Concise synthesis of two trisaccharide analogs related to the glycone constituent of phanoside, a novel insulin releasing natural product

Article abstract of DOI:10.1016/j.tet.2007.04.089

Two trisaccharides (2 and 3) related to the glycone part of phanoside, an insulin release stimulator, have been synthesized in excellent yield.

Full text of DOI:10.1016/j.tet.2007.04.089

Tetrahedron 63 (2007) 7240–7245
Concise synthesis of two trisaccharide analogs related
to the glycone constituent of phanoside, a novel insulin
releasing natural product*
*
Geetanjali Agnihotri, Pintu Kumar Mandal and Anup Kumar Misra
Medicinal and Process Chemistry Division, Central Drug Research Institute, Chattar Manzil Palace, Lucknow 226001, UP, India
Received 15 February 2007; revised 6 April 2007; accepted 26 April 2007
Available online 3 May 2007
Abstract—Two trisaccharides (2 and 3) related to the glycone part of phanoside, an insulin release stimulator, have been synthesized in
excellent yield.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
potent than well known anti-diabetic drugs, such as sulfonyl-
ureas.4 As claimed in the original report, phanoside contains
a branched trisaccharide glycone consisting of D-glucose,
D-rhamnose, and D-lyxose.
Diabetes has been classified as insulin dependent (type 1)
and noninsulin dependent (type 2). Noninsulin dependent
(type 2) diabetes is the commonest form of diabetes consti-
tuting 90% of the diabetic population.1,2 Its prevalence in
more affluent societies is spectacular and of general con-
cern.3 It has broken the age barrier and also appears in youn-
ger people. Though its management through drugs is
possible, drugs come together with serious side effects.
Natural products can provide a better alternative as more
effective anti-diabetics with less side effects. Recently, it
has been reported that phanoside4 (1, Fig. 1), a natural prod-
uct isolated from the plant Gynostemma pentaphyllum is
effective in stimulating insulin release, and is much more
However, L-rhamnose is quite abundant in plant natural
products and D-rhamnose is occasionally found in the micro-
bial origin. Although the structural elucidation for the pres-
ence of D-rhamnose moiety instead of L-rhamnose was not
clearly stated in the original paper, we were interested in
synthesizing some analogous trisaccharide moieties related
to the glycone part of phanoside containing a L-rhamnose
moiety. Oligosaccharides containing D-lyxose are also
scarce in nature. In order to understand the role of the gly-
cone part of phanoside in enhancing the insulin release, it
is essential to have higher quantities of several trisaccharide
analogs related to the glycone part of phanoside. Hence it
was thought to develop a synthetic route for the synthesis
of two trisaccharide analogs (2 and 3) related to the glycone
part of phanoside.
OH
OH
OH
O
CH3
O
HO
OH
O
O
O
HO
OH
HO
HO
O
O
OH
OH
O
1
HO
2. Results and discussion
HO
H3C
OH
O
HO
O
HO
H3C
O
The synthesis of target trisaccharide (2) as its 4-methoxy-
phenyl glycoside is demonstrated in Scheme 1. Treatment
of D-lyxose tetraacetate (4) with 4-methoxy phenol in
the presence of trifluoromethanesulfonic acid afforded
4-methoxyphenyl glycoside (5). Compound 5 was converted
to compound 6 following a sequence of reactions consisting
of deacetylation using sodium methoxide,5 isopropylidena-
tion6 using 2,2-dimethoxypropane and p-toluenesulfonic
acid, and benzylation using benzyl bromide under phase
transfer conditions.7 Removal of the isopropylidene group8
from compound 6 using 80% aq acetic acid furnished com-
pound 7. Initially, a regioselective glycosylation strategy9
O
HO
OH
O HO
O
O
H3C
HO
O
OCH3
HO
HO
O
O
OH
O
OCH3
HO
OH
2
3
Figure 1. Structure of phanoside (1) and trisaccharide analogs of the
glycone (2 and 3).
*
C.D.R.I communication no. 7049.
Keywords: Carbohydrate; Glycosylations; Natural products; Insulin; Phano-
side.
