Isolation and synthesis of analgesic and anti-inflammatory compounds from Ochna squarrosa L.

Article abstract of DOI:10.1016/j.bmc.2006.06.048

Two new furanoflavonoids (1, 2), one new chalcone dimer (3) along with six known compounds, chrysophanol, 5-O-methyl squarrosin, 5-methoxy furano[4″,5″,6,7]flavone, calodenone, lophirone A and lophirone H were isolated from the ethyl acetate-soluble fraction of methanol extract of root bark of Ochna squarrosa. Chrysophanol, calodenone, lophirone A and lophirone H were isolated from this plant for the first time. The structures of all the isolated compounds were confirmed by 1D and 2D spectroscopic data. These compounds were tested for analgesic and anti-inflammatory activity. All the new compounds showed good analgesic and anti-inflammatory activity. A simple and facile method for the cleavage of benzyl ethers using I₂ in trigol is also reported.

Full text of DOI:10.1016/j.bmc.2006.06.048

Bioorganic & Medicinal Chemistry 14 (2006) 6820–6826
Isolation and synthesis of analgesic and anti-inflammatory
compounds from Ochna squarrosa L.
V. Anuradha,a Pullela V. Srinivas,a R. Ranga Rao,a K. Manjulatha,b
Muralidhar G. Purohitb and J. Madhusudana Raoa,*
aNatural Products Laboratory, Organic Division-I, Indian Institute of Chemical Technology, Hyderabad 500 007, India
bDepartment of Chemistry, University of Gulbarga, Gulbarga, India
Received 2 June 2006; revised 19 June 2006; accepted 20 June 2006
Available online 7 July 2006
Abstract—Two new furanoflavonoids (1, 2), one new chalcone dimer (3) along with six known compounds, chrysophanol, 5-O-
methyl squarrosin, 5-methoxy furano[400,500,6,7]flavone, calodenone, lophirone A and lophirone H were isolated from the ethyl ace-
tate-soluble fraction of methanol extract of root bark of Ochna squarrosa. Chrysophanol, calodenone, lophirone A and lophirone H
were isolated from this plant for the first time. The structures of all the isolated compounds were confirmed by 1D and 2D spec-
troscopic data. These compounds were tested for analgesic and anti-inflammatory activity. All the new compounds showed good
analgesic and anti-inflammatory activity. A simple and facile method for the cleavage of benzyl ethers using I2 in trigol is also
reported.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
method for the cleavage of benzyl ethers was also
observed. The scope and generality of the method
was extended to many other compounds with differ-
ent functionalities. Analgesic and anti-inflammatory
activity of the isolated compounds has been
investigated.
Ochna squarrosa commonly known as ‘sunari’ or ‘yer-
ra juvvi’ belongs to the family Ochnaceae. It is a small
shrub, grows up to 50 cm tall with thin, dark brown
stem.1 In traditional systems of medicine, it is consid-
ered as one of the important drug used in the treat-
ment of various conditions like constipation, ulcers,
sores and cancers. Its root bark is used as a digestive
tonic.2 Boiled leaves of O. squarrosa are used in the
treatment of lumbago and ulcers. Decoction of its
root is used in the treatment of menstrual complaints
and asthma.
2. Chemistry
2.1. Isolation and structure elucidation
Compound 1 was obtained as a pale yellow amor-
phous solid, mp 272 ꢁC and was analyzed for
C18H12O5 by HRESIMS and 13C NMR data. In
the IR spectrum absorption bands at 3426 cmꢀ1
and 1623 cmꢀ1 suggested the presence of a hydroxyl
group and an a,b-unsaturated carbonyl group. The
In this paper, we report isolation of two new fur-
anoflavonoids and one new chalcone dimer together
with six other known compounds, chrysophanol,3 5-
O-methyl squarrosin,4 5-methoxy furano[400,500,6,7]fla-
vone,5 calodenone,6 lophirone A7 and lophirone H.8
Synthesis of two new furanoflavonoids is also report-
ed. The synthesis of furanoflavonoids began with res-
1
200 MHz H NMR spectrum in Me2CO-d6 displayed
a singlet at d 3.96 integrating for three protons indi-
cating the presence of a methoxyl group attached to
an aromatic ring. The position of methoxyl group
on the aromatic ring was established from NOE
acetophenone.
