Synthesis of peracetylated chacotriose

Article abstract of DOI:10.1016/S0008-6215(01)00193-8

Steroidal glycoalkaloids of many Solanum species have recognized biological activities, especially those containing the glycosyl moiety α-L-rhamnopyranosyl-(1 → 2)-[α-L-rhamnopyranosyl-(1 → 4)]-D-glucopyranose (chacotriose) whose peracetate is here synthe

Full text of DOI:10.1016/S0008-6215(01)00193-8

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Carbohydrate Research 334 (2001) 281–287
Synthesis of peracetylated chacotriose
Marielba Morillo,a Vincent Lequart,b Eric Grand,b Ge´rard Goethals,b
Alfredo Usubillaga,a Pierre Villa,b Patrick Martinb,*
aInstituto de In6estigaciones, Facultad de Farmacia, Uni6ersidad de Los Andes, Me´rida 5101, Venezuela
bLaboratoire de Chimie Organique et Cine´tique, Uni6ersite´ de Picardie Jules Verne, 33 rue Saint-Leu,
F-80039 Amiens, France
Received 6 February 2001; accepted 4 July 2001
Abstract
Steroidal glycoalkaloids of many Solanum species have recognized biological activities, especially those containing
the glycosyl moiety a-
L
-rhamnopyranosyl-(1“2)-[a-
L
-rhamnopyranosyl-(1“4)]-D-glucopyranose (chacotriose)
whose peracetate is here synthesized and characterized by complete H and 13C NMR assignment. © 2001 Elsevier
1
Science Ltd. All rights reserved.
Keywords: Solanum; Glycoalkaloid; Chacotriose; L-Rhamnose
1. Introduction
Inactivation of Herpes simplex virus by
Solanum glycoalkaloids has been reported by
Thorne et al.7 who demonstrated that a-
chaconine, the glycoside of solanidine with
chacotriose, was the most effective, whereas
the corresponding aglycone was inactive. The
low activity of the aglycones indicates that the
role of the carbohydrate moiety is very impor-
tant. The biological activity of Solanum gly-
coalkaloids is believed to depend on the
interaction of the carbohydrate moiety with
membrane sugar receptors, which allow pene-
tration of the steroidal alkaloid and subse-
quent disruption of the cell metabolism of the
pathogen.8 Solanum americanum Miller is a
herbaceous plant that grows abundantly in
Venezuela.9 The expressed fruits and leaves of
this plant, commonly called ‘yerbamora’, are
used by the rural population to treat skin
injuries caused by Herpes zoster. The main
steroidal glycoalkaloids in the fruits of this
plant are a-solamargine and a-solasonine.10
Steroidal glycoalkaloids1 are secondary
metabolites frequently found in species of
Solanum, conferring on them resistance to in-
sects and other pests.2,3 Most Solanum species
contain two major glycoalkaloids which share
the same aglycone, bound either to
chacotriose, a-
-rhamnopyranosyl-(1“4)]-b-
ose, or solatriose, a- -rhamnopyranosyl-
(1“2)-[b- -glucopyranosyl-(1“3)]-b- -gal-
L
-rhamnopyranosyl-(1“2)-[a-
L
D
-glucopyran-
L
D
D
actopyranose. It has been demonstrated that
Solanum steroidal glycoalkaloids have anti-
neoplasic,4 antifungal,5 as well as trypanolytic
and trypanocidal activities.6 Glycosides con-
taining chacotriose are consistently more ac-
tive than their solatriose containing
counterparts.
* Corresponding author. Fax: +33-3-22827568.
E-mail address: patrick.martin@sc.u-picardie.fr (P. Mar-
tin).
0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(01)00193-8

282
M. Morillo et al. / Carbohydrate Research 334 (2001) 281–287
lidene-a- -glucofuranose (5) in 76% yield; the
D
Clinical tests carried out with a hydrophilic
cream containing either a crude extract of S.
americanum fruits or a-solamargine, applied
topically, healed patients suffering from H.