* Corresponding author. Tel.: +91 522 2612411 18x4336; fax: +91 522
2623405; e-mail: akmisra69@rediffmail.com
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.04.089

G. Agnihotri et al. / Tetrahedron 63 (2007) 7240–7245
7241
OAc
O
OAc
OH
O
O
AcO
AcO
O
a
b
c
AcO
AcO
O
BnO
HO
BnO
O
OAc
4
5
OMP
7
6
OMP
OMP
OH
O
OAc
(i) Bu2SnO, CH3OH
(ii) Acetobromo-D-glucose
BnO
O
AcO
O
X
AcO
OH
O
Bu4NBr
OAc
OMP
8
BnO
HO
OAc
O
X
7
AcO
AcO
OMP
OCH3
OAc
OH
O
SEt
O
MP:
OAc
BnO
O
AcO
NIS-TfOH, CH2Cl2
O
O
AcO
OMP
OBn
9
d
SEt
O
H3C
BnO
OBn
O
BnO
BnO
BnO
H3C
BnO
H3C
OH
O
OBn
11
e
O
O
OBn
f
BnO
O
O
BzO
O
BnO
HO
BnO
BzO
OMP
10
OMP
h
OMP
OH
12
13
OBz
BnO
O
BnO
O
HO
BzO
BnO
HO
H3C
BzO
SPh
BzO
H3C
OBz
O
OBz
14
O
OH
O
O
BnO
O
g
O
O
HO
HO
HO
O
BzO
O
OBz
OH
OMP
15
OMP
2
Scheme 1. Reagents: (a) 4-(OCH3)–C6H5OH, TfOH, CH2Cl2, 2 h, 10 ꢀC, 90%; (b) (i) CH3ONa, CH3OH, rt, 3 h; (ii) 2,2-dimethoxypropane, p-toluenesulfonic
acid, DMF, 6 h, 71% in two steps; (iii) benzyl bromide, tetrabutylammonium iodide, 50% aq NaOH, CH2Cl2, rt, 3 h, 90%; (c) 80% aq AcOH, 60 ꢀC, 45 min,
93%; (d) (i) Bu2SnO, CH3OH, reflux, 6 h; (ii) benzoyl chloride, toluene, rt, 8 h, 80%; (e) N-iodosuccinimide, TfOH, CH2Cl2, ꢁ30 ꢀC, 45 min, 78%; (f) 0.1 M
CH3ONa, CH3OH, rt, 3 h, quantitative; (g) N-iodosuccinimide, TfOH, CH2Cl2, ꢁ30 ꢀC, 45 min, 72%; (h) (i) CH3ONa, CH3OH, rt, 12 h; (ii) H2, Pd(OH)2–C,
CH3OH, rt, 24 h, 61% in two steps.
was attempted to prepare disaccharide 8, through the forma-
tion of stannylidene acetal of compound 7, followed by treat-
ment with peracetylated glucosyl bromide. After several
trials, no disaccharide 8 could be isolated and starting mate-
rial was recovered. Another regioselective glycosylation was
carried out using ethyl 2,3,4,6-tetra-O-acetyl-1-thio-b-D-
glucopyranoside under N-iodosuccinimide–triflic acid pro-
moted glycosylation,10 but only some orthoester 9 could
be isolated instead of disaccharide 8. Following literature
reports,11 the rearrangement of orthoester 9 to the required
disaccharide 8 also failed and compound 7 was recovered.
It was then decided to selectively protect the 3-hydroxy
group of compound 7 with the 4-methoxybenzyl group via
stannylidene acetal formation. Unfortunately, a mixture of
products was isolated upon treatment of compound 7 with
dibutyltin oxide followed by treatment with 4-methoxy-
benzyl chloride. Finally, stannylidene acetal formation of
compound 7 followed by treatment with benzoyl chloride12
yielded selectively benzoyl protected D-lyxose derivative 10
in excellent yield. Glycosylation of compound 10 with ethyl
2,3,4-tri-O-benzyl-1-thio-a-L-rhamnopyranoside (11), pre-
pared from L-rhamnose in three steps, with N-iodosuccini-
mide and triflic acid10 afforded the disaccharide derivative
12. The presence of two anomeric signals at 97.4 (C-1)
and 97.0 (C-10) in the 13C NMR spectrum confirmed the for-
mation of 12. Following an earlier literature report,13 the
configuration of the L-rhamnosyl linkage of compound 12
was confirmed by the partially decoupled 13C NMR spec-
trum, in which the C-1/H-1 coupling constant (JC-1/H-1) for
L-rhamnosyl linkage was found to be 172.0 Hz indicating
the formation of a a-linkage. Removal of the benzoyl group
using sodium methoxide gave compound 13, which on
glycosylation with phenyl 2,3,4,6-tetra-O-benzoyl-a-D-glu-
copyranoside (14)14 using N-iodosuccinimide and trifluoro-
methanesulfonic acid furnished trisaccharide derivative 15.
The presence of three anomeric signals at 101.8 (C-100),
99.7 (C-1), and 97.4 (C-10) in the 13C NMR spectrum,
confirmed the formation of trisaccharide derivative 15.
SEt
OH
HO
OAc
H3C
AcO
O
AcO
AcO
H3C
HO
O
AcO
16
H3C
OH
O
O
OAc
b
O
BnO
HO
O
O
O
HO
BnO
a
O
O
OMP
7
H3C
AcO
O
H3C
HO
O
OCH3
OMP
O
AcO
OAc
HO
17
3
OH
Scheme 2. Reagents: (a) N-iodosuccinimide, TfOH, CH2Cl2, ꢁ30 ꢀC, 45 min, 68%; (b) (i) CH3ONa, CH3OH, rt, 12 h; (ii) H2, Pd(OH)2–C, CH3OH, rt, 10 h,
65% in two steps.

7242
G. Agnihotri et al. / Tetrahedron 63 (2007) 7240–7245
Conventional debenzoylation followed by hydrogenolysis15
of trisaccharide 15 afforded target trisaccharide 2 in 62%
yield.