furanochalcone to furanoflavone, a simple and facile
During
the
cyclization
of
experiment. Irradiation of methoxyl group at
d
3.96 resulted in an enhancement of H-20 signal indi-
cating that the methoxyl group is attached at C-30
of ring C.
Keywords: Ochna squarrosa; Furanoflavanoid; Chalcone dimer; Anal-
gesic activity; Anti-inflammatory activity.
*
Corresponding author. E-mail: janaswamy@iict.res.in
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.06.048

V. Anuradha et al. / Bioorg. Med. Chem. 14 (2006) 6820–6826
6821
group. Thus, the structure of compound 2 was con-
firmed as 30, 40-dihydroxyfurano[400,500,6,7]flavone. The
structures of compound 1 and compound 2 were further
confirmed by their synthesis.
5'
OR1
OR2
6'
C
8
B
5
O
A
2
O
2'
2"
3
3"
O
1. R1 = H, R2 =Me
2. R1 = H, R2 =H
3
OH
3'
5''
Compound 3 was isolated as a pale yellow amorphous
solid, with mp 262 ꢁC analyzed for C30H24O9 using
HRESIMS and 13C NMR spectral data. A combination
of HRESIMS (M+ꢀ1; 527) and 13C NMR results indi-
cated that compound 3 has a symmetrical structure.
IR spectrum of compound 3 displayed absorption bands
at 3384 cmꢀ1 and 1633 cmꢀ1 suggesting the presence of
a hydroxyl group and a chelated carbonyl group,
respectively.
2
6'"
1"
HO
3
6
3''
'
β
β
HO
OH
O
'
4
2
2"
5
2'
3'"
2'"
'
β
β
O
5
5''
α
α
O
6''
OH
6' H
H
H
H
c
5'
6''' 5'''
O
4'
α α
5'
'
2"
3"
6"
5"
HO
OH
HO
2'
O
O
2''' 3'''
3'
OH
HO
OH
4. Lophirone H
3. Lopjhirone L
1H NMR spectrum further has a singlet at d 6.96 inte-
grating for one proton, attributed to an olefinic proton,
which is adjacent to the carbonyl group. Two doublets
at d 7.06 (J = 8.8 Hz), 7.56 (J = 2.4 Hz) and a double
doublet at d 7.66 (J = 8.4 Hz, 2.4 Hz) each integrating
for one proton suggested the presence of a 1,3,4-trisub-
stituted aromatic ring. A doublet at d 8.20 (J = 2.0 Hz)
and a double doublet at d 7.12 (J = 1.2 Hz, 2.4 Hz) inte-
grating for one proton each indicated the H-200, H-300 of
the furan ring. A doublet at d 8.10 (J = 1.2 Hz) and a
singlet at d 8.40 each integrating for one proton indicat-
ed the presence of a 1,2,4,5-tetrasubstituted aromatic
ring. A singlet at d 9.98 is due to the presence of a
hydroxyl group. The explanation is further supported
by the disappearance of a peak at d 9.98 in a heavy water
exchange condition.