zoster, H. simplex, and H. genitalis after 3–10
days.11
formation of the anhydro group was ascer-
tained by signals at 46.9 ppm (C-6) and 48.1
13
ppm (C-5) in the C NMR spectrum. 3,6-Di-
O-benzyl-1,2-O-isopropylidene-a- -glucofur-
D
anose (7) was prepared by condensing
compound 5 with benzyl alcohol (5 equiv) in
the presence of KOH (6 equiv) in 1:1 toluene–
Me2SO; to facilitate its extraction, the crude
product was acetylated to separate the corre-
sponding 5-O-acetyl derivative 6 (76% yield)
which treated with NaOMe in MeOH gives
pure compound 7. Subsequently, 7 was treated
with 9:1 CF3CO2OH–water14 and the crude
product purified on silica gel to give 3,6-di-O-
Glycoalkaloids containing chacotriose are
known to be the most active of such alkaloids,
and such compounds as a-chaconine and a-so-
lamargine are not easily obtained in large
quantities. Since the glycosidic moiety,
chacotriose, is important for biological activ-
ity, it was decided to make it more readily
available by chemical synthesis as its perac-
etate. Peracetylated chacotriose is more stable
than unprotected chacotriose and it could be
readily transformed into a-chaconine or a-so-
lamargine on a commercial scale for inclusion
into antiviral creams, which could prove
cheaper alternatives to antiviral drugs already
on the market. Moreover, chacotriose could
be bound to other aglycones in the search for
new biologically active glycosides, or be ob-
tained as labeled derivatives which could be
used to study its mechanism of action in bio-
logical systems.
benzyl- -glucopyranose (8) in 86% yield; the
D
13C NMR spectrum showed signals at 92.8
ppm (C-1a) and 97.1 ppm (C-1b) which indi-
cated that the anomeric hydroxyl was free.
Acetylation of 8 gave 1,2,4-tri-O-acetyl-3,6-di-
O-benzyl- -glucopyranose (9) in 86% yield.
D
To obtain glucose in the required protected
form for attachment of two rhamnose units at
the 2- and 4-hydroxyl groups, 9 was initially
benzylated at the anomeric position by reac-
tion with benzyl alcohol in dry CH2Cl2 in the
15
presence of SnCl4 to give benzyl 2,4-di-O-
acetyl-3,6-di-O-benzyl-b- -glucopyranoside
D
13
2. Results and discussion
(10) as the sole anomer in 60% yield. The C
NMR spectrum of 10 showed the signal of the
anomeric carbon at 99.9 ppm (C-1b). Com-
pound 10 was then treated with NaOMe in
Peracetylated chacotriose was synthesized
starting from
D
-glucose. The strategy adopted
was to partially protect the glucose leaving
only the 2- and 4-hydroxyl groups available
MeOH to give benzyl 3,6-di-O-benzyl-b- -
D
glucopyranoside (11) in 98% yield without
13
for glycosidic bond formation with two
rhamnopyranose units. The synthetic sequence
started from 1,2:5,6-di-O-isopropylidene-a-
glucofuranose12 (1). 3-O-Benzyl-1,2-O-iso-
L
-
purification. The C NMR data of 11 showed
a signal for the anomeric carbon at 102.1
D
-
ppm. The intermediate 11 was thus obtained
from 1,2:5,6-di-O-isopropylidene-a- -gluco-
D
propylidene-a-
D
-glucofuranose (3) was pre-
furanose in an overall yield of 14%.
pared by the procedure of Goueth et al.13 in
two steps from 1 in 62% yield. Compound 3
was treated with p-toluenesulfonyl chloride in
1:1 toluene–C5H5N at 4 °C to give 3-O-ben-
L
-Rhamnose was first peracetylated with
Ac2O–C5H5N to give, after silica-gel chro-
matography, 1,2,3,4-tetra-O-acetyl- -rhamno-
L
pyranose (12) in 67% yield. The anomeric
carbon of 12 appeared at 90.3 (C-1b) and 90.6
zyl-1,2-O-isopropylidene-6-O-tosyl-a- -gluco-
D
13
furanose (4) in 90% yield; the presence of the
tosyl group at C-6 was confirmed in the 13C
NMR spectrum by the characteristic aryl sig-
nals. Compound 4 was treated with 2.2 equiv-
alents of NaOH13 in 9:1 dioxane–water and
the crude product was purified on silica gel to
give 5,6-anhydro-3-O-benzyl-1,2-O-isopropy-
ppm (C-1a) in the C NMR spectrum. Com-
pound 12 was treated with 4.5 equivalents of
HBr (33% in glacial acetic acid)16,17 to obtain
2,3,4-tri-O-acetyl-a- -rhamnopyranosyl bro-
L
mide (13) in 94% yield; the anomeric
carbon appeared at 83.7 ppm in 13C
NMR. Compound 11 was mixed with four

M. Morillo et al. / Carbohydrate Research 334 (2001) 281–287
283
equivalents of 13 in dry CH2Cl2 at 0 °C, in the
presence of tetramethylurea and silver trifl-
ate.18–20 The product was purified on silica gel
were measured with a JASCO digital polar-
imeter model DIP-370 using a sodium lamp at
25 °C. NMR spectra were recorded with a
Bruker WB-300 instrument for solutions in
CDCl3 (internal Me4Si). All compounds were
characterized by acquisition of 1H, 13C,
to give benzyl 2,3,4-tri-O-acetyl-a-
pyranosyl-(1“4)-3,6-di-O-benzyl-b-
pyranoside (14) (30%) and benzyl 2,3,4-tri-O-
acetyl-a- -rhamnopyranosyl-(1“2)-[(2,3,4-tri-
O-acetyl-a- -rhamnopyranosyl-(1“4)]-3,6-
di-O-benzyl-b- -glucopyranoside (15) (65%).