3COCH3); 13C NMR (CDCl3, 75 Hz): d 169.5, 169.4,
169.3 (3COCH3), 155.4, 149.9, 117.9 (2C), 114.6 (2C),
96.8 (C-1), 69.5, 68.5, 66.8, 60.2 (C-5), 55.4 (OCH3), 20.7
(3C, COCH3); ESI-MS: m/z¼405.1 [M+Na]+. Anal. Calcd
for C18H22O9 (382.1): C, 56.54; H, 5.80. Found: C, 56.30;
H, 6.10.
In a separate experiment, another analogous trisaccharide 3
as its 4-methoxyphenyl glycoside was prepared follow-
ing Scheme 2. Glycosylation of compound 7 with ethyl
2,3,4-tri-O-acetyl-1-thio-a-L-rhamnopyranoside (16)16 using
N-iodosuccinimide and trifluoromethanesulfonic acid fur-
nished analogous trisaccharide derivative 17. Formation of
compound 17 was confirmed by 1H, 13C, and partially
decoupled 13C NMR spectra. Saponification followed by hy-
drogenolysis of trisaccharide 17 furnished the trisaccharide
3, which was confirmed by NMR and mass spectroscopies.
4.3. 4-Methoxyphenyl 4-O-benzyl-2,3-O-isopropylidene-
a-D-lyxopyranoside (6)
A solution of compound 5 (5.0 g, 13.1 mmol) in 0.05 M so-
dium methoxide in methanol (30.0 mL) was stirred at room
temperature for 3 h. The reaction mixture was neutralized
with Dowex 50W-X8 (H+), filtered, and the filtrate was evap-
orated to dryness to give a glassy solid in quantitative yield
(3.16 g). The dried mass thus obtained was dissolved in
anhydrous DMF (15 mL) and 2,2-dimethoxypropane
(2.4 mL, 18.5 mmol) was added to it followed by the addi-
tion of p-toluene sulfonic acid (w100 mg) to make the solu-
tion acidic (pHw2). After stirring at room temperature for
6 h, the reaction mixture was neutralized with triethylamine
and filtered through the Celite bed. The filtrate was evapo-
rated to dryness and the crude mass was purified over SiO2
using hexane–EtOAc (3:1) to afford pure 4-methoxyphenyl
2,3-O-isopropylidene-a-D-lyxopyranoside (2.77 g, 71%),
which was dissolved in CH2Cl2 (20 mL), and benzyl
bromide (1.6 mL, 14.0 mmol) followed by 50% aq KOH so-
lution (5 mL) and tetrabutylammonium iodide (w100 mg)
were added to it. After stirring at room temperature
for 3 h, the reaction mixture was diluted with CH2Cl2
(50 mL). The organic layer was washed successively with
water, aq NaCl, and water, dried (Na2SO4), and concentrated
under reduced pressure. Column chromatography of the
crude product over silica gel using hexane–EtOAc (5:1) fur-
nished pure compound 6 (3.25 g, 90%) as syrup; [a]2D5 +60.0
(c 1.2, CHCl3); IR (neat): 2359, 1597, 1375, 1225,
3. Conclusions
In summary, two trisaccharide analogs related to the glycone
constituent of phanoside, a novel insulin releasing natural
product have been synthesized as 4-methoxyphenyl glyco-
sides in a very concise manner.
4. Experimental
4.1. General procedure
All the reactions were monitored by thin layer chromato-
graphy over silica gel coated TLC plates. The spots on
TLC were visualized by warming ceric sulfate (2%
Ce(SO4)2 in 2 M H2SO4) sprayed plates on a hot plate. Silica
gel of 230–400 mesh was used for column chromatography.
1H and 13C NMR spectra were recorded on a Brucker Ad-
vance DPX 300 MHz using TMS as an internal reference.
Chemical shift values were expressed in d parts per million.
Elemental analysis was carried out on a Carlo ERBA-1108
analyzer. Optical rotations were measured at 25 ꢀC on a
Rudolf Autopol III polarimeter. Commercially available
grades of organic solvents of adequate purity are used in
many reactions.
1
1073 cmꢁ1; H NMR (CDCl3, 300 MHz): d 7.33–7.20 (m,
5H, ArH), 6.95–6.89 (m, 2H, ArH), 6.79–6.73 (m, 2H,
ArH), 5.42 (d, J¼1.5 Hz, 1H, 1-H), 4.72 (d, J¼12.0 Hz,
1H, CH2C6H5), 4.61 (d, J¼12.0 Hz, 1H, CH2C6H5), 4.34–
4.30 (m, 1H, 2-H), 4.27 (dd, J¼5.7 and 1.8 Hz, 1H, 3-H),
3.73 (s, 3H, OCH3), 3.63–3.60 (m, 3H, 4-H and 5-Ha,b),
1.45, 1.37 (2s, 6H, C(CH3)2); 13C NMR (CDCl3, 75 Hz):
d 155.1, 150.3, 138.2, 128.3 (2C), 127.8 (2C), 127.7, 117.8
(2C), 114.6 (2C), 109.3 (C(CH3)2), 97.0 (C-1), 77.5, 75.4
(PhCH2), 74.5, 71.9, 59.5 (C-5), 55.4 (OCH3), 28.1
(C(CH3)2), 26.5 (C(CH3)2); ESI-MS: m/z¼409.2 [M+Na]+.
