Synthesis of 5-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin

Article abstract of DOI:10.1080/10286020.2011.572552

The synthesis of title isocoumarin, the 5-chloro analog of naturally occurring 7-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin, isolated from Tessmannia densiflora is described. Chlorination of ethyl 2-(2-ethoxy-2- oxoethyl)-4,6-dimethoxybenzoate (2) aff

Full text of DOI:10.1080/10286020.2011.572552

Journal of Asian Natural Products Research
Vol. 13, No. 6, June 2011, 505–511
Synthesis of 5-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin
Aamer Saeed*
Department of Chemistry, Quaid-I-Azam University, 45320 Islamabad, Pakistan
(Received 13 December 2010; final version received 13 March 2011)
The synthesis of title isocoumarin, the 5-chloro analog of naturally occurring 7-chloro-8-
hydroxy-6-methoxy-3-pentylisocoumarin, isolated from Tessmannia densiflora is
described. Chlorination of ethyl 2-(2-ethoxy-2-oxoethyl)-4,6-dimethoxybenzoate (2)
afforded 3-chloro ester (3) followed by hydrolysis to furnish the 2-(carboxymethyl)-3-
chloro-4,6-dimethoxybenzoic acid (4) that was converted to corresponding anhydride
(5). Condensation of the latter with hexanoyl chloride in the presence of
tetramethylguanidine and triethyl amine afforded 5-chloro-6,8-dimethoxy-3-pentyliso-
coumarin (6) which upon regioselective demethylation yielded the title isocoumarin (1).
Keywords: chlorinated isocoumarins; Tessmannia densiflora; 2-chloro-3,5-dimethoxy
homophthalic acid
1. Introduction
diachlorodiaportin and related isocoumar-
ins from lichen Graphis sp. [12], chaeto-
chiversins A and B from Chaetomium
chiversii [13], avicennin A (5-chloro-6,8-
dihydroxy-3-methylisocoumarin) from
mangrove endophytic fungus in south
China sea [14], TMC-264, a novel tricyclic
heptaketide from Phoma sp. [15], graphi-
slactone G, a chlorinated resorcylic
lactone from Graphis scripta [16], and 5-
chloro-4,6-dihydroxymellin from Cepha-
losporium acremonium [17]. Recently,
Nkunya and coworkers (2009) during
investigations for botanical insecticides
for the control of malaria-transmitting
Anopheles gambiae mosquitoes isolated
among other compounds 8-hydroxy-6-
methoxy-3-pentylisocoumarin and 7-
chloro-8-hydroxy-6-methoxy-3-pentyliso-
coumarin from the stem and root bark
extracts of Tessmannia densiflora Harms
(family Caesalpiniaceae) that showed
mosquito larvicidal activity [18].
Almost 300 isocoumarins and dihydroiso-
coumarins that have been isolated from
various natural sources [1–3]; however,
only a few chlorine-substituted isocoumar-
ins are found in nature. These include 5-
chloro-8-hydroxy-6-methoxy-3-methyli-
socoumarin [4] and its dihydroisocou-
marin [5], 7-chloro-8-hydroxy-6-methoxy-
3-methylisocoumarin and its dihydroiso-
coumarin and 5,7-dichloro-8-hydroxy-6-
methoxy-3-methylisocoumarin isolated
from Periconia macrospinosa, Swartzia
laevicarpa, Tovimita brasiliensis, and
Sporormia affinis [6], ochratoxins A–C
[7] and its methyl ester [8] from Aspergil-
lus ochraceus, 4-hydroxyochratoxin A
from Penicillium virdicatin [9], 5-chloro-
8-hydroxy-4-hydroxymethy-3-methyliso-
coumarin from Heterobasidion annosum
[10], 4-chloro-8-hydroxy-6-methoxy-3,5-
dimethyl-3,4-dihydroisocoumarin deriva-
tives from Lachnum papyraceum [11],
*Email: aamersaeed@yahoo.com
ISSN 1028-6020 print/ISSN 1477-2213 online
q 2011 Taylor & Francis
DOI: 10.1080/10286020.2011.572552
http://www.informaworld.com

