 45.5 40.8 22.4 21.9 14.2 69.8

75.7 117.5 150.5 46.3 55.4 35.4 67.7 36.8 74.8 46.2 40.1 22.5 22.5 14.3 69.9

The shifts due to ester residues are given in the Experimental.

The fractions eluted with hexane-CH,Cl, (1: 1) yielded 5 mg 2 as an oil. EIMS m/z (rel. int.): 374 [M] + (0.4), 83 (53.9), 55 (37.7), 43 (100); UV iFzH nm (log E): 220 (4.05), 255 (3.90); IR v::;‘~ cm-‘: 1731 (C=O, OAc), 1712, 1648 (O=C-C=C, angelate), 1671, a&unsaturated ketone); 1614 (O=C-C=C, 586 578 546 436 365nm (CHCl,; c 0.2). Cal= +9 +lO +ll +23 +57 ‘H NMR (300 MHz): 66.06 (lH, qq, J=7.5 and 1.5 Hz, H-3 angelate), 5.76 (lH, em,J= 1.3 and 1.5 Hz, H-2), 5.02 (lH, dd, J,,,,=1.5 and J,,,,=ll Hz, H-7), 4.00 (lH, d, J 15,15,= 11.3 Hz, H-15), 3.82 (lH, d, J15,15,= 11.3 Hz, H153, 2.94 (lH, dd, J,,,,=1.3 and J,,,,=6.6Hz, H-11), 2.68 (lH, d, J,,, 1= 6.6Hz, H-4), 2.44 (lH, s, H-5), 2.07 (3H, s, Me OAc), 2.04 (3H, d, J2,12 = 1.5 Hz, Me-12), 1.96 (3H, dq, J=7.5 and 1.5 Hz, Me-4 angelate), 1.91(3H, dq, J = 1.5 Hz, Me-5 angelate), 1.05 (3H, s, Me-14), 0.97 (3H, s, Me-13). The signals of H-8cr and H-8b were overlapped in the 61.8-2.1 region. “CNMR (CDCI,): 6171.2, 21.2 (acetate), 167.4, 139.0, 127.5,20.8, 15.8 (angelate). For the sesquiterpenoid signals see Table 1. Isolation of compound 3. Air-dried roots (3 kg) of S. origanoides collected at the same location in October 1990 were extracted with hexane and chromatographed on CC with alumina. The first fractions eluted with hexane-EtOAc (19 : 1) were rechromatographed by CC on silica gel. The fractions eluted with hexane-EtOAc (9: 1) yielded 5 mg 3 as an oil. UV 1::” nm (log e): 224 (4.17), 250 (3.77); IR vg:‘I cm-‘: 1712, 1651 (O=C-C=C, 1733 (C=O, OAc), angelate), 1701, 1653 (O=C-C=C, seneciate), 1672, ketone); a&unsaturated 1617 (O=C-c=c, 58s 578 546 436. 365 nm (CHCI,; c 0.05). Cal= +14

+19

+23

+33

+58

‘H NMR (3&l MHz): 66.10 (lH, qq, J=7.5 and 1.5 Hz, H-3 angelate), 5.79 (lH, m, J = 1.5 Hz, H-2), 5.73 (lH, qq, J =l Hz, H-2 seneciate), 5.37 (lH, dd, J,,s,=2.1 and J,,eS = 11.7 Hz, H-7), 5.06 (lH, t, J=3.4 Hz, H-9), 4.01 (lH, d,

J 1S,15’= 11.3 Hz, H-15), 3.83 (lH, d, J15,ist= 11.3 Hz, HW), 3.33 (lH, d, J,,,,= 6 Hz, H-11), 2.65 (lH, d, J,,,,