Anal. Calcd for C22H26O6 (386.2): C, 68.38; H, 6.78. Found:
C, 68.20; H, 6.95.
4.2. 4-Methoxyphenyl 2,3,4-tri-O-acetyl-a-D-lyxo-
pyranoside (5)
To a solution of 1,2,3,4-tetra-O-acetyl-a-D-lyxopyranose (4,
6.0 g, 18.8 mmol) and 4-methoxy phenol (2.81 g,
22.6 mmol) in dry CH2Cl2 (25 mL) was added trifluoro-
methanesulfonic acid (150 mL) at 0 ꢀC and the reaction mix-
ture was allowed to stir at 10 ꢀC for 2 h. The reaction mixture
was diluted with CH2Cl2 and the organic layer was washed
successively with water, aq NaHCO3, and water, dried
(Na2SO4), and concentrated under reduced pressure. Purifi-
cation of the crude reaction product by column chromato-
graphy on silica gel using hexane–EtOAc (4:1) furnished
pure compound 5 (6.5 g, 90%) as thick syrup; [a]2D5 +31.1
(c 1.2, CHCl3); IR (neat): 1715, 1509, 1372, 1222, 1044,
4.4. 4-Methoxyphenyl 4-O-benzyl-a-D-lyxo-
pyranoside (7)
Compound 6 (3.0 g, 7.77 mmol) was dissolved in 80% aq
acetic acid (25 mL) and the reaction mixture was stirred at
60 ꢀC for 45 min. The reaction mixture was evaporated
and co-evaporated with toluene under reduced pressure.
Purification of the crude reaction product using a short pad
of SiO2 using hexane–EtOAc (3:1) as the eluant furnished
compound 7 (2.5 g, 93%) as yellow syrup; [a]2D5 +50.2 (c
1.2, CHCl3); IR (neat): 2927, 2368, 2595, 1352, 1029,
1
831 cmꢁ1; H NMR (CDCl3, 300 MHz): d 7.00–6.96 (m,
2H, ArH), 6.83–6.73 (m, 2H, ArH), 5.50 (dd, J¼9.9 and
3.6 Hz, 1H, 3-H), 5.39 (dd, J¼3.3 and 2.4 Hz each, 1H,
2-H), 5.30 (d, J¼2.4 Hz, 1H, 1-H), 5.27–5.19 (m, 1H,
4-H), 3.90 (dd, J¼11.1 and 5.7 Hz, 1H, 5-Ha), 3.77 (s, 3H,
OCH3), 3.76–3.71 (m, 1H, 5-Hb), 2.18, 2.04 (2s, 9H,
673 cmꢁ1
;
1H NMR (CDCl3, 300 MHz): d 7.31–7.25
(m, 5H, ArH), 6.93 (d, J¼9.0 Hz, 2H, ArH), 6.77 (d,

G. Agnihotri et al. / Tetrahedron 63 (2007) 7240–7245
7243
J¼9.0 Hz, 2H, ArH), 5.30 (br s, 1H, 1-H), 4.64–4.60 (m, 2H,
CH2Ph), 4.09–4.07 (m, 2H, 2-H and 3-H), 3.75 (s, 3H,
OCH3), 3.80–3.62 (m, 3H, 4-H and 5-Ha,b); 13C NMR
(CDCl3, 75 Hz): d 155.1, 150.4, 137.9, 128.6 (2C), 127.8
(3C), 117.8 (2C), 114.6 (2C), 98.6 (C-1), 75.3, 72.5
(PhCH2), 70.5, 70.3, 61.0 (C-5), 55.5 (OCH3); ESI-MS:
m/z¼369.1 [M+Na]+. Anal. Calcd for C19H22O6 (346.1):
C, 65.88; H, 6.40. Found: C, 65.70; H, 6.62.
J¼12.3 Hz, 1H, CH2Ph), 4.69–4.60 (m, 5H, 2CH2Ph,
10-H), 4.58 (d, J¼12.6 Hz, 1H, CH2Ph), 4.53 (d, J¼
11.0 Hz, 1H, CH2Ph), 4.33–4.28 (m, 1H, 2-H), 4.0–3.92
(m, 1H, 50-H), 3.88 (s, 3H, OCH3), 3.86–3.84 (m, 2H,
5-Ha,b), 3.83 (t, J¼4.5 and 4.5 Hz, 1H, 20-H), 3.81–3.78
(m, 1H, 4-H), 3.76 (dd, J¼9.0 and 3.1 Hz, 1H, 30-H), 3.51
(t, J¼9.3 and 9.3 Hz, 1H, 40-H), 0.98 (d, J¼6.3 Hz, 3H,
CH3); 13C NMR (CDCl3, 75 Hz): d 165.5 (COPh), 154.4,
151.1, 139.3–114.9 (Ar C), 97.4 (C-1), 97.0 (C-10), 80.6,
80.0, 75.7, 75.3 (CH2Ph), 73.7 (CH2Ph), 73.2 (CH2Ph),
72.8 (CH2Ph), 72.7, 72.3 (2C), 68.9, 62.3 (C-5), 57.0
(OCH3), 17.8 (CH3); ESI-MS: m/z 889.5 [M+Na]+. Anal.