506
A. Saeed
(1a) for comprehensive bioevaluation and
comparison (Figure 1).
R1
5
4
1'
5'
H3CO
R2
2. Results and discussion
O
1
7
The synthetic pathway employed to pre-
pare the target compound is outlined
in Scheme 1. Ethyl 2-(2-ethoxy-2-
oxoethyl)-4,6-dimethoxybenzoate (2)
obtained by the esterification of 2-(3,5-
dimethoxyphenyl)acetic acid was con-
verted into ethyl 3-chloro-2-(2-ethoxy-2-
oxoethyl)-4,6-dimethoxybenzoate (3) by
reaction with N-chlorosuccinimide (NCS)
in dry DMF. The structure was ascertained
on the basis of IR, NMR, and mass spectral
characteristics and elemental analysis. IR
spectrum showed peaks at 2978 (CZH),
1722 (CvO), 1591 (CvC), 1077 (CZO)
cm21 and a characteristic peak at
OH
O
1a R1 = H, R2 = Cl
R1 = Cl, R2 = H
1
Figure 1. Structures of compounds 1a and 1.
As a continuance of our endeavors in the
synthesis,characterization,crystalstructure,
and bioevaluation of this important class of
natural lactones [19–21], a synthesis of the
title compound was undertaken as the 5-
chloro analog (1) of the natural 7-chloro-8-
hydroxy-6-methoxy-3-pentylisocoumarin
Cl
3
H3CO
H3CO
COOEt
2
COOEt
5% KOH/EtOH
NCS, DMF
1
rt, 24 h (65%)
Reflux, 3 h (90%)
COOEt
COOEt
6
OCH3
OCH3
Cl
(3)
(2)
Cl
H3CO
5
H3CO
O
COOH
OH
4
1
3
(i) TMG/MeCN, 0°C
(ii) Et3N
(iii) C6H13COCl
Ac2O/dry toluene
O
(85%)
8
(71%)
O
OCH3
Cl
O
(4)
(5)
OCH3
Cl
H3CO
C5H11
C5H11
H3CO
AlCl3 anhyd./dry Et2O
(64%)
O
O
O
(6)
(1)
OH
OCH3
O
Scheme 1. Synthesis of 5-chloro-8-hydroxy-6-methoxy-3-pentylisocoumarin.

Journal of Asian Natural Products Research
507
680 cm21 for (CZCl) indicated the sub-
stitution of chloro group on the ring. The
1H NMR spectrum showed the triplet and
quartets of ethyl groups of the phenacetyl
ester moiety slightly upfield as compared
with the corresponding signals for benzoyl
ester moiety and a singlet at 6.94 ppm for
H-5 aromatic proton. In 13C NMR
spectrum, the carbonyl carbon of phena-
cetyl ester appeared at 169.5 ppm and that
of benzoyl ester carbonyl at 166.7 ppm.
A peak at 106.6 ppm is indicative of the
carbon attached to the chloro group. The
structure was finally confirmed by single
crystal X-ray diffraction data, which
unequivocally showed that chlorination
had taken place regioselectively at the
less-hindered 3- rather than the 5-position
on the ring. The molecular structure
of compound 3 is shown in Figure 2.
It crystallizes in the monoclinic space
group P2(1)/c with Z ¼ 4 and unit cell
dimensions: a ¼ 8.6616(6), b ¼ 22.3998
Alkaline hydrolysis of chloro diester
(3) afforded 2-(carboxy methyl)-3-chloro-
4,6-dimethoxybenzoic acid (4) as the key
intermediate. IR spectrum showed a broad
peak of OH groups of acid at 3500 cm21
,
indicating the hydrolysis of ester to acid
functionality in addition to those at 2990
(CZH), 1722 (CvO), 1586 (CvC), 1081
1
(CZO), and 652 (CZCl) cm21. The H
NMR spectrum of chlorinated homophtha-
lic acid showed broad peaks at 11.2 and
11.0 ppm for two OH of carboxylic acid
groups, whereas the peaks in the alkyl
region were absent. In 13C NMR spectrum,
the carbonyl carbons of phenacetyl
appeared at 173.3 ppm and those of
benzoyl ester carbonyl group at
169.4 ppm.
Diacid (4) was smoothly converted
into 5-chloro-6,8-dimethoxyiso chroman-
1,3-dione (5) by refluxing with acetic
anhydride in dry toluene. In IR spectrum
of the anhydride, the peaks for OH group
of acid were absent whereas peaks at 1797
and 1749 cm21 indicated the anhydride
functionality. H-7 appeared at d 6.56, CH2
˚
(16), c ¼ 8.9963(7) A, a ¼ 908, b ¼
114.351(2)8, g ¼ 908, and V ¼ 1590.2(2)
3
A [22].
˚
Figure 2. X-ray crystal structure of compound 3.