L
-rhamno-
D
-gluco-
DEPT, H–1H COSY, and H–13C correlated
experiments. Electron (EI-MS) and fast-atom
bombardment (FAB-MS) ionizations were ac-
complished on an AutoSpec (Micromass,
UK), high-resolution mass spectrometer. Elec-
trospray ionization (ESI-MS) was performed
on a SSQ710 (ThermoFinnigan, USA), simple
quadrupole mass spectrometer. For the posi-
tive ESI-MS experiments, the compound was
dissolved in 100:400:0.02 water–MeOH–
CH3CO2NH4 at a concentration of 0.02 mg
mL−1 and then introduced into the ion source
(Analytica of Branford, USA) at a flow rate of
3 mL min−1. Reactions were monitored by
either high-performance liquid chromatogra-
phy (HPLC) (Waters 721) using reverse-phase
column RP-18 (E. Merck), or CPG (Girdel)
with OV-17 columns. Analytical thin-layer
chromatography (TLC) was performed on E.
Merck aluminum-backed silica gel (Silica Gel
F254). Column chromatography was per-
formed on silica gel (60 mesh, Matrex) by
gradient elution with hexane–acetone or hex-
ane–EtOAc (in each case the ratio of silica gel
to product mixture to be purified was 30:1).
3-O-Benzyl-1,2-O-isopropylidene-6-O-tosyl-
1
1
L
L
D
The 13C NMR spectrum of 15 showed three
anomeric carbons at 97.2, 97.7, and 100.3
ppm, while the spectrum of 14 showed only
two at 97.4 and 98.6 ppm. A HMQC experi-
ment indicated a correlation between C-1 of
the rhamnose unit and H-4 of the glucose unit
indicating (1“4) glycosylation in 14. Com-
pound 15 was subjected to catalytic hy-
drogenolysis to remove the benzyl protecting
groups and subsequently acetylated to obtain
the desired peracetylated chacotriose 16 in
24% yield (Scheme 1).
3. Experimental
General methods.—Melting points were de-
termined on an electrothermal automatic ap-
paratus, and are uncorrected. Optical
rotations for solutions in CHCl3 or MeOH
h-
D
-glucofuranose (4).—To a stirred solution
-glu-
of 3-O-benzyl-1,2-O-isopropylidene-a-
D
cofuranose (3)13 (37 g, 119 mmol) in 1:1 tolu-
ene–pyridine (370 mL) was added, at
−10 °C, tosyl chloride (27.3 g, 143 mmol) in
toluene (50 mL). After 72 h at 6 °C, the
mixture was filtered and the filtrate concen-
trated under reduced pressure. The residue
was purified by column chromatography elut-
ing with 4:1 hexane–acetone to give 4 in 90%
1
yield as an oil; [h]D+73.2° (c 1.0, CHCl3); H
NMR (CDCl3, 300 MHz): l 7.90–7.11 (m, 9
H, Ph, C6H4), 5.60 (d, 1 H, J1,2 3.3 Hz, H-1),
4.58 (d, 1 H, J2,30.0 Hz, H-2), 4.50 (d, 1 H, J3,4
3.2 Hz, H-3), 4.30 (dd, 1 H, J6a,6b 10.0 Hz,
H-6a), 4.20 (m, 1 H, J5,6a 1.8 Hz, H-5), 4.10
(dd, 1 H, J5,6b 2.5 Hz, H-6b), 4.00 (m, 1 H, J4,5
4.0 Hz, H-4), 2.37 (s, 3 H, CH3C6H4), 1.20,
13
Scheme 1.