1
The H NMR spectrum of compound 3 in Me2CO-d6
showed signals for 12 protons. Two doublets at d 6.80
and d 7.40 each integrating for two protons suggested
the presence of a 1,4-disubstituted aromatic ring. Two
doublets at d 6.08 (J = 2 Hz) and d 7.38 (J = 8 Hz) each
integrating for one proton and a double doublet at d
6.10 (J = 8 Hz, 2 Hz) integrating for one proton suggest-
ed the presence of a 1,2,4-trisubstituted aromatic ring. A
double doublet at d 5.42 (J = 8 Hz, 1.2 Hz) integrating
for one proton indicated the presence of a methine pro-
ton attached to an oxygen atom. Another double dou-
blet at d 4.72 (J = 8 Hz, 2 Hz) integrating for one
proton indicated the presence of a methine proton at-
tached to the carbonyl group. A singlet at d 12.50 inte-
grating for one proton indicated the presence of a
chelated hydroxyl group. The presence of hydroxyl
group was confirmed by deuterium exchange
experiment.
The appearance of H-5 proton as a singlet indicated the
annellation of furan ring to be at C-6/C-7 positions.
Further confirmation of the annellation of furan ring
at C-6/C-7 came from the long-range correlation of
H-300 proton at d 7.12 with the H-5 proton at d 8.40 in
1H–1H COSY experiment.
The 13C NMR spectrum of compound 3 showed only 15
signals whose multiplicity was explained using DEPT
and HMBC correlations. DEPT experiment showed that
there are no methylene carbons. Two signals at d 58.7
and d 83.8 indicated the presence of two aliphatic
The 13C NMR spectrum in Me2CO-d6 of compound 1
exhibits the presence of 18 carbon atoms whose multi-
plicity is explained using DEPT and HMBC correla-
tions. The DEPT experiment revealed the presence of
one methyl, eight methines and nine quaternary car-
bons. In the HMBC spectrum, absence of correlation
between H-300 proton and C-9 and correlations of H-300
with C-5, C-6 and C-10 clearly suggested the linear
fusion of the furan ring with the aromatic ring. Hence,
the structure of compound 1 was identified as 40-hy-
droxy-30-methoxyfurano[400,500,6,7] flavone.
1
methine carbons of tetrahydrofuran ring. The H–1H
COSY long-range spectrum showed a weak correlation
between H-60 of ring A0 and b proton of the furan ring
indicating that the benzoyl ring is attached to the a car-
bon and the phenyl group to the b carbon of the furan
ring.
The spectral data of compound 3 (1H and 13C) resem-
bled with those of lophirone G8 with slight variations,
but its optical rotation and melting point were found
to be different. This indicated that compound 3 has sim-
ilar structural framework as lophirone G with a differ-
ence in its absolute configuration.
Compound 2 was isolated as a pale yellow amorphous
solid, mp 282 ꢁC. The molecular formula is analyzed
as C17H10O5 using HRESIMS and 13C NMR data.
The spectral data of compound 2 were similar to those
obtained for compound 1. The significant difference in
The relative stereochemistry of the furan ring was estab-
lished with the help of NOESY experiment. The
NOESY spectrum of compound 3 showed a long-range
coupling between a and b protons of the furan ring indi-
cating a cis-stereochemistry between them. The relative
stereochemistry of the two protons at a and a0 was
explained on the basis of optical activity. If all the sub-
stituents on the furan ring of compound 3 were to be ar-
ranged in a cis configuration with respect to each other,
it would generate a plane of symmetry resulting it to be
1
the H NMR spectrum is the absence of a peak at d
3.96 suggesting the absence of methoxyl group in com-
pound 2. The disappearance of two signals at d 9.86
and d 9.88 in deuterium exchange conditions indicated
the presence of two phenolic hydroxyl groups. The
absence of a signal at d 56.4 in the 13C NMR spectrum
of compound 2 confirmed the absence of methoxyl

6822
V. Anuradha et al. / Bioorg. Med. Chem. 14 (2006) 6820–6826
optically inactive. But, compound 3 is optically active
with an optical rotation of ꢀ6.4ꢁ. This indicates that
compound 3 has a cis–trans–cis relative stereochemistry
at the furan ring. This was further confirmed by its NOE
spectrum. Irradiation of a proton at d 4.72 resulted in an
enhancement of b proton at d 5.42 indicating that the
two protons are in cis relative stereochemistry with each
other.
presence of KOH in anhydrous ethanol to give chalcone
9 or 10 which was cyclized using I2 in trigol10 at 120 ꢁC
to afford 40-hydroxy-30-methoxyfurano[400,500,6,7]flavone
(1) or 30,40-dihydroxyfurano[400,500,6,7]flavone (2)
(Scheme 1).
