Phytochemutry, Vol. 32, No. 3, pp. 741 745, 1993 0031-9422/93 $6.00+0.00 Printed in Great Britain. Q 1993 Pergamon Press Ltd

SINAPIC ACID ESTERS FROM POLYGALA F’IRGATA

AHMAD BASHIR, MATTHIAS HAMBURGER, JEROME D. MSONTHI*~ and KURT HOSTETTMANN~

Institut de Pharmacognosie et Phytochimie, Cole de Pharmacie, Universitk de Lausanne, BEP, CH-1015 Lausanne, Switzerland; *Department of Chemistry, Chancellor College, University of Malawi, Zomba, Malawi

(Received 1 June 1991)

IN HONOUR OF PROFESSOR MEINHART ZENK’S SIXTIETH BIRTHDAY

Key Word Index-Polygala uirgata; Polygalaceae; sinapic acid esters; sucrose esters; ‘H and 13C NMR; selective INEPT.

Abstract-Three sinapoyl glycosides have been isolated from the roots of Polygala uirgata. The structures were established on the basis of UV, mass, ‘H and 13C NMR spectral data, including homonuclear and heteronuclear 2D shift correlation and selective INEPT experiments. cc-D-(3-0-Sinapoyl)fructofuranosyl-cr-D_tyl-6-o-sina- poyl)glucopyranoside and ~-D-(3-O-sinapoyl)fructofuranosyl-cc-D-(yl)glucopyranoside are new natural products, whereas B-D-(3-O-sinapoyl)fructofuranosyl-cr-D-(6-O-sinapoyl)~ucopyranoside has already been reported from other plants.

INTRODUCTION

In continuation of our investigations on African and American Polygalaceae species [l, 21, we have studied Polygala uirgata. It is a herb or small shrub up to 1.5 m tall, which is particularly found in South Africa and on high plateaux of Malawi. Previous studies on the seed oil composition of P. virgata have shown the presence of acetylated triglycerides [3], but there has been no report on the secondary metabolites of this species prior to our own work. A first investigation of the lipophilic root extract afforded a series of isoflavones and xanthones [4]. Further analysis of the dichloromethane and methanolic extracts of the roots by TLC and LC-UV revealed the presence of hydroxycinnamic acid derivatives. We report here on the isolation and structure elucidation of three sinapoyl esters of sucrose.

RESULTS AND DISCUSSION

The dried roots were successively extracted with di- chloromethane and methanol. The methanol extract was first partitioned between n-butanol and water. Further separation of the butanol extract by flash chromato- graphy on silica gel and gel filtration on Sephadex LH-20 afforded 1 and 2. CC of the dichloromethane extract on silica gel, followed by gel filtration on Sephadex LH-20 (MeOH-CH,Cl,, 1: 1) and LPLC on a Diol column led to the isolation of 3.

tPresent address: Chemistry Department, University of Swaziland, Kwaluseni, Swaziland.

$Author to whom correspondence should be addressed.

OH

OCHs

0

R’ I32

1 H H

2 AC H

3 H AC

Upon acidic hydrolysis of l-3 with 2N HCl, the aglycone decomposed. However, glucose and fructose were tentatively identified by co-TLC with authentic samples. Basic hydrolysis of l-3 with 0.5N NaOH afforded sinapic acid. A disaccharide, identical to sucrose with regard to chromatographic behaviour and staining, was found in all three cases. D/CIMS of 1 showed a quasimolecular ion at m/z 772 [M + NH,] +. The frag- ment ion at m/z 566 [M + NH4-2061 + and 360 [M + NH, - 412]+ were indicative of two sinapoyl moieties, whereas the signals at m/z 404 [M + NH4 - 162 - 206]+ and

