Highly efficient syntheses of the phytoalexin-elicitor active β- (1→3)-branched β-(1→6)-linked heptaglucose and its dodecyl glycoside

Article abstract of DOI:10.1055/s-2003-37644

A highly efficient method for the synthesis of 3,6-branched gluco-oligosaccharides was developed by using 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose, 2,3,4,6-tetra-O-benzoyl-α-D-glucopyranosyl trichloroacetimidate, and 6-O-acetyl-2,3,4-tri-O-benzoyl-α-

Full text of DOI:10.1055/s-2003-37644

PAPER
491
Highly Efficient Syntheses of the Phytoalexin-Elicitor Active β-(1→3)-
Branched β-(1→6)-Linked Heptaglucose and Its Dodecyl Glycoside
Efficient
S
ynthese
u
s
of
O
ligosac
e
charides tao Yi,a Zhongxuan Zhou,a Jun Ning,*a Fanzuo Kong,a Jianqiang Lib
a
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P. O. Box 2871, Beijing 100085, China
b
Department of Plant Pathology, China Agricultural University, Beijing 100094, China
Fax +86(10)62923563; E-mail: jning@mail.rcees.ac.cn
Received 31 October 2002; revised 17 December 2002
most active heptasaccharide 1 (Figure1) is effective in
very low doses, approximately 0.1 pmol per cotyledon.3 It
should be noted that, although much of this work was
done with soybean cotyledons, it was established that the
Abstract: A highly efficient method for the synthesis of 3,6-
branched gluco-oligosaccharides was developed by using 1,2:5,6-
di-O-isopropylidene- -D-glucofuranose, 2,3,4,6-tetra-O-benzoyl-
-D-glucopyranosyl trichloroacetimidate, and 6-O-acetyl-2,3,4-tri-
O-benzoyl- -D-glucopyranosyl trichloroacetimidate through a re- glucan-elicitor also elicited the synthesis of different phy-
toalexins in a wide range of other plant species.4 These
important discoveries stimulated the interest of scientists.
gio- and stereoselective manner. The -(1→3)-branched -(1→6)-
linked heptaglucose 1 and its dodecyl glycoside 2 having phytoal-
exin-elicitor activity were prepared using the developed strategy.
Since their isolation and identification, the glucan-elici-
Bioassays showed that the phytoalexin-elicitor activity of the do-
decyl -(1→3)-branched -(1→6)-linked hexaglucoside 2 is slight-
tors have been prepared by different groups,5 and various
methods and strategies have been used including the very
elegant solid-phase strategies.5k,l Recently, in a prelimi-
nary communication, we have disclosed a newly efficient
method suitable for large scale synthesis of 3,6-branched
β-linked gluco-oligosaccharids using 1,2:5,6-di-O-iso-
propylidene-α-D-glucofuranose as the starting material,
and the β-(1→3)-branched β-(1→6)-linked glucohexaose
phytoalexin-elicitor on a 100 g scale was achieved in our
laboratory.6
ly more than that of the corresponding reducing end free
heptaglucose 1.
Key words: oligosaccharides, phytoalexin-elicitor, synthesis, gly-
cosides, glycosylations
A central problem in carbohydrate chemistry is how to
prepare oligosaccharides efficiently and simply. In the last
decades, much effort has been paid to the oligosaccharide
synthesis. However, up to date, there are no general appli-
cable methods or strategies for oligosaccharide synthesis,
and consequently the preparation of oligosaccharides is
very time consuming compared with the synthesis of other
biopolymers such as peptides and nucleic acids. Generally
speaking, production of a complex oligosaccharide on an
industrial scale is very difficult if not impossible so far.
We always ask the question as to which method is the
most suitable in carbohydrate synthesis. Does a single
powerful method or strategy in the synthesis of oligosac-
charides really exist? Maybe, owing to this structural
Figure 1 Glucose heptasaccharide 1 and its dodecyl glycoside 2
complexity, the preparation of oligosaccharides will never Some research reports show that modification of oligosac-
achieve the same levels as the preparation of peptides and charides with hydrophobic long alkyls at the reducing ter-
nucleic acids, but we can create relatively general proce- minal can increase their biological activity.7 The reason is
dures which are peculiarly effective for certain types of that the newly formed compounds are composed both of a
oligosaccharides.
hydrophilic oligosaccharide portion and a hydrophobic
long alkyl portion, and have the characteristic of a sur-
face-active agent able to coagulate together. In search of
higher phytoaleaxin-elicitor active oligosaccharides, a
dodecyl β-(1→3)-branched β-(1→6)-linked heptagluco-
side 2 was synthesized in our laboratory. In this paper, we
present in detail the syntheses of the heptaglucose 1 and
its dodecyl glycoside 2. Also the bioassay results of the
compounds 1 and 2 as the phytoaleaxin-elicitors are giv-
en.
3,6-Branched gluco-oligosaccharides are a common
structure characteristic of many biologically active
polysaccharides such as the phytoalexin-elicitor β-glucan
and antitumor polysaccharides from schizophyllan, scero-
glucan, and lentinan.1 The β- (1→3)-branched β-(1→6)-
linked glucose oligomers isolated from mycelial walls of
the fungus Phytophthora megasperma f. sp. Glycinea can
induce the formation of phytoalexins in soybean.2 The
In our synthesis, 1,2:5,6-di-O-isopropylidene-α-D-gluco-
furanose (4), 3-O-benzoyl-1,2-O-isopropylidene-α-D-
glucofuranose (5), 2,3,4,6-tetra-O-benzoyl-α-D-glucopy-
Synthesis 2003, No. 4, Print: 18 03 2003.
Art Id.1437-210X,E;2003,0,04,0491,0496,ftx,en;F08702SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