1.30 (2s, 6 H, CMe2); C NMR (CDCl3, 75.5

284
M. Morillo et al. / Carbohydrate Research 334 (2001) 281–287
ing with 4:1 hexane–acetone to give 6 isolated
in 76% yield as an oil; [h]D −87.9° (c 1.0,
CHCl3); 1H NMR (CDCl3, 300 MHz): l
7.30–7.20 (m, 10 H, Ph, C6H4), 5.85 (d, 1 H,
J1,2 3.5 Hz, H-1), 5.35 (m, 1 H, J5,6a 8.8 Hz,
H-5), 4.61–4.40 (4d, 4 H, CH2Ph), 4.51 (d, 1
H, J2,30.0 Hz, H-2), 4.40 (dd, 1 H, J4,5 6.0 Hz,
H-4), 3.90 (d, 1 H, J3,4 2.9 Hz, H-3), 3.75 (dd,
1 H, J6a,6b 11.1 Hz, H-6a), 3.65 (dd, 1 H, J5,6b
9.4 Hz, H-6b), 1.91 (s, 3 H, CH3CO), 1.27,
MHz): l 144.9 (Cipso), 137.0–127.8 (CH2Ph),
132.4–129.8 (C6H4), 111.8 (CMe2), 105.0 (C-
1), 81.9 (C-2), 81.8 (C-3), 81.6 (C-4), 79.1
(CH2Ph), 72.2 (C-5), 67.1 (C-6), 26.7, 26.1
(CMe2). Anal. Calcd for C23H28O8S: C, 59.47;
H, 6.08; S, 6.90. Found: C, 59.29; H, 5.98; S,
7.05.
5,6-Anhydro-3-O-benzyl-1,2-O-isopropyli-
dene-h- -glucofuranose (5).—To a stirred so-
D
lution of 4 (58 g, 125 mmol) in 9:1
1,4-dioxane–water (580 mL) was added pow-
dered NaOH (11 g, 275 mmol). After 2 h at rt,
the mixture was neutralized with satd aq
NH4Cl and extracted with toluene. The or-
ganic phase was separated, washed with water
(twice), dried (Na2SO4) and concentrated un-
der reduced pressure. The residue was purified
by column chromatography eluting with 9:1
hexane–acetone to give 5 in 76% yield as an
13
1.49 (2s, 6 H, CMe2). C NMR (CDCl3, 75.5
MHz): l 169.6 (CO), 138.2–127.4 (CH2Ph),
111.8 (CMe2), 105.1 (C-1), 81.6 (C-2), 80.8
(C-3), 77.6 (C-4), 71.9, 73.0 (CH2ꢀPh), 69.6
(C-6), 69.0 (C-5), 26.7, 26.3 (CMe2), 21.0
(CH3CO). Anal. Calcd for C25H30O7: C, 67.86;
H, 6.83. Found: C, 67.69; H, 6.98.
3,6-Di-O-benzyl-1,2-O-isopropylidene-h- -
D
glucofuranose (7).—To a stirred solution of 6
(29.8 g, 74 mmol) in MeOH (239 mL) was
added NaOMe (290 mg, 6 mmol). After 24 h
at rt, the mixture was neutralized with satd aq
NH4Cl and extracted with CH2Cl2. The or-
ganic phase was separated, washed with water
(twice), dried (Na2SO4) and concentrated un-
der reduced pressure to give 7 without further
oil; [h]D −9.7° (c 1.3, CHCl3); lit.21[h]D
−
1
8.6° (c 1.1, CHCl3); H NMR (CDCl3, 300
MHz): l 7.33–7.23 (m, 5 H, Ph, C6H4), 5.92
(d, 1 H, d, J1,2 3.7 Hz, H-1), 4.63 (2d, 2 H,
CH2Ph), 4.61 (d, 1 H, J2,30.0 Hz, H-2), 4.05
(d, 1 H, J3,4 3.2 Hz, H-3), 3.73 (dd, 1 H, J4,5
7.1 Hz, H-4), 3.28 (m, 1 H, J5,6a 3.9 Hz, H-5),
2.89 (dd, 1 H, J6a,6b 5.1 Hz, H-6a), 2.75 (dd, 1
H, J5,6b 2.5 Hz, H-6b), 1.28, 1.43 (2s, 6 H,
CMe2). 13C NMR (CDCl3, 75.5 MHz): l
127.5–137.3 (Ph), 111.8 (CMe2), 105.2 (C-1),
82.6 (C-2), 82.0 (C-3), 81.6 (C-4), 72.3
(CH2Ph), 48.1 (C-5), 46.9 (C-6), 26.8, 26.2
(CMe2). Anal. Calcd for C16H20O5: C, 65.74;
H, 6.89. Found: C, 65.89; H, 7.01.