PHY 32:3-q 741

742 A. BASHIR et al.

386 [M + NH, - 180 - 206]+ resulted from a symmetri- cal cleavage of the molecule at the interglycosidic linkage. Absence of fragment ions at m/z 610 [M + NH, - 162)’ and 592 [M + NH, - 1 X0]‘, which would correspond to the elimination of a hexose residue, suggested esterifica- tion of one sinapoyl group on each of the two hexosyl units. Indeed, strong [M+NH,- 180]+ and [M+NH, - 162]+ fragment ions have been observed in the D/CIMS of 1,3-diesters of sucrose [5]. The positions ofesterification were determined by the detailed analysis of ‘H and 13CNMR spectra including selective INEPT experi- ments. Assignments of proton and carbon signals were based on homonuclear [double quantum filtered phase sensitive (DQPS) COSY] and heteronuclear (XHCORD) shift correlation spectra. The ‘HNMR spectrum of 1 revealed signals of two sinapoyl moieties [four aromatic methoxyls at 63.74 and 3.77 (6H each, s), a singlet equivalent to four aromatic protons at 6 6.94, and olefinic protons at 67.58,7.52,6.46 and 6.42 attributable to two E co,nfigurated double bonds]. Coupling constants and chemical shifts of the remaining signals were in accord with data reported for sucrose [6], with the exception of H-3, H,-6’ and H,-6’. The fact that they appeared at significantly lower field (0.5-1.5 ppm) suggested acylation at C-3 and C-6’. This was confirmed through a series of selective INEPT experiments [7]. Polarization transfer from the signal at 66.44 (H-8” and H-8”‘) enhanced the

carbonyl carbons at 6 166.1 and 167.3, and the signals of quaternary carbons at 6 124.9 and 125.0 (C-l” and C-l”‘). Long range correlation of H-3 (a 5.37) with C-2 (6 103.5) and C-9” (6 166.1) confirmed the attachment of a sinapoyl group at C-3 of the fructofuranosyl moiety. On the other hand, a three bond correlation between H,-6’ (64.68, CD,OD) and C-9”’ (6 169.0, CD,OD) proved the second sinapoyl group to be esterified to C-6 of the glucosyl residue. Thus, the structure of 1 was established as p-D-(3-

O-sinapoyl)fructofuranosyl-a-o-(6-O-sinapoyl)glucopyr- anoside, a known constituent of Polygala tenu!folia (Poly- galaceae) [8] and ~a~~a~~s saticus (Brassicaceaef [93.

The negative ion FABMS of 2 exhibited a quasimole- cular ion at m/z 795 [M -H] _. The fragment ion at m/z 589 [M -H - 2063~ indicated the loss of a sinapoyl group. ‘H and “CNMR data (Tables 1 and 2) confirmed the presence of one acetyl and two sinapoyl groups. *H NMR signals of the sugar moiety were assigned with a DQPS COSY spectrum. Signals attributable to the sinapoyl residues and the sucrose moiety were identical with those of 1, with the exception of H-Z’, H-3‘ and H-4’. A significant downfield shift of 1.5 ppm in the signal of H-3’ together with the slight deshielding of H-2’ and H-4’ ( + 0.2 ppm) indicated that the third acyl group was linked to C-3‘. The positions of the sinapoyl and acetyl groups

were subsequently confirmed with the aid of selective INEPT experiments. Long range polarization transfer

Table 1. ‘H NMR (200 MHz, DMSO-$) data of 1-3

H Sucrose* 1 2 3

H,-1

H,l

3

4

5

H,-6

H,-6

1’ 2

3

4

5

H,-6’

H,6’ 2”, 2”’ 6”, 6” 7”, 7”’

8”, 8”’

MeO-3”, MeO-3”’

MeO-5”, MeO-5”’

MeCOO

3.39 s

3.90 3.75 t (7.1) 3.57-3.63 unres.

3.54 s

3.15 d (3.7)

3.20 dd (9.5, 3.7) 3.47 t (9.5) 3.12 t (9.5) 3.56-3.63 unres.

3.54 s

3.38 s 3.39 s 3.44 s

5.37 d (8.0) 4.25 t (8.0) 3.77-3.86 unres.

5.40 d (8.0) 4.24 t (8.0) 3.71-3.82 unres.

3.58-3.67 unres. 3.65 unres.

5.37 d (7.5)

4.24 t (7.5)

3.60-3.81 unres.

3.60-3.81 unres.

5.30 d (3.6) 3.30 dd (9.0, 3.6) 3.46 t (9.0) 3.15 t (9.0) 4.08 d (9.0) 4.49 d (9.8)

5.38 d (3.6) 3.50 dd

(9.8, 3.6)

5.05 r (9.8)

3.36-3.38 unres.

4.10-4.18 mm.

4.48 d (10.1)

5.36 d (2.9) 3.40 dd (9.5, 2.9) 3.55 t (9.5) 4.63 t (9.5) 4.10-4.2s unres.

4.10-4.25 unres.

4.08 d (9.8)

6.92 s

4.10.-4.18 unres.