=6Hz,H-4),2.55(1H,s,H-5),2.18(3H,d,J=lHz,Me-4 seneciate), 2.06 (3H, d, J2,12 = 1.5 Hz, Me-12), 2.02 (3H, s, Me OAc), 1.98 (3H, dq, J = 7.5 and 1.5 Hz, Me-4 angelate), 1.95 (3H, quin, J= 1.5 Hz, Me-5 angelate), 1.92 (3H, d, J = 1 Hz, Me-5 seneciate), 1.05 (3H, s, Me-14), 0.98 (3H, s, Me-13); “C NMR (CDCl,k 6169.8, 21.1 (acetate), 167.6, 139.0, 127.5,20.7, 15.8 (angelate), 166.0, 157.7, 115.9,27.6, 20.5 (seneciate). For the sesquiterpenoid signals see Table 1. Partial alkaline hydrolysis of compound 1.To a soln of 1 (100 mg) in cold MeOH (16 ml) was added KOH (100 mg) in H,O (4 ml) and the mixture was stirred for 1 hr at room temp. The reaction mixture was extracted with EtOAc. The organic layer was washed with H,O, dried over Na,SO,, filtered and evaporated to dryness. The residue was chromatographed on silica gel. The fractions eluted with CH,Cl,-Me&O (9: 1) gave 40 mg longipin2-ene-7/&hydroxy-9a,15-diangeloyloxy-l-one (5) as [M]+ EIMS m/z (rel. ’ . : 430 oil. (ao?7), 83 (63.4), 55 (lOO), 43 ‘$8); UV n:EH nm (log e): 223 (4.24), 250 (3.93); IR ~~2:‘~ cm-‘: 3509 (OH), 1710, 1647 (O=C-C=C, angelate), 1676, 1617 (O=C-C=C, a&unsaturated ketone); 589 5?8 546 436 365 nm (CHCl,; c 0.4). Cal= +68 +72 +82 +166 +475 ‘HNMR(300 MHz):66.16(1H,qq, J=7.5 and 1.5 Hz, H-3 angelate), 6.11 (lH, qq, J=7.5 and 1.5 Hz, H-3 angelate), 5.78 (lH, m, J= 1.2 and 1.5 Hz, H-2), 5.18 (lH, t, J=3.4 Hz, H-9), 4.45 (lH, d, 5,,,,,.=11.3 Hz, H-15)4.06(1H,dd,J,,,,=1.7andJ,,s8=12.2 Hz,H-7), 3.72 (lH, d, J,s,15,= 11.3 Hz H-15’), 3.16 (lH, dd, J,,,, =1.2 and J4,il= 6.8 Hz, H-11), 2.65 (lH, d, J4,11 =6.8 Hz, H-4), 2.53 (lH, s, H-5), 2.33 (lH, ddd, J,,,, =12.2, JBti,BB= 15 and J,,,,=3.4 Hz, H-8fi), 2.09 (lH, ddd, J,,s.=1.7, J,,,,,=15 and J,,,,=3.4 Hz, H-8@), 1.5 Hz, Me-12), 1.99 (3H, dq, J=7.5 2.06 (3H, d, J,,,,=

C. M. CERDA-GARCIA-ROJAS et d.

1222

and 1.5 Hz, Me-4 angelate), 1.98 (3H, dq, J= 7.5 and 1.5 Hz, Me-4 angelate), 1.92 (3H, quin, J = 1.5 Hz, Me-5 angelate), 1.88 (3H, dq, J = 1.5 Hz, Me-5 angelate), 0.98 (3H, s, Me-14), 0.96 (3H, s, Me-13); 13C NMR (CDCI,); 6168.2, 140.5, 127.7, 20.7, 15.9 (angelate), 166.9, 139.1, 127.0, 20.9, 16.0 (angelate). For the sesquiterpenoid signals see Table 1. Alkaline hydrolysis ofc~rn~~~nd 1. To a soln of l(1 g) in MeOH (32 ml) was added KOH (1 g) in H,O (8 ml) and the mixture was stirred for 1.5 hr at room temp, The reaction mixture was extracted with EtOAc. The organic layer was washed with H,O, dried over Na,SO,, filtered and evapd to dryness. The residue was chromatographed on silica gel. The fractions eluted with CH&l, Me&O (4 : 1) gave 580 mg longipin-2-ene-7/Ghydroxy-9?angeloyloxy-15hydroxy-l-one (6) as an oil. EIMS m/z (rel. int.): 348 [M]’ (0.4), 330 (O.l), 83 (loo), 55 (29.4), 43 (16.0); UV AEgHnm (log E):225 (3.89) 250 (3.79); IR v~~~‘~ cm-‘: 3430 (OH), 1710, 1652 (O=C-C=C, angelate), 1671, 1617 (O=C-C==C, @-unsaturated ketone); 365 nm (CI-ICI,; c 0.5). =495 ‘H NMR (300 MHz): 66.12 (lH, qq, J=7.5 and 1.5 Hz,