purification in 99% yield as an oil; [h]D
−
1
24.9° (c 1.7, CHCl3); H NMR (CDCl3, 300
MHz): l 7.35–7.23 (m, 10 H, Ph), 5.90 (d, 1
H, J1,2 3.7 Hz, H-1), 4.67–4.49 (4d, 4 H,
CH2Ph), 4.57 (d, 1 H, J2,30.0 Hz, H-2), 4.09
(d, 1 H, J3,4 2.6 Hz, H-3), 4.17–4.08 (m, 2 H,
H-4, H-5), 3.72 (dd, 1 H, J5,6a 2.5, J6a,6b 9.7
Hz, H-6a), 3.58 (dd, 1 H, J5,6b 5.5 Hz, H-6b),
2.72 (d, 1 H, J5,OH 5.3 Hz, OH-5), 1.47, 1.29
(2s, 6 H, C-Me2); 13C NMR (CDCl3, 75.5
MHz): l 138.0–127.8 (Ph), 111.7 (CMe2),
105.1 (C-1), 82.3 (C-2), 82.0 (C-3), 79.8 (C-4),
73.4 (C-6), 72.3, 72.1 (CH2Ph), 68.0 (C-5),
26.8, 26.3 (CMe2). Anal. Calcd for C23H28O6:
C, 68.98; H, 7.05. Found: C, 69.11; H, 6.97.
5-O-Acetyl-3,6-di-O-benzyl-1,2-O-isopropy-
lidene-h- -glucofuranose (6).—To a stirred
D
solution of 5 (26 g, 89 mmol) and benzyl
alcohol (48 g, 445 mmol) in 1:1 toluene–
Me2SO (260 mL) was added powdered KOH
(30 g, 534 mmol). After 48 h at rt, the mixture
was filtered and the filtrate neutralized with
satd aq NH4Cl. The organic phase was sepa-
rated, washed with water (twice), dried
(Na2SO4) and concentrated under reduced
pressure. A solution of the residue (59.3 g) in
pyridine (593 mL) was treated with Ac2O
(41.7 mL) for 24 h at rt. Dichloromethane was
added and the mixture was then washed with
water (twice), dried (Na2SO4) and concen-
trated under reduced pressure. The residue
was purified by column chromatography elut-
3,6-Di-O-benzyl-
monoacetal derivative 7 (27 g, 67 mmol) was
added to stirred solution of 9:1
D
-glucopyranose (8).—The
a
CF3CO2OH–water (54 mL). After 30 min, at
rt, the solution was concentrated under re-
duced pressure. The residue was purified by
column chromatography eluting with 3:2 hex-
ane–EtOAc to give 8 in 86% yield as an oil,
a/b 3:2; [h]D +31.6° (c 1.8, MeOH); 13C
NMR (CDCl3, 75.5 MHz): l 8a 139.0, 138.0

M. Morillo et al. / Carbohydrate Research 334 (2001) 281–287
285
was neutralized with AcOH and concentrated
under reduced pressure. The residue was
purified by column chromatography eluting
with 17:3 hexane–acetone to give 11 in 98%
yield as an oil; [h]D −51.9° (c 0.1, CHCl3); 1H
NMR (CDCl3, 300 MHz): l 7.21–7.12 (m, 10
H, Ph), 4.78–4.45 (CH2Ph), 4.20 (d, 1 H, J1,2
7.7 Hz, H-1), 3.59 (m, 2 H, J6a,6b 10.5 Hz,
H-6), 3.45 (t, 1 H, J4,5 9.4 Hz, H-4), 3.45 (dd,
1 H, J2,3 9.1 Hz, H-2), 3.30 (m, 1 H, J5,6a and
J5,6b 5.2 Hz, H-5), 3.23 (t, 1 H, J3,4 8.9 Hz,
(Cipso), 129.4–128.4 (Ph), 92.8 (C-1), 82.5 (C-
3), 75.2, 74.2 (CH2Ph), 72.8 (C-2), 71.2 (C-4),
70.5 (C-5), 70.4 (C-6); 8b 139.0, 138.0 (Cipso),
129.4–128.4 (Ph), 97.1 (C-1), 84.3 (C-3), 75.2,
74.2 (CH2Ph), 74.0 (C-2), 71.2 (C-4), 70.5
(C-5), 70.4 (C-6). Anal. Calcd for C20H24O6:
C, 66.65; H, 6.71. Found: C, 66.41; H, 6.52.