6.91 s, 6.89 s

7.56 d, 7.50 d (16.0)

6.44 d, 6.41 d (16.0)

3.73 s, 3.74 s

6.97 s

7.58 d, 7.52 d (16.0) 6.46 d, 6.42 d (16.0)

3 74 s, 3.77 s

7.59 d, 7.56 d ( 16.0) 6.50 d, 6.46 d (16.0)

3.78 s, 3.81 s

1.97 s 1.82 s

*Measured in DMSO-I, +D,0(85:15). In parentheses coupling constant (.I) values m Hz.

Sinapic acid esters from Polygala virgata 143

Table 2. r3CNMR (50.3 MHz, DMSO-d,) data of l-3

C Sucrose* 1 2 3

2 3 4 5’ 6 1” 1”’ 2,: 2”’

3”, 3”’ 4’, 4” 5”, 5”’ 6” 6”’ 7”’ 7”’ 8U: 8”’

9” 9”’

MeO-3”, MeO-3”’

MeO-5”, MeO-5”’ MeCOO- MeCOO-

62.2” 104.1

71.2 74.5 82.4 60.7 92.1 71.6 73.0b 69.9 72.gb 62.3

64.1 64.0 63.2 103.5 103.6 103.9

11.7 77.7 71.9 72.9 72.9 73.0 83.1 83.1 83.5 62.5 62.5 62.1 91.3 91.2 91.2 71.6 69.7 71.3 13.4 75.8 70.6 70.5 68.4 71.4 71.1 71.2 68.4 64.7 64.5 63.9

124.9, 125.0 125.1, 125.1 124.7, 124.7 106.5, 106.5 106.6, 106.6 106.5, 106.6 148.4, 148.4 148.5, 148.5 148.3, 148.4 138.5, 138.6 138.6, 138.6 138.8, 138.8 148.4, 148.4 148.5, 148.5 148.3, 148.4 106.5, 106.5 106.6, 106.6 106.5, 106.6 145.8, 146.3 146.1, 146.4 146.0, 146.1 115.1, 115.2 115.3, 115.3 114.8, 114.8

166.1 166.4 165.8 167.3 167.4 166.9

56.5 56.6, 56.7 56.4, 56.5

171.0 170.1 21.4 20.5

a.bAssignments interchangeable. *Measured in DMSO-d,+DIO (8515).

from H-3’ (65.05) and the methyl signal at 61.97 to the

a&y1 carbonyl(6 171.0) proved that the acetyl group was attached to C-3’. The positions of the two sinapoyl moie- ties were established as for sucrose diester 1. Compound 2 was, therefore, fl-D-(3-O-Sinapoyl)frUctOfUranOSyl-a-D-(3- 0-acetyl-6-0-sinapoyl)glucopyranoside, a new natural product.

The negative ion FABMS of 3 showed a quasimolecu- lar ion at m/z 795 [M -HI-. DjCIMS revealed a quasi- molecular ion at m/z 814 [M + NH,] +. The elimination of acetyl and sinapoyl moieties was indicated by fragment ions at m/z 772 [M + NH, - 42]+ and 608 [M + NH, -206]+. The ion peaks appearing at m/z 898 [M +NH, +84]+, 856 [M+NH4+42]+, and 650 [M+NH,+42 -206]+ were artefacts, due to the migration of acetyl groups during the desorption process. This phenomenon has already been observed for analogous structures [S]. ‘H and ‘%NMR data (Tables 1 and 2) confirmed the presence of an acetyl and of two sinapoyl groups. Hence, 3 was a positional isomer of triester 2. Comparison of the ‘H NMR data of 3 with those of 1 revealed that the signal of H-4’ was shifted downfield by 1.48 ppm and appeared at 64.63, indicating the attachment of the third acyl group

at C-4’. In a series of selective INEPT experiments (CDSOD), two and three bonds correlation between H-4 (64.74), methyl protons (61.97) and the acetyl carbonyl (6 172.1) confirmed that the acetyl group was esterified to C-4’. Based on ‘H and ‘%NMR spectral data (see Tables 1 and 2), the two sinapoyl moieties were attached to O-C-3 and O-C-6’. Thus, 3 could be characterized as 8-D-(3-O-SinapOyl)frUCtOfUranOSyl-a-D-(40- sinapoyl)glucopyranoside, a new natural compound.