During the course of our studies towards the synthesis
of furanoflavonoids, compound 1 and compound 2, we
needed to synthesize furanoflavones 11 and 12 from
chalcones 9 and 10, respectively, using I2 in trigol7
(Scheme 2).
2.2. Synthesis
The synthesis began with resacetophenone. Resacetoph-
enone was treated with bromoacetaldehyde diethyl ace-
tal in the presence of potassium carbonate in anhydrous
DMF to give compound 5, which on treatment with
acidic Amberlyst 15 in toluene at 90 ꢁC yielded 5-ace-
tyl-6-hydroxycoumarone9 (6). 5-Acetyl-6-hydroxy cou-
marone was condensed with aldehyde 7 or 8 in the
1
Interestingly, the H NMR spectrum of the resultant
product showed the absence of characteristic benzyl
ether protons at their respective positions. The ESIMS
spectrum of the compounds obtained also revealed the
absence of benzyl ether group. Based on this, it was con-
cluded that benzyl ether in compounds 9 and 10 has
HO
OH
O
OH
BrCH2CH(OC2H5)2
Amberlyst 15
Toluene, 90oC
DMF/K2CO3, 80oC
EtO
OEt
O
O
5
OBn
O
OH
O
OH
OBn
OR
OR
OHC
7: R = Me
8: R = Bn
9: R = Me
10: R = Bn
6
O
O
OR1
OR2
I2, Trigol
O
O
O
120oC, 2h.
1: R1 = H, R2 = Me
2: R1 = R2 = H
Scheme 1.
OR1
OR2
O
OH
OBn
OR
O
O
O
I2, Trigol
120oC, 2h.
O
9: R = Me
10: R = Bn
11: R1 = Bn, R2 = Me
12: R1 = R2 = Bn
Scheme 2.

V. Anuradha et al. / Bioorg. Med. Chem. 14 (2006) 6820–6826
6823
OR1
OR2
OH
OR1
O
I2, Trigol
O
O
120oC, 2h.
OR2
O
9: R1 = Bn, R2 = Me
10: R1 = R2 = Bn
O
1: R1 = H, R2 = Me
2: R1 = R2 = H
Scheme 3.
been cleaved to give compounds 1 and 2 along with the
cyclization of chalcone to its corresponding flavone
(Scheme 3).
The percent analgesia are recorded at different time
intervals as shown in Table 3. The results of analgesic
activity indicate that all the test compounds have
exhibited significant activity at 25 mg/kg when com-
pared with the control, 1% Tween 80. The crude ex-
tract and compound 1 have promising protection at
early reaction time and potent than at standard reac-
tion time. The potent analgesic and anti-inflammatory
activity of the crude extract may be probably due to
the synergistic effect of the mixture of compounds in
natural proportion.
An extensive literature survey revealed that though
different methods are available for selective cleavage
of benzyl ethers, most of them suffer from certain
drawbacks such as lack of selectivity, reduction of
double bonds, etc. Prompted by this discovery, we
decided to extend our investigation to other sub-
strates and establish its wider11,12 applicability. The
scope and generality of this procedure is illustrated
with several examples and the results are summarized
in Table 1.