Calcd for C53H54O11 (866.3): C, 73.42; H, 6.28. Found: C,
73.25; H, 6.50.
4.5. 4-Methoxyphenyl 3-O-benzoyl-4-O-benzyl-a-D-
lyxopyranoside (10)
A solution of compound 7 (2.5 g, 7.22 mmol) and dibutyltin
oxide (2.16 g, 8.67 mmol) in anhydrous methanol (20 mL)
was refluxed for 3 h. The reaction mixture was concentrated
and co-evaporated with toluene several times. The dried
mass was redissolved in dry toluene and benzoyl chloride
(930 mL, 7.92 mmol) was added to it, and the reaction mix-
ture was allowed to stir at room temperature for 8 h. The
reaction was quenched by the addition of methanol and the
reaction mixture was concentrated. Column chromato-
graphy of the crude product over silica gel using hexane–
EtOAc (4:1) furnished pure compound 10 (2.6 g, 80%) as
glassy solid; [a]2D5 +40.8 (c 1.2, CHCl3); IR (KBr): 2938,
4.7. 4-Methoxyphenyl 2,3,4-tri-O-benzyl-a-L-rhamno-
pyranosyl-(1/2)-4-O-benzyl-a-D-lyxopyranoside (13)
A solution of compound 12 (1.5 g, 1.73 mmol) in 0.1 M so-
dium methoxide in methanol (10.0 mL) was stirred at room
temperature for 3 h. The reaction mixture was neutralized
with Dowex 50W-X8 (H+), filtered, and the filtrate was evap-
orated to dryness to give disaccharide derivative 13 as syrup
(1.31 g); [a]2D5 ꢁ16.0 (c 1.2, CHCl3); IR (neat): 2926, 2369,
1592, 1351 cmꢁ1; 1H NMR (CDCl3, 300 MHz): d 7.32–7.18
(m, 20H, ArH), 6.89 (d, J¼9.0 Hz, 2H, ArH), 6.76 (d,
J¼9.0 Hz, 2H, ArH), 5.05 (d, J¼3.8 Hz, 1H, 3-H), 4.93
(br s, 1H, 1-H), 4.90 (d, J¼11.1 Hz, 1H, CH2Ph), 4.74–
4.59 (m, 8H, 4CH2Ph, 10-H), 4.08–4.01 (m, 1H, 50-H),
4.0–3.96 (m, 1H, 2-H), 3.86–3.80 (m, 2H, 20-H and 4-H),
3.76 (s, 3H, OCH3), 3.75 (dd, J¼9.0 and 2.7 Hz, 1H,
30-H), 3.68–3.56 (m, 3H, 5-Ha,b and 40-H), 1.32 (d,
J¼6.0 Hz, 3H, CH3); 13C NMR (CDCl3, 75 Hz): d 155.2–
127.7 (Ar C), 117.9 (2C), 114.5 (2C), 98.5 (C-1), 97.8
(C-10), 80.3, 79.4, 76.1, 75.4 (2C, CH2Ph), 75.2 (CH2Ph),
72.9 (CH2Ph), 72.4, 72.3, 70.2, 69.1, 61.8 (C-5), 55.4
(OCH3), 18.1 (CH3); ESI-MS: m/z 785.3 [M+Na]+. Anal.
Calcd for C46H50O10 (762.3): C, 72.42; H, 6.61. Found: C,
72.25; H, 6.80.
1
2365, 1695, 1594, 1286, 1093, 1006, 705 cmꢁ1; H NMR
(CDCl3, 300 MHz): d 8.08–8.05 (m, 2H, ArH), 7.61–7.56
(m, 1H, ArH), 7.48–7.43 (m, 2H, ArH), 7.28–7.14 (m, 5H,
ArH), 7.02 (d, J¼8.7 Hz, 2H, ArH), 6.82 (d, J¼8.4 Hz,
2H, ArH), 5.64 (dd, J¼8.1 and 3.0 Hz, 1H, 3-H), 5.34 (d,
J¼3.0 Hz, 1H, 1-H), 4.65 (s, 2H, CH2Ph), 4.34 (t, J¼2.7
and 2.7 Hz, 1H, 2-H), 4.09–4.02 (ddd, J¼8.1, 5.4, and
2.7 Hz, 1H, 4-H), 3.90–3.82 (m, 2H, 5-Hab), 3.78 (s, 3H,
OCH3); 13C NMR (CDCl3, 75 Hz): d 165.4 (COPh), 155.1,
150.2, 137.9, 133.2 (2C), 129.9, 129.8 (2C), 128.4 (2C),
128.3 (2C), 127.8, 127.7, 117.9 (2C), 114.5 (2C), 98.9
(C-1), 73.3, 72.6, 72.3, 69.0, 61.8 (C-5), 55.4 (OCH3);
ESI-MS: m/z¼473.2 [M+Na]+. Anal. Calcd for C26H26O7
(450.1): C, 69.32; H, 5.82. Found: C, 69.14; H, 6.04.