1,2,4-Tri-O-acetyl-3,6-di-O-benzyl- -gluco-
D
pyranose (9).—To a stirred solution of 8 (20.8
g, 57 mmol) in pyridine (276 mL) was added
Ac2O (27 mL, 288 mmol). After 24 h at rt, the
mixture was diluted with CH2Cl2 and washed
with water (twice), dried (Na2SO4) and con-
centrated under reduced pressure. Compound
9 was isolated without further purification in
86% yield as an oil, a/b 13:1; [h]D +28° (c
13
H-3); C NMR (CDCl3, 75.5 MHz): l 138.3–
128.2 (Ph), 102.1 (C-1), 84.2 (C-3), 75.1, 74.1,
71.0 (CH2Ph), 74.9 (C-2), 74.7 (C-4), 71.6
(C-5), 70.6 (C-6). Anal. Calcd for C27H30O6:
C, 71.98; H, 6.71. Found: C, 72.15; H, 6.82.
13
1.1, CHCl3); C NMR (CDCl3, 75.5 MHz): l
Benzyl 2,3,4-tri-O-acetyl-h-
osyl-(1“4)-3,6-di-O-benzyl-i-
oside (14) and benzyl 2,3,4-tri-O-acetyl-h-
rhamnopyranosyl-(1“2)-[(2,3,4-tri-O-acetyl-
h- -rhamnopyranosyl-(1“4)]-3,6-di-O-ben-
zyl-i- -glucopyranoside (15).—To a stirred
L
-rhamnopyran-
169.5, 169.2, 168.8 CH3CO), 137.9–127.4
(Ph), 92.0 (C-1b), 89.4 (C-1a), 79.9 (C-3b) 77.4
(C-3a) 76.9 (C-2b) 76.5 (C-2a) 74.5, 73.5
(CH2Ph) 71.5 (C-5) 70.7 (C-4) 69.6 (C-6).
Anal. Calcd for C26H30O9: C, 64.19; H, 6.21.
Found: C, 64.38; H, 6.14.
D
-glucopyran-
L
-
L
D
solution of bromide derivative 13 (8.6 g, 24
mmol) and benzyl derivative 11 (2.5 g, 6
mmol) in anhyd CH2Cl2 (66 mL) was added,
at 0 °C in the dark, tetramethylurea (2.65 mL,
24 mmol) and CF3SO3Ag (4.28 g, 84 mmol).
After 48 h at rt in the dark, the mixture was
filtered and extracted with CH2Cl2–water. The
organic phase was separated, washed with wa-
ter (twice), dried (Na2SO4) and concentrated
under reduced pressure. Column chromatog-
raphy eluting with hexane–acetone allowed to
obtain first 14 in 30% yield as an oil; [h]D
Benzyl 2,4-di-O-acetyl-3,6-di-O-benzyl-i-
-glucopyranoside (10).—To a stirred solution
D
of 9 (24 g, 49 mmol) and benzyl alcohol (5.6 g,
54 mmol) in CH2Cl2 (240 mL) was added
SnCl4 (6.35 mL, 54 mmol). After 24 h at rt,
the mixture was filtered and the filtrate neu-
tralized with solid NaHCO3. The solution was
concentrated under reduced pressure. The
residue was purified by column chromatogra-
phy eluting with 22:3 hexane–acetone to give
10 in 60% yield as white crystals; mp 73–
1
13
74 °C, [h]D −30.9° (c 1.2, CHCl3); H NMR
−12° (c 1.2, CHCl3); C NMR (CDCl3, 75.5
(CDCl3, 300 MHz): l 7.39–7.26 (m, 10 H,
Ph), 5.15 (dd, 1 H, J2,3 9.4 Hz, H-2), 5.14 (t, 1
H, J4,5 9.5 Hz, H-4), 4.93–4.60 (CH2Ph), 4.49
(d, 1 H, J1,2 7.9 Hz, H-1), 3.70 (t, 1 H, J3,4 9.4
Hz, H-3), 3.61 (m, 3 H, H-5, H-6), 2.03 1.92
(2s, 6 H, CH3CO); 13C NMR (CDCl3, 75.5
MHz): l 170.0–169.7 (CH3CO), 138.3–128.2
(Ph), 99.9 (C-1), 80.6 (C-3), 73.9 (C-2), 73.0
(C-4), 71.2 (C-5), 70.1 (C-6), 74.1, 70.8
(CH2Ph), 21.3 (CH3CO). Anal. Calcd for
C31H34O8: C, 69.65; H, 6.41. Found: C, 69.41;
H, 6.17.