5. Experimental
5.1. Isolation procedures
3. Conclusion
The shade-dried root bark of O. squarrosa (8 kg) was
extracted with methanol to give 120 g of extract,
which was partitioned between ethyl acetate and
water. The ethyl acetate-soluble fraction (15 g) was
subjected to column chromatography over silica gel
(60–120 mesh, 300 g) and eluted with hexane/ethyl
acetate in the increasing order of polarities to afford
five fractions. Fraction 3 (hexane/ethyl acetate 90:10)
was further subjected to column chromatography
and eluted with hexane/ethyl acetate 95:5 to give com-
pound 1 (0.040 g) and compound 2 (0.020 g) upon elu-
tion with hexane/ethyl acetate 90:10. Fraction 5 was
further subjected to column chromatography and elut-
ed with hexane/ethyl acetate 75:25 to give compound 3
(0.012 g) and compound 4 (0.010 g) upon elution with
hexane/ethyl acetate 70:30.
Two new anti-inflammatory and analgesic furanoflav-
ones along with a new chalcone dimer were isolated
from O. squarrosa. The newly isolated furanoflavones
were also synthesized involving a new methodology of
benzyl deprotection. I2 in trigol was demonstrated to
be a simple and convenient reagent to cleave benzyl
ethers. The advantages of this method are inexpensive,
co-reagent not needed, simple reaction conditions, high
selectivity, retention of unsaturation, etc. These advan-
tages are very useful in complex multiple synthesis which
requires sequential protection and deprotection of vari-
ous functionalities.
4. Biological assay
Compound 1: [40-hydroxy-30-methoxyfurano[400,500,6,7]-
flavone]. Mp 272 ꢁC. IR (KBr) mmax 3426, 1623, 1298,
The crude extract and isolated compounds were tested
for analgesic (tail-flick method) and anti-inflammatory
(carrageenan-induced paw oedema method) activity,
diclofenac sodium was taken as reference standard.
The crude ethyl acetate-soluble fraction of the metha-
nol extract of root bark showed very promising anal-
gesic and anti-inflammatory activity. The paw oedema
percent protection values are shown in Table 2.
Among the tested samples crude extract has exhibited
promising percent protection at 25 mg/kg and is com-
parable to standard at 20 mg/kg. The isolated mole-
cules also could protect but they are comparable at
higher dose level than standard drug used in preset
investigation.
1
1109, 831, 569 cmꢀ1. H NMR (300 MHz, Me2CO-d6)
d 3.96 (3H, s, –OMe), 6.96 (1H, s, H-3), 7.06 (1H, d,
J = 8.8 Hz, H-50), 7.12 (1H, dd, J = 1.2 Hz, 2.4 Hz,
H-300), 7.56 (1H, d, J = 2.4 Hz, H-20), 7.66 (1H, dd,
J = 8.4 Hz, 2.4 Hz, H-60), 8.10 (1H, d, J = 1.2 Hz,
H-8), 8.20 (1H, d, J = 2 Hz, H-200), 8.40 (1H, s, H-5).
13C NMR (75 MHz, Me2CO-d6) d 56.4 (C–OMe),
101.6 (C-8), 105.2 (C-3), 108.0 (C-300), 110.2 (C-10),
112.4 (C-20), 118.0 (C-5), 120.4 (C-60), 124.0 (C-50),
124.0 (C-10), 126.8 (C-6), 149.6 (C-30), 149.8 (C-200),
152.4 (C-40), 154.0 (C-9), 157.6 (C-7), 163.8 (C-2),
178.0 (C@O). HRESIMS m/z [M++H] 309.0767, calcd
309.0763.