Three sucrose esters (l-3) have been isolated from the roots of P. virgata. Analogous sucrose derivatives, such as mono-, di- and triesters with ferulic, sinapic or coumaric acid and mixed esters of ferulic and acetic acid have been reported from species of the Liliaceae [lO-143, Poly- gonaceae [15], Brassicaceae [9] and Polygalaceae [8, 161. Tetra and pentasaccharide polyesters have recently been reported from Polygala amarella and P. tenuifolia [17, 181. To our knowledge, 2 and 3 are the first mixed esters of sinapic and acetic acid.,

EXPERIMENTAL

General. MPs: uncorr. TLC was carried out on silica gel pre-coated Al sheets (Merck) and Diol HPTLC plates

744 A. BASHIR et al.

(Merck). The following solvent systems were employed: CHCl,-MeOH (9 : 1) (Diol), CHCl,-MeOH-HZ0 (70 : 30 : 5) (silica gel) and EtOAc-MeOH-H,O

( 100 : 14 : 7) (silica gel). For open CC, silica gel (40-63 urn, Merck) was used. UV spectra were recorded with addi- tion of usual shift reagents. Analyt. HPLC was performed on a Hewlett-Packard 1090 series II instrument equipped with a photodiode array detector. Purity of compounds was checked on Nucleosil RP-18 columns (7 urn, 250mm x4.6, i.d., Macherey-Nagel) at a tlow rate of 1.5 mlmin-‘. LPLC was carried out on a pre-packed Lobar column (LiChroprep, Dial, 40-63 pm, Merck) at a flow rate of 2 ml min- ‘. MS were recorded on a Finnigan MAT TSQ 700 triple stage quadrupole instrument. D/CIMS: positive ion mode, NH, as reactant gas. FABMS: negative ion mode, glycerol as matrix. ‘H and 13CNMR spectra were measured at 200 MHz and 50.3 MHz, respectively. TMS was used as an int. stand- ard. For double quantum filtered phase sensitive COSY experiments, 16 transients were recorded for each of the 2 x 256 increments. The final data matrix was 1K x 1K data points. Selective INEPT experiments [7] were per- formed in DMSO-d, or CD,OD, with delays optimized for “J, =4 or 8 Hz. The XHCORD spectra of 1 were recorded with 512 transients for each of 64 increments, and 1K data points in F,. The final data matrix was 128 x 1K data points.

Plant material. See ref. [4]. Extraction and isolation. Dried and ground roots of P.

uirgata (74 g) were successively extracted at room temp. with CH,Cl, and MeOH. The CH,Cl, extract (1.4 g) was fractionated by CC on silica gel (4.5 x 60 cm) into 9 frs (l-9) using step gradient elution (CHCl,-MeOH, 97:3-+4: 1, followed by MeOH). Further sepn of fr. 8 (250 mg) on Sephadex LH-20 (CH,Cl,-MeOH, 1: 1) yielded 3 frs (A-C). Compound 3 (66 mg) was obtained from fr. B (215 mg) by LPLC [Diol, n-hexane- CHCl,-MeOH (20: 74: 6)]. The methanolic extract (20.5 g) was dissolved in H,O and extracted with n-BuOH (3 x 500 ml). The butanolic extract (6.5 g) was submitted to flash chromatography on silica gel using step gradient elution (CHCl,- MeOH-H,O, 80:20:2-+60:40: 10). Fifteen frs (1-15) were constituted. Fr. 2 (154 mg) was purified by CC on Sephadex LH-20 to afford 2 (90 mg). The sepn of fr. 7 (700 mg) by gel filtration on Sephadex LH-20 (MeOH) yielded 3 fractions (A-C). Fr. B (355 mg) was subjected to CC on silica gel (EtOAc-MeOH-H,O, 100: 10:5), and 4 frs were collec- ted (I-IV). The purification of fr. II (205 mg) by CC on Sephadex LH-20 (MeOH) afforded compound 1 (165 mg).

Basic hydrolysis of compounds 1-3. Each compound (2 mg) was stirred with 0.5 N NaOH (5 ml) at room temp. for 24 hr. The reaction mixt. was adjusted to pH 6 with dil. HCI. The aglycone was extracted with Et,0 and co- chromatographed with an authentic sample of sinapic acid (silica gel, C,H,-dioxane-MeOH-HCO,H, 90: 25: 5:4). The aq. layer was lyophilized. Sugars were then extracted with pyridine and sucrose was identified by CO-TLC with an authentic sample (silica gel, EtOAc-

MeOH-H,O-HOAc, 65: 15: 15:20). Detection was with naphthoresorcine reagent.