4.6. 4-Methoxyphenyl 2,3,4-tri-O-benzyl-a-L-rhamno-
pyranosyl-(1/2)-3-O-benzoyl-4-O-benzyl-a-D-lyxo-
pyranoside (12)
4.8. 4-Methoxyphenyl [2,3,4-tri-O-benzyl-a-L-rhamno-
pyranosyl-(1/2)]-[2,3,4,6-tetra-O-benzoyl-b-D-gluco-
pyranosyl-(1/3)]-4-O-benzyl-a-D-lyxopyranoside (15)
To a solution of compound 10 (1.0 g, 2.22 mmol) and com-
pound 11 (1.3 g, 2.66 mmol) in anhydrous CH2Cl2 (15 mL)
To a solution of compound 13 (1.0 g, 1.31 mmol) and phenyl
2,3,4,6-tetra-O-benzoyl-1-thio-b-D-glucopyranoside (14,
1.1 g, 1.6 mmol) in anhydrous CH2Cl2 (10 mL) was added
˚
was added powdered MS (4 A, 2.0 g) and the mixture was
stirred under argon for 1 h. N-Iodosuccinimide (658 mg,
2.92 mmol) was added to the reaction mixture and cooled to
ꢁ30 ꢀC. Trifluoromethanesulfonic acid (25 mL, 0.29 mmol)
was added to the reaction mixture at ꢁ30 ꢀC and the reaction
mixture was allowed to stir for 30 min at ꢁ30 ꢀC. The reac-
tion mixture was filtered through a Celite bed and the organic
layer was washed with 5% aq Na2S2O3, satd NaHCO3, and
water in succession, dried (Na2SO4), and concentrated to a
syrupy product. Column chromatography of the crude prod-
uct over SiO2 using hexane–EtOAc (7:1) afforded pure
disaccharide derivative 12 (1.5 g, 78%) as syrup; [a]D25
ꢁ27.1 (c 1.2, CHCl3); IR (neat): 2367, 1595, 1351,
˚
powdered MS (4 A, 1.5 g) and the mixture was stirred under
argon for 1 h. N-Iodosuccinimide (390 mg, 1.73 mmol) was
added to the reaction mixture and cooled to ꢁ30 ꢀC. Tri-
fluoromethanesulfonic acid (15 mL, 0.17 mmol) was added
to the reaction mixture at ꢁ30 ꢀC and the reaction mixture
was allowed to stir for 30 min at ꢁ30 ꢀC. After completion
of the reaction, the reaction mixture was filtered through a
Celite bed and the organic layer was washed with 5% aq
Na2S2O3, satd NaHCO3, and water, dried (Na2SO4), and
concentrated to a syrupy mass. Column chromatography
of the crude product over SiO2 using hexane–EtOAc (5:1)
afforded pure trisaccharide derivative 15 (1.26 g, 72%);
[a]2D5 +10.6 (c 1.2, CHCl3); IR (neat): 2924, 2368, 1595,
1
1057 cmꢁ1; H NMR (CDCl3, 300 MHz): d 8.06–8.03 (m,
2H, ArH), 7.54–7.50 (m, 1H, ArH), 7.35–7.25 (m, 22H,
ArH), 7.02–6.96 (m, 2H, ArH), 6.78 (d, J¼9.0 Hz, 2H,
ArH), 5.62 (dd, J¼8.4 and 3.0 Hz, 1H, 3-H), 4.96 (br s,
1H, 1-H), 4.90 (d, J¼11.1 Hz, 1H, CH2Ph), 4.79 (d,
1351, 1097, 708 cmꢁ1 1H NMR (CDCl3, 300 MHz):
;
d 8.10–8.04 (m, 2H, ArH), 7.85–7.80 (m, 4H, ArH), 7.74–
7.71 (m, 2H, ArH), 7.52–7.46 (m, 4H, ArH), 7.42–7.22

7244
G. Agnihotri et al. / Tetrahedron 63 (2007) 7240–7245
(m, 22H, ArH), 7.20–7.07 (m, 4H, ArH), 6.91–6.86 (m, 2H,
ArH) 6.57 (d, J¼9.0 Hz, 2H, ArH), 6.46 (d, J¼8.7 Hz, 2H,
ArH), 5.88 (t, J¼9.6, 9.6 Hz, 1H, 300-H), 5.62 (t, J¼9.6
and 9.6 Hz, 1H, 200-H), 5.42 (t, J¼9.6 and 9.6 Hz, 1H,
400-H), 5.34 (d, J¼8.1 Hz, 1H, 100-H), 5.25 (br s, 1H, 1-H),
5.05 (d, J¼11.1 Hz, 1H, CH2Ph), 4.82–4.70 (m, 4H,
2CH2Ph, 3-H), 4.66 (br s, 1H, 10-H), 4.61 (d, J¼11.6 Hz,
1H, CH2Ph), 4.56–4.51 (m, 3H, CH2Ph), 4.39 (t, J¼3.6
and 3.6 Hz, 1H, 2-H), 4.30 (dd, J¼12.0 and 5.1 Hz, 1H,
600-Ha), 4.17–4.10 (m, 2H, 600-Hb and 50-H), 3.92 (dd,
J¼9.0 and 2.7 Hz, 1H, 30-H), 3.84–3.82 (m, 2H, 500-H and
20-H), 3.81–3.77 (m, 1H, 4-H), 3.76 (s, 3H, OCH3), 3.75–
3.73 (m, 2H, 5-Ha,b), 3.72–3.68 (m, 1H, 40-H), 1.42 (d,
J¼6.0 Hz, 3H, CH3); 13C NMR (CDCl3, 75 Hz): d 165.7,
165.6, 164.9, 164.8 (4COPh), 138.8–114.3 (Ar C), 101.0
(C-100), 99.5 (C-1), 98.7 (C-10), 80.9, 80.5, 75.7, 75.4, 74.7,
73.4, 72.7 (2C), 72.6 (2C, CH2Ph), 72.5, 71.2 (2C,
CH2Ph), 69.4 (2C), 63.2 (C-600), 62.6 (C-5), 55.4 (OCH3),
18.5 (CH3); ESI-MS: m/z 1363.5 [M+Na]+. Anal. Calcd
for C80H76O19 (1340.5): C, 71.63; H, 5.71. Found: C,
71.45; H, 5.98.