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V. Anuradha et al. / Bioorg. Med. Chem. 14 (2006) 6820–6826
Table 1. Selective cleavage of benzyl ethers using I2/trigol
Entry
1
Substrate
Product
Time (h)
Isolated yield (%)
OBn
OMe
OH
O
O
O
O
O
O
OMe
3
60
1b
1a
CHO
CHO
BnO
HO
2
3
65
OMe
OMe
2b
2a
OBn
OH
3
4
5
2
3
3
65
60
70
3b
3a
NO2
NO2
BnO
HO
HO
OMe
OMe
4b
4a
CO2Bn
CO2Bn
BnO
BnO
OH
OBn
5a
5b
6
7
2
3
70
65
O
6a
O
HO
O
O
6b
OH
OBn
7a
7b
OBn
OBn
OH
OH
O
O
O
O
O
8
9
3
3
70
70
O
8b
8a
CO2Bn
CO2Bn
BnO
HO
OMe
9a
OMe
9b
Table 2. Anti-inflammatory activity of Ochna squarrosa crude extract and compounds on the carrageenan-induced paw oedema of Albino rats
Treatment
Dose (mg/kg)
Paw oedema percent protection (h)
1/2
4.15 ( 0.37)
29* ( 0.04)
10.9* ( 0.005)
30** ( 0.004).
20* ( 0.017)
1
2
3
4
Control
Diclofenac sodium
Tween 80, 1%
4.19 ( 0.21)
37 ( 0.08)
43** ( 0.015)
40** ( 0.06)
34.7 ( 0.008)
48** ( 0.008)
3.31 ( 0.01)
50** ( 0.03)
30** ( 0.02)
47** ( 0.02)
37** ( 0.057)
2.47 ( 0.02)
2.3 ( 0.05)
20
25
25
25
25
46.5** ( 0.05)
21.74* ( 0.016)
42** ( 0.084)
33.4** ( 0.027)
43.7** ( 0.026)
33.5** ( 0.03)
18.5* ( 0.015)
34** ( 0.055)
16.7* ( 0.008)
36.9** ( 0.055)
1
2
3
Crude extract
43.7** ( 0.001)
52.3** ( 0.004)
Significance levels *p < 0.05, **p < 0.01 compared with respective control (ANOVA followed by Dunnett’s test). Each value represents SE (n = 6).

V. Anuradha et al. / Bioorg. Med. Chem. 14 (2006) 6820–6826
6825
Table 3. Analgesic activity effect of Ochna squarrosa crude extract and compounds in Swiss mice by tail-flick method
Treatment
Dose (mg/kg)
Percent analgesia (min)
120
30
60
90
150
180
Control
Diclofenac sodium 20
Tween 80, 1%
3.03 ( 0.03)
28.00 ( 0.07)
57.49** ( 0.98) 75.39** ( 0.65) 73.15** ( 1.68)
18.91** ( 0.90) 30.88** ( 0.33) 57.52** ( 0.09) 69.11** ( 1.09)
24.65** ( 1.38)
77.92** ( 0.07) 73.12** ( 0.07) 74.88** ( 01.0)
5.79 ( 0.03)
39.5** ( 0.13)
9.09 ( 0.03)
7.5 ( 0.05)
5.3 ( 0.02)
2.2 ( 0.02)
51.5** ( 0.09) 71.36** ( 0.13) 51.36** ( 0.11) 24.77** ( 0.05)
1
25
25
25
25
72.7** ( 1.57) 24.16** ( 0.79)
22.77 ( 1.04)
3.8 ( 0.58)
15.05 ( 0.34)
2
3
Crude extract
31.35 ( 0.41) 66.02** ( 0.73) 57.53** ( 0.85) 40.41** ( 0.73) 16.57** ( 0.78)
45.6 ( 0.03) 44.45** ( 0.30) 21.76** ( 0.32)
Significance levels **p < 0.01 compared with respective control Tween 80, 1% (ANOVA followed by Dunnett’s test). Each value represents SE
(n = 6).
Compound
vone]. Mp 282 ꢁC. IR (KBr) mmax 3414, 2924, 618,
1149, 1024, 770, 604 cmꢀ1 1H NMR (300 MHz,
Me2CO-d6) 6.70 (1H, s, H-3), 6.88 (1H, d,
2:
[30,40-dihydroxyfurano[400,500,6,7]fla-
5.3.2. Anti-inflammatory activity. Anti-inflammatory
activity was evaluated by carrageenan-induced paw
oedema test in rats.13 Diclofenac sodium 20 mg/kg
was administered as a standard for comparison and
test compounds, extract at dose level of 25 mg/kg
were administered orally. The paw volume was mea-
sured using the mercury displacement technique with
the help of plethysmograph immediately before and
30 min, 1, 2, 3 and 4 h after carrageenan injection.