508
A. Saeed
at d 3.94, and MeO at d 4.05 ppm. In 13C
NMR spectrum, the carbonyls appeared at
d 168.0 and 162.7, CH2 at d 38.4, and MeO
at d 57.3.
acetone-d6 solutions at 300 and 75.4 MHz,
respectively, using Bruker AM-300 spec-
trophotometer. FT-IR spectra were
recorded using an FTS 3000 MX spectro-
photometer; Mass spectra (EI, 70 eV) with
a GC-MS instrument and elemental ana-
lyses with a LECO-183 CHNS analyzer.
All compounds were purified by thin layer
chromatography using silica gel from
Merck (Darmstadt, Germany).
Reaction of anhydride 5 with hexanoyl
chloride in the presence of 1,1,3,3-tetra-
methylguanidine (TMG) and triethyl
amine [23] furnished 5-chloro-6,8-
dimethoxy-3-pentylisocoumarin (6) in
71% yield. IR spectrum showed absorption
bands of 2998 (CZH), 1713 (CvO), 1585
(CvC), 1086 (CZO), and 646 (CZCl)
cm21. Isocoumarin 6 exhibited the charac-
teristic singlet for H-4 olefinic proton at d
6.50, the triplet for H-10 at d 2.47
(J ¼ 7.1 Hz), and the carbon signals at d
103.4 (C-4), 159.6 (C-3), and 163.2
(CvO).
Crystallographic data were collected
on a Bruker-AXS SMART APEX CCD
diffractometer. The crystal structure was
solved by direct methods. H-atoms were
located from difference Fourier maps and
then refined at idealized positions with a
riding model. CCDC 804525 contains the
supplementary crystallographic data for
this paper. These data can be obtained free
of charge from the Cambridge Crystal-
lographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif. or by e-mailing
data_request@ccdc.cam.ac.uk, or by con-
tacting The Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge
CB21EZ, UK.
6,8-Dimethoxy isocoumarin 6 was
regioselectively demethylated at C-8
methoxyl using anhydrous aluminum
chloride in dry ether [24], due to chelation
of the resulting hydroxyl with periplanar
lactonic carbonyl to yield 5-chloro-8-
hydroxy-6-methoxy-3-pentylisocoumarin
(1). Besides the disappearance of C-8
methoxyl, the downfield shift of singlet for
H-4 was detected. A similar shift for C-4
and C-3 (d 103.1 and 159.7), respectively,
was also noted in 13C NMR spectrum. The
lactonic carbonyl absorption was also
lowered to 1681 cm21 due to chelation
with C-8 hydroxyl that appeared at
11.2 ppm.
3.2 Ethyl 3-chloro-2-(2-ethoxy-2-
oxoethyl)-4,6-dimethoxybenzoate (3)
To a stirred solution of ethyl 2-(2-ethoxy-
2-oxoethyl)-4,6-dimethoxybenzoate (2)
(1.00 g, 3.38 mmol) in dry DMF (10 ml)
was added NCS (0.45 g, 3.4 mmol) and the
reaction mixture was stirred at room
temperature for 24 h. The reaction mixture
was poured into ice cold water (100 ml)
and extracted with ethyl acetate
(3 £ 50 ml). The combined organic
phase was separated, dried (MgSO4), and
concentrated to yield a solid. This was
recrystallized from ethanol to leave 3 as
colorless crystals (0.72 g, 2.2 mmol,
65.0%), Rf: 0.7 (petroleum ether: ethyl
acetate; 4:1), m.p. 95–978C; IR (KBr): n
2978 (CZH), 1722 (CvO), 1591 (CvC),
1077 (CZO), 680 (CZCl) cm21; 1H NMR
(CDCl3, d ppm): d 6.94 (1H, s, H-5), 4.35
(2H, q, J ¼ 7.2 Hz, CH2CH3), 4.16 (2H, q,
A comparison of the spectral data of 1
with those of the naturally occurring C-7
analog 1a indicates that in compound 1, H-
5 and C-5 rather than H-7 and C-7
appeared downfield in addition to other
slight changes.
3. Experimental
3.1 General experimental procedures
Melting points were recorded using a
digital Gallenkamp (SANYO, Leicester,
UK) model MPD BM 3.5 apparatus and
1
are uncorrected. H NMR and 13C NMR
spectra were determined in CDCl3 or