was added to the reaction mixture and it was cooled to
ꢁ30 ꢀC. Trifluoromethanesulfonic acid (35 mL, 0.39 mmol)
was added and the reaction mixture was allowed to stir
for 30 min at ꢁ30 ꢀC. After completion of the reaction,
the reaction mixture was filtered through a Celite bed and
the filtrate was washed with 5% aq Na2S2O3, satd NaHCO3,
and water, dried (Na2SO4), and concentrated to a syrupy
product. Column chromatography of the crude product
over SiO2 using hexane–EtOAc (3:1) afforded pure trisac-
charide derivative 17 (872 mg, 68%); [a]2D5 ꢁ26.1 (c 1.2,
CHCl3); IR (neat): 2935, 2366, 1752, 1594, 1375, 1225,
1
1047 cmꢁ1; H NMR (CDCl3, 300 MHz): d 7.28–7.14 (m,
5H, ArH), 6.97 (d, J¼8.7 Hz, 2H, ArH), 6.78 (d, J¼
9.0 Hz, 2H, ArH), 5.35–5.24 (m, 5H, 1-H, 10-H, 20-H,
30-H, and 40-H), 5.13–4.97 (m, 6H, 100-H, 200-H, 300-H,
400-H, CH2Ph), 4.20–4.09 (m, 4H, 50-H, 500-H, 2-H, 3-H),
4.04–3.87 (m, 2H, 5-Ha,b), 3.77 (s, 3H, OCH3), 3.67–3.60
(m, 1H, 4-H), 2.18, 2.17, 2.16, 2.07, 2.06, 2.05 (6s, 18H,
6COCH3), 1.22–1.24 (m, 6H, 2CH3); 13C NMR (CDCl3,
75 Hz): d 169.9, 169.7, 169.5, 169.4, 169.3, 169.2
(6COCH3), 155.1–114.4 (Ar C), 98.5 (C-1), 97.3 (C-10 and
C-100), 71.2, 70.6, 70.5 (2C), 70.2 (CH2Ph), 69.8, 69.5,
69.1, 68.8, 68.7, 68.5, 67.1, 66.6 (C-5), 55.3 (OCH3), 20.6
(2C, 2COCH3), 20.5 (2C, 2COCH3), 20.3 (2C, 2COCH3),
17.3, 17.0 (2CH3); ESI-MS: m/z 913.3 [M+Na]+. Anal.
Calcd for C43H54O20 (890.3): C, 57.97; H, 6.11. Found: C,
57.75; H, 6.30.
4.9. 4-Methoxyphenyl [a-L-rhamnopyranosyl-(1/2)]-
[b-D-glucopyranosyl-(1/3)]-a-D-lyxopyranoside (2)
A solution of compound 15 (1.0 g, 0.75 mmol) in 0.1 M so-
dium methoxide in methanol (25.0 mL) was stirred at room
temperature for 12 h. The reaction mixture was neutralized
with Dowex 50W-X8 (H+), filtered, and the filtrate was evap-
orated to dryness to give a syrup, which was purified through
Sephadex LH-20 using toluene as eluant to give 4-methoxy-
phenyl [2,3,4-tri-O-benzyl-a-L-rhamnopyranosyl-(1/2)]-[b-
D-glucopyranosyl-(1/3)]-4-O-benzyl-a-D-lyxopyranoside,
which was dissolved in methanol (5 mL), and 20%
Pd(OH)2–C (300 mg) was added to it. The reaction mixture
was stirred under hydrogen at room temperature for 18 h.