MHz): l glucose 137.9–127.2 (Ph), 98.6 (C-1),
81.8 (C-3), 75.6, 74.0, 71.4 (CH2Ph), 74.6 (C-
4), 73.5 (C-2), 70.9 (C-5), 68.6 (C-6), rhamnose
(1“4) 170.7–170.3 (CH3CO), 97.4 (C-1), 70.6
(C-4), 70.5 (C-2), 69.5( C-3), 67.1 (C-5), 21.2
(CH3CO), 17.3 (C-6). Anal. Calcd for
C39H46O13: C, 64.81; H, 6.41. Found: C, 65.09;
H, 6.37. Mass spectrometry: FAB-MS;
[M+Li]+ m/z 729, C12H17O+7 m/z 273.
Benzyl 2,3,4-tri-O-acetyl-a-
L
-rhamnopyran-
-rhamno-
-gluco-
osyl-(1“2)-[2,3,4-tri-O-acetyl-a-
L
pyranosyl-(1“4)]-3,6-di-O-benzyl-b-
D
Benzyl 3,6-di-O-benzyl-i-
D
-glucopyranoside
pyranoside (15) was obtained next in 65%
13
(11).—To a stirred solution of 10 (5.7 g, 105
mmol) in MeOH (45 mL) was added NaOMe
(45 mg, 6 mmol). After 3 h at rt, the mixture
yield as an oil; [h]D −69° (c 0.8, CHCl3); C
NMR (CDCl3, 75.5 MHz): l glucose 137.4–
127.7 (Ph), 100.3 (C-1), 81.0 (C-3), 79.6 (C-2),

286
M. Morillo et al. / Carbohydrate Research 334 (2001) 281–287
2.14 (s, 6 H, 2 CH3CO), 2.12 (s, 3 H, CH3CO),
2.05 (s, 6 H, 2 CH3CO), 2.01, 1.99 (2 s, 6 H,
2 CH3CO); 13C NMR (CDCl3, 75.5 MHz): l
glucose 89.9 (C-1), 77.2 (C-4), 76.6 (C-2), 71.8
(C-3), 70.3 (C-5), 61.7 (C-6), rhamnose (1“4)
99.5 (C-1), 70.6 (C-4), 70.2 (C-2), 68.4 (C-3),
67.8 (C-5), 17.2 (C-6), rhamnose (1“2) 99.1
(C-1), 70.6 (C-4), 70.0 (C-2), 68.2 (C-3), 67.3
(C-5), 17.2 (C-6). 170.5–168.5 (CH3CO),
75.8, 73.5, 69.7 (CH2Ph), 75.4 (C-4), 70.9 (C-
5), 68.5 (C-6), rhamnose(1“4) 170.6–169.9
(CH3CO), 97.2(C-1), 71.2 (C-4), 70.5 (C-2),
69.3(C-3), 67.2 (C-5), 21.2 (CH3CO), 17.3 (C-
6), rhamnose(1“2) 170.6–169.9 (CH3CO),
97.7(C-1), 71.2 (C-4), 70.0 (C-2), 69.3( C-3),
67.2 (C-5), 21.2 (CH3CO), 17.3 (C-6). Anal.
Calcd for C51H62O20: C, 61.56; H, 6.28.
Found: C, 61.28; H, 6.03. Mass spectrometry:
FAB-MS; [M+Li]+ m/z 1001, C12H17O+7 m/z
273.
1
21.1–20.4 (CH3CO). 16b anomer. H NMR
(CDCl3, 300 MHz): l Glucose 5.68 (d, 1 H,
J1,2 8.1 Hz, H-1), 5.33 (t, 1 H, J3,4 8.8 Hz,
H-3), 4.43 (dd, 1 H, J5,6a 1.4, J6a,6b 12.6 Hz,
H-6a), 4.33 (dd, 1 H, J5,6b 3.4 Hz, H-6b), 3.81
(t, 1 H, J4,5 10.8 Hz, H-4), 3.78 (ddd, 1 H,
H-5), 3.64 (dd, 1 H, J2,3 9.3 Hz, H-2), rham-
nose (1“4) 5.19 (dd, 1 H, J3,4 10.2 Hz, H-3),
5.05 (t, 1 H, J4,5 9.7 Hz, H-4), 5.01 (dd, 1 H,
J2,3 3.2 Hz, H-2), 4.83 (d, 1 H, J1,2 2.1 Hz,
H-1), 3.86 (dq, 1 H, J5,6 6.2 Hz, H-5), 1.17 (d,
3 H, H-6), rhamnose (1“2) 5.11 (dd, 1 H, J3,4
10.2 Hz, H-3), 5.07 (dd, J2,3 3.4 Hz, 1 H, H-2),
5.04 (t, 1 H, J4,5 9.3 Hz, H-4), 4.85 (d, 1 H, J1,2
1.8 Hz, H-1), 3.91 (dq, 1 H, J5,6 6.3 Hz, H-5),
1.16 (d, 3 H, H-6). 2.20, 2.15 (2 s, 6 H, 2
CH3CO), 2.14 (s, 6 H, 2 CH3CO), 2.12, 2.05,
2.04, 2.00, 1.97 (5s, 15 H, 5 CH3CO); 13C
NMR (CDCl3, 75.5 MHz): l glucose 92.5
(C-1), 78.7 (C-2), 77.0 (C-4), 74.0 (C-3), 73.1
(C-5), 61.7 (C-6), rhamnose (1“4) 99.5 (C-1),
70.5 (C-4), 70.1 (C-2), 68.4 (C-3), 67.9 (C-5),
17.1 (C-6), rhamnose (1“2) 98.6 (C-1), 70.5
(C-4), 69.8 (C-2), 68.7 (C-3), 67.2 (C-5), 17.2
(C-6), 170.5–168.5 (CH3CO), 21.1–20.4
(CH3CO).