Journal of Asian Natural Products Research
509
J ¼ 7.2 Hz, CH2CH3), 3.93 (6H, s,
2 £ OCH3), 3.81 (2H, s, Ar-CH2), 1.34
(3H, t, J ¼ 7.8 Hz, ZCH2CH3), 1.25 (3H,
t, J ¼ 7.8 Hz, ZCH2CH3); 13C NMR
(CDCl3 d ppm): d169.5 (CvO), 166.7
(CvO), 157.7, 156.5, 134.0, 117.0, 115.6,
106.6, 61.4 (2 £ C) (2C, CH2CH3), 56.3,
39.5, 14.1 (2 £ CH3); MS (70eV): m/z (%)
330 [M]þ·(46), 332 [M þ 2]þ· 193 (2 £ C)
(43), 165 (100), 59 (12); Elemental
analysis: Found: C, 54.13%, H, 5.81%;
calcd for C15H19ClO6: C, 54.47%, H,
5.79%.
water. The organic layer was separated,
dried (MgSO4), and concentrated to yield
5 as colorless solid (0.47 g, 1.85 mmol,
85%); m.p. 1908C (decomp). IR (KBr): n
2948 (CZH), 1797 (CvO), 1749 (CvO),
1
1566 (CvC), 1081, 658 cm21. H NMR
(CDCl3, d ppm): d 6.56 (1H, s, H-7), 4.05
C
(6H, s, 2 £ OCH3), 3.94 (2H, s, CH2); 13
NMR (CDCl3, d ppm): d 168.0 (C3, CO),
162.7 (C1, CO), 160.2, 138.4, 106.2
(C8a), 109.9 (C5), 107.3, 103.1, 57.3
(2 £ OCH3), 38.4 (CH2), MS (70 eV): m/z
(%) 256 [M]þ·(46), 258 [M þ 2]þ,
193(43), 165(100), 59(12); Elemental
analysis: Found: C, 51.56; H%, 3.59%;
calcd for C11H9ClO5: C, 51.48%; H,
3.53%.
3.3 2-(Carboxymethyl)-3-chloro-4,6-
dimethoxybenzoic acid (4)
Potassium hydroxide (5%, 40 ml) was
added to a solution of (3) (1.0 g,
3.03 mmol) in ethanol (20 ml). The reaction
mixture was refluxed for 3 h. The solvent
was rotary evaporated, and cold water
(10 ml) was added and the reaction mixture
acidified using concn. hydrochloric acid.
The solid was filtered and recrystallized
from MeOH to give 4 (0.74 g, 2.72 mmol,
90%). m.p. 2408C (decomp). IR (KBr) n
3500 (CZH), 2990 (ArZCZH), 1722
3.5 5-Chloro-6,8-dimethoxy-3-
pentylisocoumarin (6)
A solution of 5 (0.4 g, 1.56 mmol) in
acetonitrile (15 ml) was added slowly to a
solution of TMG (0.2 g, 1.71 mmol) in
acetonitrile (5 ml), while maintaining
the internal temperature #08C. Triethyl
amine (0.3 ml, 3.12 mmol) was added in a
single portion, followed by dropwise
addition of hexanoyl chloride (0.34 g,
2.5 mmol). The reaction mixture was
further stirred for 20 min, allowed to
warm to ambient temperature, and then
quenched by addition of 1 M HCl (15 ml).
The organic layer was separated, washed
with saturated brine, dried, and concen-
trated. The crude compound was purified
by thin layer chromatography followed by
recrystallization from methanol to yield
isocoumarin 6 (0.37 g, 1.1 mmol, 71%) as
colorless semisolid. IR (KBr): n 2998,
2849, 1713, 1605, 1585, 1086, 860, 835,
(CvO), 1586 (CvC), 1081, 652 cm21
;
1H NMR (acetone-d6, d ppm): d 11.2 (1H,
br s, COOH), 11.0 (1H, br s, COOH), 6.85
(1H, s, H-5), 3.98 (2H, s, Ar-CH2), 3.93
(6H, s, 2 £ OCH3); 13C NMR (CDCl3 d
ppm): d 173.3 (CvO), 169.7 (CvO),
159.2 (C-3, C-5), 138.4, 119.6 (C-4), 108.2,
68.6, 102.5, 55.3 (Ar-OCH3), 42.6 (CH2);
MS (70 eV): m/z (%) 274 [M]þ· (46), 276
[M þ 2]þ, 193 (43), 165 (100), 59 (12);
Elemental analysis: Found: C, 48.07%; H,
3.97%; calcd for C11H11ClO6: C, 48.10%;
H, 4.04%.
1
810, 646 cm21; H NMR (CDCl3): d 0.88
(t, J ¼ 7.1 Hz, 3H, H-50), 1.30 (m, 2H, H-
40), 1.35 (q, J ¼ 3.5 Hz, 2H, H-30), 1.67 (q,
J ¼ 7.1 Hz, 2H, H-20), 2.47 (2H, t,
J ¼ 7.1 Hz, H-10), 3.85 (s, 3H, MeO),
3.95 (s, 3H, MeO), 6.50 (s, 1H, H-4), 6.71
(s, 1H, H-7); 13C NMR (CDCl3): d 163.2
(CvO), 158.3 (C-6), 159.6 (C-3), 141.8
3.4 5-Chloro-6,8-dimethoxyisochroman-
1,3-dione (5)
A solution of diacid 4 (0.6 g, 2.2 mmol) in
dry toluene (10 ml) was treated with acetic
anhydride (0.3 ml). The reaction mixture
was refluxed for 1 h and then added to ice