Acidic hydrolysis of compounds l-3. The compound (1 mg) was refluxed with 2 N HCI (5 ml) for 1 hr. The solution was extracted with Et,O. Aq. layer was treated as described above. Fructose and glucose were identified by co-TLC. Detection was with p-anisidine phthalate and naphthoresorcinol reagents.

~-D-(3-O-Sinapoy~)~uctofuranosy~-or-D-(6-O-sinapoy~) glucopyranoside (1). Yellow amorphous powder; mp 1388141”; TLC (silica gel), EtOAc-MeOH-H,O (100: 14:7) (system A): R, 0.29; [r&,--94” (MeOH: c 0.2); UV i/z” nm (log c): 230 (4.52), 239 (4.60) 330 (4.67); I%;% 259, 396; EL:;;‘,“: 239, 330; ;.$;,L3+“c’: 239, 330;

~~$‘*‘: 390; ~~$Ac+HsBoJ: 330; FABMS (neg. ion mode) m/z: 753 [M-H]-, 547 [M-H-206]-, 367 [M - H - 286]-; D/CIMS (NH,, positive ion mode) m/z: 772

[M+NH,I+, 566 [M+NH,-206]+, 404 [M+NH, -162-206]+, 386 [M+NH,-180-206]+, 360 [M

+NH,-412]+; ‘HNMR (200 MHz, CD,OD): 67.67, 7.59 (lH,each, d,J= 16.0Hz. H-7”, H-7”‘) 6.91, 6.87(2H, each, s, H-2”, H-2”‘, H-6”, H-6”‘), 6.46,6.44 (1 H, each, d, J = 16.0Hz, H-8”, H-8”‘), 5.52 (lH, d, J=7.9Hz, H-3), 5.50 (lH,d,J=3,7Hz,H-1’),4.68(1H,brd,J=lO.OHz,H,-6’), 4.51 (lH, t, J=7.9 Hz, H-4), 4.30-4.19 (unres. H-5’ and Hi,-6’), 3.96-3.82 (unres. H-5, H,-6 and Hi,-6), 3.86, 3.83 (6H, each, s, MeO-3”, MeO-3”‘, MeO-5”, MeO-5”‘) 3.68 (lH, t, J=9.5Hz, H-3’), 3.62 (2H, s, H,-1 and H,-1), 3.50 (lH, dd, J=9.5, 3.7H2, H-2’), 3.38-3.29 (lH, m, H-4’); ‘H NMR (200 MHz, DMSO-d,): see Table 1; 13C NMR (50.3 MHz, CD,OD): 6 169.0 (C-9”‘) 168.1 (C-9”). 149.3 (C-3”, C-3”‘, C-5”, C-5”‘) 147.8, 147.2 (C-7”, C-7”‘), 139.5 (C-4”, C-4”‘) 126.5, 126.4 (C-l”, C-l”‘), 115.8, 115.4 (C-8”, C-S”‘), 107.0, 106.9 (C-2”, C-2”‘, C-6”, C-6”‘), 104.8 (C-2), 92.6 (C-l’), 84.3 (C-5), 79.3 (C-3), 75.0 (C-3’), 74.2 (C-4), 73.1 (C-2’), 72.4 (C-5), 71.9 (C-4’). 65.7 (C-l), 65.6 (C-6’), 63.7 (C-6), 56.9, 56.8 (MeO-3”, MeO-3”‘, MeO-5”, MeO- 5”‘); 13C NMR (50.3 MHz, DMSO-d,): see Table 2.

P-D-(3-O-Sinapoyl)fructofuranosyl-a-D-(3-0-acety1-6- 0-sinapoyl)glucopyranoside (2). Yellow amorphous pow- der; mp 131-135”; TLC (system A): R,0.38; [xl,-28” (MeOH; c 0.2); UV J.z$‘H nm (log E): 227(4.57), 239(4.58), 329 (4.62); I::? 258, 396; /i;;t’? 238, 329; ~;‘,C,+HC’: 239 33@ If(l”,Ac: 332, 390; IZ~:Ac+H3B03: 330; FABMS > 3 (neg. ion mode)m/z: 795 [M-H]-, 589 [M-H-206]-, 367 [M-H-428]-; ‘HNMR (200 MHz, DMSO-d,): see Table 1; i3CNMR (50.3 MHz, CD,OD): S 172.7 (MeCOO), 168.9 (C-g”‘), 168.3 (C-g”), 149.3 (C-3”, C-3”‘, C-5”, C-5”‘), 147.8, 147.3 (C-7”, C-7”‘), 139.5 (C-4”, C-4”‘), 126.6, 126.5 (C-l”, C-l”‘), 115.7, 115.5 (C-8”, C-S”‘), 107.1, 106.9 (C-2”, C-2”‘, C-6”, C-6”‘), 104.8 (C-2), 92.6 (C-l’), 84.3 (C-S), 79.3 (C-3), 76.9 (C-3’), 74.2 (C-4), 72.4 (C-S), 71.3, (C-2’), 70.0 (C-4’), 65.5 (C-61, 65.3 (C-l), 63.8 (C-6), 56.8 (MeO-3”, MeO-3”‘, MeO-5”, MeO-5”‘), 21.1 (MeCOO); 13C NMR (50.3 MHz, DMSO-d,): see Table 2.