The percent inhibition of paw oedema was
calculated.
.
d
J = 8.8 Hz, H-50), 7.12 (1H, dd, J = 1.2 Hz, 2.7 Hz,
H-300), 7.42 (1H, d, J = 2.4 Hz, H-20), 7.44 (1H, dd,
J = 8.4 Hz, 2.4 Hz, H-60), 8.00 (1H, d, J = 1.2 Hz,
H-8), 8.12 (1H, d, J = 2 Hz, H-200), 8.30 (1H, s, H-
5). 13C NMR (75 MHz, Me2CO-d6) d 101.0 (C-8),
104.3 (C-3), 107.8 (C-300), 113.9 (C-10), 116.6 (C-
20), 117.9 (C-5), 119.5 (C-60), 120.7 (C-50), 122.2
(C-10), 126.4 (C-6), 147.6 (C-30), 149.3 (C-200), 150.4
(C-40), 154.1 (C-9), 157.4 (C-7), 164.1 (C-2),
177.7(C@O). HRESIMS m/z [M++H] 295.0602, calcd
295.0606.
5.3.3. Analgesic activity. Test for analgesic activity was
performed by tail-flick technique14,15 using Wistar albi-
no mice (25–30 g) of either sex selected by random sam-
pling technique. Diclofenac sodium 20 mg/kg was
administered as a standard for comparison and test
compounds, extract at dose level of 25 mg/kg were
administered orally. The reaction time was recorded at
30, 60, 90, 120, 150 and 180 min after treatment, cut-
off time was 10 s. The percent analgesic activity was
calculated.
Compound 3: [Lophirone L] mp 262 ꢁC [a]D ꢀ6.4ꢁ (c 1;
EtOH) IR (KBr) mmax 3384, 2949, 1632, 1454, 1022,
631 cmꢀ1 1H NMR (200 MHz, Me2CO-d6) d 4.72
.
(1H, dd, J = 8 Hz, 2 Hz, H-a), 5.42 (1H, d, J = 8 Hz,
1.2 Hz, H-b), 6.08 (1H, d, J = 2 Hz, H-30), 6.10 (1H,
dd, J = 8 Hz, 2 Hz, H-50), 6.80 (2H, d, J = 8 Hz, H-3,
5), 7.38 (1H, d, J = 8 Hz, H-60), 7.40 (2H, d, J = 8 Hz,
H-2, 6), 12.50 (1H, s, –OH) 13C NMR (75 MHz,
Me2CO-d6) d 58.7 (C-a), 83.8 (C-b), 103.1 (C-30), 108.0
(C-50), 113.9 (C-10), 115.6 (C-3, 5), 128.6 (C-2, 6),
131.4 (C-1), 132.4 (C-60), 157.3 (C-4), 164.9 (C-20),
165.7 (C-40), 201.4 (C@O). HRESIMS m/z [M+ꢀH]
527.1341, calcd 527.1342.
Acknowledgment
The authors thank Dr. J. S. Yadav, Director, IICT, for
his encouragement and support during the course of this
work.
5.2. Synthetic procedures
References and notes
General procedure for the debenzylation of benzyl
ethers: To a solution of benzyl ether (1.0 g, 2.5 mmol)
in trigol was added iodine (0.46 g, 3.75 mmol) and re-
fluxed for 2 h at 120 ꢁC. After completion of the reac-
tion, the reaction mixture was treated with hypo
solution and extracted with ethyl acetate (3·50 ml),
dried and concentrated. The product obtained was puri-
fied using column chromatography. The fractions eluted
at 30% ethyl acetate in petroleum ether contained pure
hydroxy compound.
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