510
A. Saeed
(C-9), 103.4 (C-4), 106.7 (C-5), 100.9 (C-
7), 99.9 (C-10), 55.3 (MeO), 56.6 (MeO),
33.3 (C-10), 31.1 (C-30), 26.4 (C-20), 22.3
(C-40), 14.2 (C-50); MS: m/z 338 (16), 340,
219 (18), 206 (52), 191 (15), 177 (27), 165
(14), 164 (98). Elemental analysis: Found:
C, 63.92%; H, 6.76%; calcd for
C18H23ClO4: C, 63.81%; H, 6.84%.
Acknowledgements
The author gratefully acknowledges a research
grant from the Higher Education Commission
of Pakistan under Project No. 20-Mis-
cel/R&D/00/3834.
References
[1] R.D. Barry, Chem. Rev. 64, 229 (1964).
[2] R.A. Hill, Prog. Chem. Nat. Prod. 49, 1
(1986).
3.6 5-Chloro-6-methoxy-8-hydroxy-3-
pentylisocoumarin (1)
[3] E. Napolitano, Org. Prep. Proced. Int. 29,
631 (1997).
[4] R.B. Filho, M.P.L. De Moreas, and O.R.
Gottlieb, Phytochemistry 19, 2003 (1980).
[5] R.B. Filho, C.A.S. Miranda, O.R. Got-
tlieb, and M.T. Magalhaes, Acta Amazo-
nica 12, 801 (1982).
[6] D. Glies and W.B. Turner, J. Chem. Soc.
C, 2187 (1969).
[7] R.E. Peterson and A. Ciegler, Appl.
Environ. Microbiol. 36, 613 (1978).
[8] P.S. Steyn and C.W. Holzapel, J. South
African Inst. 20, 186 (1967).
[9] F.C. Stormer, C.E. Hansen, J.I. Pedersen,
G. Hvistendahl, and A.J. Aasen, Appl.
Environ. Microbiol. 22, 1051 (1981).
[10] J. Cudaj and J. Podlech, Tetrahedron Lett.
51, 3092 (2010).
[11] D.M.X. Donnelly, N. Fukuda, I. Kouno,
M. Martin, and J. O’Reilly, Phytochem-
istry 27, 2709 (1988).
Aluminum chloride (0.3 g, 1.08 mmol)
was added to a stirred solution of 6
(0.35 g, 1.26 mmol) in freshly distilled dry
ether (40 ml). The reaction mixture was
refluxed for 6 h, then poured into ice-water
and acidified with 0.5 N HCl. The layers
were separated and the organic layer was
dried (MgSO4) and concentrated to yield 1
as colorless solid and this was aqueous
purified by thin layer chromatography
(petroleum ether: ethyl acetate; 8:2) to
afford pure compound 1 (0.20 g, 0.8 mmol,
64%). m.p.76–788C, IR (KBr): n 2945,
28421, 1681, 1605, 1585, 860, 835, 810,
1
645 cm21; H NMR (CDCl3) d: 0.90 (t,
J ¼ 7.1 Hz, 3H, H-50), 1.31 (m, 2H, H-40),
1.39 (q, J ¼ 3.5 Hz, 2H, H-30), 1.68 (q,
J ¼ 7.6 Hz, 2H, H-20), 2.49 (t, J ¼ 7.6 Hz,
2H, H-10), 3.85 (s, 3H, MeO), 6.18 (s, 1H,
H-4), 6.39 (d, J ¼ 2.2 Hz, 1H, H-7), 11.2
(1H, br s, OH); 13C NMR (CDCl3): d 164.4
(CvO), 163.7 (C-8), 163.3 (C-6), 159.7