tu1=

589

578

-1-61 +I+75

546

436

+157

H-3 angelate), 5.77 (lH, m, J= 1.5 Hz., H-2), 5.17 (lH, f, J =3.4Hz, H-9), 4.22 (lH, dd, Ji,sa=1.6 and J,,aa = 11.9 Hz, H-7), 3.64 (lH, d, Ji5,i5/= 10 Hz, H-15), 3.35 (lH, d, Jis,i5)= 10 Hz, H-15’), 3.09 (lH, dd, Jz,l, = 1.5 and J4,, , = 6.8 Hz, H-11), 2.68 (lH, d, J,,l, =6.8 Hz, H4), 2.27 (lH, ddd, J,.s8=11.7, JS..s8=15.2 and J,,, ~3.4 Hz, H-8/?), 2.17 (lH, s, H-5), 2.06 (3H, d, J,,,z = 1.5 Hz, Me-12), 2.05 (3H, dq, J-7.5 and 1.5 Hz, Me-4 angelate), 1.99 (lH, ddd, J7,8.= 1.6, JsaaS8= 15.2 and Js.,9 =3.4 Hz, H-8@, 1.92 (3H, quin, J= 1.5 Hz, Me-5 angelate), 1.05 (3H, s, Me-14), 0.97 (3H, s, Me-13); i3C NMR (CDCI,); 6 167.0,138.7,127.7,20.7,16.0(ange1ate). For the sesquiterpenoid signals see Tabfe 1. Acetonide 7. A soln of 6 (100 mg) and p-toluenesulphonic acid (10 mg) in C,H, (30 ml) and Me&O (1 ml) was refluxed for 2 hr. The reaction mixture was extracted with EtOAc. The organic layer was washed with NaHCO, (satd soln) and HZO, dried over Na,SO,, filtered and evapd to dryness. The residue was chromatographed on silica gel. The fractions eluted with hexane-EtOAc (4 : 1) gave 102 mg long~~in-2-ene~?~hydroxy-9a-angeloyloxy-15-hydroxy-l-one 7,15-acetonide (7) as an oil. EIMS m/z (rel. int.): 388 [M] + (0.5), 83 (1 00), 55 (48.4) 43 (24.2); IJV lgEH nm (log E):225 (3.92), 250 (3.84); IR $~~i3 cm -l: 1712, 1648 (O=C-C=C, angelate), 1676, 1618 (0 = C-C = C, Q-unsaturated ke589 578 546 436 365 nm (CHCI,; tone); [a] = f50 +52 +60 l-129 -t-427 c O.~).‘HNMR~~~MHZ): 66.12 (lH, qq, J=7.5 and 1.5 Hz, H-3 angelate), 5.81 (lH, 111,J= 1.2 and 1.5 Hz, H2), 5.22 (lH, t, J=3.3 Hz, H-9), 4.22 (IH, dd, J7,8a= 1.2 and J,,,p= tl.9Hz,H-7),3.70(1H,d,J,,,1s~=11 Hz,H15),3.17(lH,d,J,,~,~~=ll H~,H-l5’),3.18(1H,dd,J,,~~ =1.2andJ,,,= 7Hz,H-ll),2.68(lH,d,J4,11=7H~,H4), 2.20 (lH, ddd, J,,,,=l1.9, JBa,sB=15 and J,,, =3.3 Hz, H-8fl), 2.06 (3H, d, JZ,iZ=1.5 Hz, Me-12), 2.05 (lH, s, H-5), 2.02 (3H, dq, J=7.5 and 1.5Hz, Me-4

angelate), 1.92 (3H, dy, J = 1.5 Hz, Me-5 angelate), 1.85 (lH,ddd, J7,8.=1.2rJ8;r.88=15andJ,,,=3.3Hz,H-8a),