P-D-(3-O-Sinapoyl)fructofuranosyl-cr-D-(4-o-~etyI-6- 0-sinapoyflglucopyranoside (3). Yellow amorphous pow- der; mp 124-127”; TLC (system A): R,0.34; [c~]~--70” (MeOH; c 0.2); UV L$‘” nm (log E): 228 (4.53), 239 (4.56), 329 (4.62); ,igyMde: 259, 396; i;1,c,“; 239, 330; I;;:3+HCI*

Sinapic acid esters from Polygala uirgata 145

239 330 IzzAc: 331, 391; l~~~Ac+H3Bos: 330; FABMS (neg. ion’mode) m/z: 795 [M-H]-, 589 [M-H-206]-; D/CIMS (NH,, positive ion mode) m/z: 898[M+NHI +84]+, 856 [M+NH,+42]+, 814 [M+NHA+, 772 [M+NH4-42]+, 650 [M+NH,+42--206]+, 608 CM +NH*-206]+; ‘HNMR (200 MHz, CD,OD): 67.66, 7.62 (lH, each, d, J= 15.9Hz, H-7”, H-7”‘), 6.95,6.88 (2H, each, s, H-2”, H-2”‘, H-6”, H-6”‘), 6.46,644 (lH, each, d, J =159Hz,H-8”,HX’), 5.54(1H,d,J=3.7Hz,H-1’),5.44 (lH, d,J=6.9Hz, H-3),4.74(1H, t, J=9.8Hz, H-4’), 4.45 (lH, t, J = 6.9 Hz, H-4), 4.28-4.38 (unres. H-S and H&-6’), 4.08-4.13 (lH, H,-6’1, 3.83-4.06 (unres, H-5, H,-6, and H,,-6), 3.88,3.85 (6H, each s, MeO-3”, MeO-3”‘, MeO-5”, MeO-S”), 3.75 (HI, t, J=9.8Hz, H-3’), 3.65 (2H, d, J =3.4Hz, H,-1 and H,l), 3.54(1H,dd, 3=9.8, 3.7Hz, H- 2’), 1.97 (3H, s, OAc); 13CNMR (50.3 MHz, CD,OD): 6 172.1 (MeCOO), 168.8 (C-9”‘), 168.0 (C-9”), 149.6, 149.4 (C-3”, C-3”‘, C-5”, C-5”‘), 147.9, 147.6 (C-7”, C-7”‘), 139.9 (C-4”, C-4”‘), 126.5 (C-l”, C-l”‘), 115.6, 115.3 (C-8”, C-8”‘), 107.3,107.O(C-2”, C-2”‘, C-6”, C-6”‘), 105.6 (C-2), 92.7 (C- l’), 85.1 (C-5), 79.9 (C-3), 74.7 (C-4), 73.0” (C-4’), 72.8* (C- 2’), 72.7a (C-3’), 70.5 (C-S), 65.9 (C-l, C-6’), 63.7 (C-6), 57.0, 56.9 (MeO-3”, MeO-3”‘, MeO-S’, MeO-5”‘), 20.7 MeCOOk ‘H NMR (200 MHz, DMSO-d,): see Table 1; t3C NMR (50.3 MHz, DMSO-I,): see Table 2. “Assign- ments interchangeable.

Ack~owZedge~n~s-Financial support has been pro- vided by the Swiss National Science Foundation, the Sandoz Foundation, Basel, and the Herbette Foundation of the University of Lausanne. A studentship was awar- ded to A.B. by the Swiss Commission F&deraIe des Bourses pour Etudiants Etrangers. The Directorate for Development Cooperation Humanitarian Aid (Swiss Federal Department of Foreign Affairs) is acknowledged for a travel grant.

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18.

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