(C-3), 142.4 (C-9), 103.1 (C-4), 102.9 (C-
5), 107.1 (C-7), 98.7 (C-10), 56.3 (MeO),
33.3 (C-10), 31.1 (C-30), 26.4 (C-20), 22.3
(C-40), 13.9 (C-50); MS: m/z 324 (37), 326,
206 (52), 191 (15), 177 (27), 164 (100),
149 (29); Elemental analysis: Found: C,
62.89%; H, 6.32%; calcd for C17H21ClO4
C, 62.86%; H, 6.52%.
[12] T.O. Larsen and J. Breinholt, J. Nat. Prod.
62, 1182 (1999).
[13] E.M.K. Wijeratne, P.A. Paranagama, and
A.A.L. Gunatilaka, Tetrahedron 62, 8439
(2006).
[14] J. Hiort, K. Maksimenka, M. Reichart, S.
Peroviae-Ottstadt, W.H. Lin, V. Wray, K.
Steube, K. Schaumann, H. Weber, P.
Proksch, R. Ebel, W. Mu¨ller, and E.G.
Bringmann, J. Nat. Prod. 67, 1532 (2004).
[15] M. Sakurai, M. Nishio, K. Yamamoto, T.
Okuda, K. Kawano, and T. Ohnuk, Org.
Lett. 5, 1083–1085 (2003).
¨
[16] K. Krohen, R. Bahramsari, U. Florke, K.
Ludewig, C. Klichespory, A. Michel, H.J.
Aust, S. Draeger, B. Schulz, and S. Antus,
Phytochemistry 45, 313 (1997).
[17] M.H.H. Nkunya, C.C. Joseph, S.M.
Magesa, A. Hassanali, M. Heydenreich,
and E. Kleinpeter, Phytochemistry 70,
1233 (2010).
4. Conclusion
[18] J. Cudaj and J. Podlech, Tetrahedron Lett.
51, 3092 (2010).
[19] A. Saeed, Helv. Chim. Acta 86, 377
(2003); A. Saeed, Nat. Prod. Res. 18, 373
(2004).
An efficient synthesis of the unnatural
analog of a naturally occurring isocoumarin
was carried out for complete bioevaluation
and comparison.

Journal of Asian Natural Products Research
511
[20] A. Saeed and S. Ehsan, J. Braz. Chem.
Soc. 16, 739 (2005); A. Saeed, J. Asian
Nat. Prod. Res. 8, 417 (2006).
Cambridge Crystallographic Data Centre.
Available from: http://www.ccdc.cam.
ac.uk/datarequest/cif.
[21] A. Saeed, Syn. Commun. 37, 1485 (2007);
A. Saeed, J. Asian Nat. Prod. Res. 12, 88
(2010).
[23] W.E. Bauta, D.P. Lovett, W.R. Cantrell, Jr.,
and B.D. Burke, J. Org. Chem. 68, 5967
(2003).
[22] CCDCNo. 804525, Supplementarycrystal-
lographic data for this paper. These data
can be obtained free of charge from the
[24] T.R. Govindachari, P.C. Parthasarathy,
H.K. Desai, and K.S. Ramachandran,
Indian J. Chem. 13, 537 (1975).

Copyright of Journal of Asian Natural Products Research is the property of Taylor & Francis Ltd and its content
may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express
written permission. However, users may print, download, or email articles for individual use.