1.43 (6H, s, acetonide gem-dimethyl), 1.14 (3H, s, Me-14), 1.01 (3H, s, Me-13); i3C NMR (CDCI,) 5 166.8, 138.7, 127.7,20.7,16.0(angelate),99.2,29.6,19.0(acetonide). For ~squiterpenoid signals see Table 1. Reduction of acetonide 7. A soln of 7 (100 mg) in tetrahydrofuran (10 ml) was treated with LiAlH, (200 mg) and refluxed for 2 hr. The reaction mixture was treated with 30 ml EtOAc and 10 ml H,O and stirred at room temp. during 30 min. After filtration. the organic layer was sepd, washed with H,O, dried over Na,SO,, filtered and evapd to dryness. This yielded 39 mg longipin-2-ene-ljI,7~.9a-15-tetrahydroxy 7,15-acetonide (8). IR vz;;13 cm - 1: 3448 (OH), 1067 (C-O); 589 578 546 436 365 nm (CHCI,; c 0.2). ‘“‘=~15+1 + 18 +29 +44 ‘HNMR (300 MHz): 65.41 (lH, m, H-2), 4.48 (lH, m, H1),4.27(1H,dd,J,~s,=l.5 andJ~,sB=11.8Hz,H-7), 3.90 (lH, t, J=3.2 Hz, H-9), 3.64(1H, d,J,,,,,,=lL7Hz, H15), 3.11 (lH, d, J,5,tS+= 11.7 Hz, H-15’). 2.77 (lH, m, Hll), 2.15 (lH, d, J4.11= 6.6 Hz, H-4), 2.09 (lH, ddd, J7,88 = 11.8, Jsn,s8= 15 and J,,,,=3.2 Hz, H-S/I), 1.76 (3H, t, Me-12), 1.73 (lH, ddd, J,,,,=l.5, J,,,,#=15 and Jsa,9 = 3.2 Hz, H-&Q, 1.48 (3H, s, acetonide methyl), 1.44 ( 3H, s, acetonide methyl), 1.31 (lH, s, H-5), 1.24(3H,s, Me-13), 1.04 (3H, s, Me-14), i3CNMR (CDCI,); 599.11, 29.71, 19.35 (acetonide). For the sesquiterpenoid signals see Table 1. Acetylation of compound 8. A soln of 8 (50 mg) in pyridine (2 ml) was treated with Ac,O (1 ml) and stored at room temp. for 6 hr. The reaction mixture was extracted with EtOAc. The organic layer was washed with HCl (10%) and H,O, dried over Na,SO,, filtered and evapd to dryness. The residue, a mixture of acetates 9 and 10,was chromatographed on silica gel. The fractions eiuted with hexane--EtOAc (4: 1) gave 32 mg of the diacetate 9 as crystals which were recrystallized from CHCl,-hexane, mp 221-224”. IR $,~~I3 cm- ‘: 1723 (C=O, OAc), 1062 589 578 546 436 365nm (CHCl,; (‘-O); [‘I = -16-11 _~~-3~~-“c 0.3). ‘H NMR (300 MHz): 65.47 (19 m, H-l), 5.38 (lH, m, H-2), 5.10 (lH, 1, J=3.3 Hz, H-9), 4.13 (lH, dd, J,,*. =I.3 and J7,88= 12Hz, H-7), 3.67 (lH, d, J15,,5. = 10.7 Hz, H-15) 3.14 (lH, d, J15_15’= 10.7 Hz, H-15’), 2.86 (lH, m, H-11), 2.22 (lH, d, J4,11 ~6.4 Hz, H-4), 2.09 (3H, s, OAc), 2.07 (lH, ddd, J,,88= 12, 3,,,,@=15 and J sbr,9=3.3 Hz, H-8/?), 2.04 (3H, s, OAc), 1.77 (3H, t, Me12), 1.75 (lH, ddd, J,,a,=1.3, JSa,BB= 15 and Jso.o = 3.3 Hz, H&x), 1.46 (3H, s, acetonide methyl), 1.43 ( lH, s, H-5) 1.42 (3H, s, acetonide methyl), 1.05 (3H, s, Me-14), 1.02 (3H, s, Me-13); 13C NMR (CDCI,) 6170.7, 21.3 (acetate), 170.3, 21.3 (acetate), 99.1, 29.6, 19.2 (acetonide). For the sesquiterpenoid signals see Table 1. The fractions eluted with hexane-EtOAc (1: 1) gave 12 mg of acetate 10 as an oil. IR v~~ir cm-‘: 3471 (OH), 1725 fC=O, OAc), 1062 (C-O); 589 578 546 436 365 nm Cal= (CHCI,; c 0.1). -17 -19 -23 -52 -91 ‘H NMR (300 MHz): 65.46 (lH, m, H-l), 5.38 (lH, m,