2,3,4-Tri-O-acetyl-h-
(1“2)-[2,3,4-tri-O-acetyl-h-
osyl - (1“4)] - 1,3,6 - tri - O - acetyl -
L
-rhamnopyranosyl-
-rhamnopyran-
- gluco-
L
D
pyranose (16).—A mixture of prehydro-
genated 5% Pd–C catalyst (263 mg) in EtOH
and 15 (606 mg, 0.61 mmol) dissolved in
EtOH (20 mL) was shaken in a hydrogen
atmosphere (1 atm) during 96 h. The catalyst
was filtered off and EtOH evaporated under
vacuum to give an oil. The mixture was dis-
solved in pyridine (1 mL) and was added
Ac2O (1 mL). After 12 h at rt, iced water was
added and the product extracted with EtOAc.
The organic layer was washed several times
with water, dried (Na2SO4) and evaporated
under reduced pressure several times with tol-
uene. The residue was purified by column
chromatography eluting with 13:7 hexane–
EtOAc to give 16 in 24% yield as an oil, a/b
2:1; [h]D 1.5° (c 1.1, CHCl3). Anal. Calcd for
C36H50O23: C, 50.82; H, 5.92. Found: C, 51.09;
H, 5.94. Mass spectrometry: EI-MS; [M−
CH3CO2H]+ m/z 790, C12H16O+7 m/z 272,
’
’
[C12H16O7−2CH3CO2H]+ m/z 152. ESI-MS;
’
[M+NH4]+ m/z 868, C12H17O+7 m/z 273. 16a
anomer. H NMR (CDCl3, 300 MHz): l Glu-
1
cose 6.27 (d, 1 H, J1,2 3.7 Hz, H-1), 5.51 (t, 1
H, J3,4 9.3 Hz, H-3), 4.38 (dd, 1 H, J5,6a 1.9,
J6a,6b 12.5 Hz, H-6a), 4.34 (dd, 1 H, J5,6b 3.3
Hz, H-6b), 4.03 (ddd, 1 H, H-5), 3.79 (t, 1 H,
J4,5 9.9 Hz, H-4), 3.76 (dd, 1 H, J2,3 10.0 Hz,
H-2), rhamnose (1“4) 5.23 (dd, 1 H, J2,3 3.2,
J3,4 10.1 Hz, H-3), 5.06 (t, 1 H, H-4), 5.02 (dd,
1 H, J1,2 1.7 Hz, H-2), 4.83 (d, 1 H, H-1), 3.88
(dq, 1 H, J4,5 9.6, J5,6 6.2 Hz, H-5), 1.18 (d, 3
H, H-6), rhamnose (1“2) 5.16 (dd, 1 H, J2,3
3.4, J3,4 10.1 Hz, H-3), 5.04 (t, 1 H, H-4), 5.02
(dd, 1 H, H-2), 4.82 (d, 1 H, J1,2 1.6 Hz, H-1),
3.80 (dq, 1 H, J4,5 9.5, J5,6 6.2 Hz, H-5), 1.18
(d, 3 H, H-6). 2.27, 2.17 (2 s, 6 H, 2 CH3CO),
Acknowledgements
Thanks are given to the Postgraduate Co-
operation Program ‘PCP Surfactants and Ap-
plications’ which is sponsored by CEFI
(France) and CONICIT (Venezuela), G.
Mackenzie for helpful discussions and S. Pi-
lard for mass spectrometry.
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