The mixture was filtered through a Celite bed and concen-
trated to give target trisaccharide 2 (260 mg, 61%) as syrup;
[a]2D5 +22 (c 1.2, CH3OH); 1H NMR (CD3OD–D2O,
300 MHz): d 6.92–6.89 (m, 2H, ArH), 6.77–6.73 (m, 2H,
ArH), 5.28 (d, J¼4.8 Hz, 1H, 10-H), 4.96 (br s, 1H, 1-H),
4.47 (d, J¼7.8 Hz, 1H, 100-H), 4.10–4.03 (m, 2H, 20-H and
30-H), 3.88–3.86 (m, 1H, 40-H), 3.84–3.83 (m, 1H, 2-H),
3.82–3.77 (m, 3H, 600-Ha,b and 400-H), 3.64 (s, 3H, OCH3),
3.59–3.53 (m, 2H, 3-H and 50-H), 3.35–3.27 (m, 2H, 300-H
and 4-H), 3.25–3.20 (m, 3H, 500-H and 5-Ha,b), 3.17–3.14
(m, 1H, 200-H), 1.22 (d, J¼6.3 Hz, 3H, CH3); 13C NMR
(CD3OD–D2O, 75 Hz): d 154.0, 149.6, 116.4 (2C), 112.9
(2C), 101.8 (C-100), 99.7 (C-1), 97.4 (C-10), 77.1 (2C), 75.4
(2C), 75.0, 72.4 (2C), 71.2, 69.7, 69.4, 67.9, 60.0 (2C, C-5
and C-600), 53.4 (OCH3), 15.3 (CH3); ESI-MS: m/z 587.2
[M+Na]+. Anal. Calcd for C24H36O15 (564.2): C, 51.06; H,
6.43. Found: C, 50.85; H, 6.65.
4.11. 4-Methoxyphenyl [a-L-rhamnopyranosyl-(1/2)]-
[a-L-rhamnopyranosyl-(1/3)]-a-D-lyxopyranoside (3)
To a solution of compound 17 (800 mg, 0.9 mmol) in meth-
anol was added 20% Pd(OH)2–C (100 mg) and the reaction
mixture was stirred under hydrogen at room temperature
for 10 h. The mixture was filtered through Celite bed and
concentrated to give yellow syrup, which was dissolved in
0.1 M sodium methoxide in methanol (15.0 mL) and the re-
action mixture was stirred at room temperature for 12 h. The
reaction mixture was neutralized with Dowex 50W-X8 (H+),
filtered, and the filtrate was evaporated to dryness to give
a syrup, which was purified through Sephadex LH-20 using
80% aq EtOH as eluant to give pure trisaccharide 3 (320 mg,
1
65%) as a viscous liquid; [a]2D5 ꢁ10 (c 1.2, CH3OH); H
NMR (CD3OD–D2O, 300 MHz): d 6.92 (d, J¼8.7 Hz, 2H,
ArH), 6.76 (d, J¼9.0 Hz, 2H, ArH), 5.15 (br s, 1H, 1-H),
5.04 (d, J¼2.6 Hz, 2H, 10-H and 100-H), 4.09–4.08 (m, 1H,
20-H), 3.99–3.98 (m, 1H, 200-H), 3.86–3.74 (m, 3H, 30-H,
300-H, and 2-H), 3.73–3.55 (m, 4H, 40-H, 400-H, 3-H, and
4-H), 3.65 (s, 3H, OCH3), 3.39–3.29 (m, 4H, 50-H, 500-H,
and 5-Ha,b), 1.23–1.13 (m, 6H, 2CH3); 13C NMR
(CD3OD–D2O, 75 MHz): 156.7, 149.1, 119.1 (2C), 115.6
(2C), 100.1 (2C, C-10 and C-100), 94.5 (C-1), 73.8 (2C),
73.7 (2C), 72.2, 72.1 (2C), 72.0 (2C), 70.5, 70.4, 68.8
(C-5), 56.1 (OCH3), 18.1, 17.9 (2CH3); ESI-MS: m/z 571.2
[M+Na]+. Anal. Calcd for C24H36O14 (548.2): C, 52.55; H,
6.62. Found: C, 52.38; H, 6.85.
4.10. 4-Methoxyphenyl [2,3,4-tri-O-acetyl-a-L-rhamno-
pyranosyl-(1/2)]-[2,3,4-tri-O-acetyl-a-L-rhamnopyr-
anosyl-(1/3)]-4-O-benzyl-a-D-lyxopyranoside (17)
To a solution of compound 7 (500 mg, 1.44 mmol) and
ethyl 2,3,4-tri-O-acetyl-a-L-rhamnopyranoside (16, 1.2 g,
3.60 mmol) in anhydrous CH2Cl2 (10 mL) was added pow-
dered MS (4 A, 1.0 g) and the mixture was stirred under
argon for 1 h. N-Iodosuccinimide (890 mg, 3.97 mmol)
Acknowledgements
Instrumentation facilities from SAIF, CDRI are gratefully
acknowledged. G.A. and P.K.M. thank CSIR, New Delhi
for providing a Senior and Junior Research Fellowships,
˚

G. Agnihotri et al. / Tetrahedron 63 (2007) 7240–7245
7245
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respectively. This project was partly funded by Department
of Science and Technology (DST), New Delhi (Project no.
SR/FTP/CSA-10/2002), India.
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