1223

Longipinenes from Steuia origanoides

H-2), 4.24 (lH, dd, J,,8a= 1.5 and J7,88= 12 Hz, H-7),3.91 (lH, t, J=3.4Hz,H-9), 3.67(1H,d, J,,,,,.=10.6Hz, H15), 3.12 (lH, d, J15,15,= 10.6 Hz, H-15’), 2.80 (lH, m, Hll), 2.17 (lH, d, J,,,,= 6Hz, H-4), 2.10 (lH, ddd, J7,88 =12, Js,,,=lS and Js,,,=3.4Hz, H-Sa), 2.04 (3H, s, OAc), 1.77 (3H, t, Me-12), 1.71 (lH, ddd, J7.s.= 1.5, Jez,sS =15 and JB.,9 =3.4 Hz, H-8a), 1.47 (3H, s, acetonide methyl), 1.43 ( 3H, s, acetonide methyl), 1.40 (lH, s, H-5), 1.18 (3H, s, Me-13), 1.05 (3H, s, Me-14); 13CNMR (CDCl,) 6 170.8,21.4 (acetate), 99.1,29.7,19.3 (acetonide). For the sesquiterpenoid signals see Table 1. X-Ray analysis of compound 9. Single crystals of 9 were grown by slow crystallization from CHCl,-hexane. They were orthorhombic, space group P2r2,2, with a = 8.854(4), b = 14.547(6), c = 17.033(9) A and dcsle= 1.19 g crn3 for Z=4 (M, 392). The size of the crystal used for data collection was 0.04x0.16x 0.35 mm. No absorption correction was necessary (p = 6.59 cm- ‘). A total of 1633 reflections were measured for 3 ’ < 06 110 ’ of which 1210 were considered to be observed. The final discrepancy indices were R=5.06% using 1043 reflections in the final refinement. The final difference Fourier map was essentially featureless, the highest residual peaks having densities of 0.2 Am3. Lists containing atomic coordinates and thermal parameters, bond distances, bond angles, anisotropic temperature factors, hydrogen atom coordinates and comparison of the observed and calculated structure factors have been deposited at the Cambridge Crystallographic Data Centre.

REFERENCES

1. Roman, L. U., de1 Rio, R. E., Hernandez, J. D., Joseph-Nathan, P., Zabel, V. and Watson, W. H. (1981) Tetrahedron 37, 2769. 2. Roman, L. U., Hemandez, J. D., Castafieda, R., Cerda, C. M. and Joseph-Nathan, P. (1989) Phytochemistry 28, 265.

Roman, L. U., Hernandez, J. D., Cerda, C. M. and Joseph-Nathan, P. (1991) Phytochemical Anal. 2, 77. Patra, A. and Chaudhuri, S. K. (1987) Magn. Reson. Chem. 25,95.

Wright, J. L. C., MacInnes, A. G., Shimizu, S., Smith, G. D., Walter, J. A., Idler, D. and Khalil, W. (1978) Can. J. Chem. 56, 1898. Gil, R. R., Oberti, J. C., Sosa, V. E. and Herz, W. (1987) Phytochemistry 26, 1459. Bohlmann, F., Suwita, A., Natu, A. A., Czerson, H. and Suwita, A. (1977) Chem. Ber. 110, 3572. Roman, L. U., de1 Rio, R. E., Hernandez, J. D., Cerda, C. M., Cervantes, D., Castafieda, R. and JosephNathan, P. (1985) J. Org. Chem. 50, 3965. 9. Joseph-Nathan, P. Cerda, C. M., de1 Rio, R. E., RomBn, L. U. and Hernandez, J. D. (1986) J. Nat. Prod. 49, 1053.

10. Roman, L. U., Hernandez, J. D., Cerda, C. M. and Joseph-Nathan, P. (1989) J. Nat. Prod. 52,481.