492
Y. Yi et al.
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ranosyl trichloroacetimidate (6), 6-O-acetyl-2,3,4-tri-O- quent treatment with trichloroacetonitrile in the presence
benzoyl-α-D-glucopyranosyl trichloroacetimidate (8) and of K2CO3 afforded the desired trisaccharide glycosyl do-
dodecyl 2,3,4-tri-O-benzoyl-β-D-glucopyranoside (10) nor 13 in 71% yield (for four steps). Condensation of 11
were the basic building materials. Compound 4 was ob- with 8 afforded the 3,6-branched trisaccharide 14 in 85%
tained according to the standard method.8 Compound 5 yield. Selective 6-O-deacetylation of 14 in CH2Cl2–
was prepared from 4.9 Compound 6 was obtained as fine MeOH containing 0.3% HCl gave the trisaccharide accep-
crystals from benzoylation of D-glucose, followed by 1- tor 15 in 90% yield.
O-debenzoylation with ammonium in THF–MeOH and
trichloroacetimidation (Scheme 1). Compound 8 was pre-
pared as crystals by the benzoylation of 1,6-anhydro-β-D-
glucopyranose (7, levoglucosan), a cheap material ob-
tained from the pyrolysis of cellulose,10 followed by ace-
tolysis, 1-O-deacetylation, and trichloroacetimidation.
Coupling of 8 with dodecyl alcohol gave compound 9
which was selectively converted to 10 using MeOH con-
taining 0.3% HCl. The solution of MeOH containing HCl
was formed in situ by adding acetyl chloride to MeOH.
Scheme 2 Preparation of the trisaccharide donor 13 and acceptor 15
Coupling of 13 with 15 with TMSOTf as the catalyst af-
forded regio- and stereoselectively the blocked hexasac-
charide 16 in a high yield (84%) (Scheme 3). Using the
same operations for the preparation of the trisaccharide
glycosyl donor 13, the hexasaccharide glycosyl donor 18
was obtained from 17.
Coupling of 17 with 5 and 10 afforded the blocked hep-
tasaccharides 18 and 19, respectively (Scheme 4). Deiso-
propylidenation of 18 in 80% HOAc, followed by
deacetylation in an ammonia-saturated solution of 1:9
CH2Cl2–MeOH, furnished the free heptasaccharide 1 as
an amorphous white solid in 90% yield. Deprotection of
19 gave 2.
Scheme 1 Preparation of building materials 4, 5, 6, 8, and 10
Coupling of 1,2:5,6-di-O-isopropylidene-α-D-glucofura-
nose (4) with perbenzoylglucosyl trichloroacetimidate 6
in the presence of TMSOTf as catalyst, followed by selec-
tive 5,6-O-deacetonation afforded β-(1→3)-linked disac-
charide 11 as crystals in a high yield (76% for two steps)
(Scheme 2). Condensation of 11 with 6 catalyzed by TM-
SOTf gave regio- and stereoselectively the 3,6-branched
trisaccharide 12 in 87% yield. Removal of the 1,2-O-iso-
propylidene group of 12 in 80% HOAc followed by acety-
lation with acetic anhydride in pyridine, selective 1-O-
deacetylation with ammonia in THF–MeOH, and subse-
In all of the synthesis, very easily accessible materials and
cheap reagents were used and the reactions were carried
out smoothly in high yields and in large scales. In the syn-
thesis, several intermediates were not separated and used
directly for the further reaction simplifying the operation
substantially. The sole use of acyl groups in the synthesis
further simplified the procedure.
The bioassay was carried out according to the method de-
vised by Ayers et al.11 The phytoalexin-elicitor sugars can
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Efficient Syntheses of Oligosaccharides
493
Optical rotations were determined at 20 °C with a Perkin-Elmer
Model 241-Mc automatic polarimeter. Melting points were deter-
mined with a Mel-Temp apparatus. 1H NMR and 13C NMR spectra
were recorded with Bruker ARX 400 spectrometers (400 MHz for
1H, 100 MHz for 13C) for solutions in CDCl3 or D2O as indicated.
Chemical shifts are given in ppm downfield from internal Me4Si.
TLC was performed on silica gel HF254 with detection by charring
with 30% (v/v) H2SO4 in MeOH or in some cases by a UV detector.
Column chromatography was conducted by elution of a column
(3 × 30 cm, 6.5 × 50 cm, 9 × 60 cm, 12 × 80 cm) of silica gel (100–
200 mesh) with EtOAc–petroleum ether (bp 60–90 °C) as eluent.
Solutions were concentrated at <60 °C under reduced pressure.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl Trichloroacetimi-
date (6)
BzCl (680 mL, 5.83 mol) was added under vigorous stirring to a so-
lution of D-glucose (3; 200 g, 1.11 mol) in toluene (2500 mL) and
pyridine (473 mL, 5.85 mol) over 1 h at 70 °C, and then the mixture
was stirred at 70 °C for further 7 h. Filtration of pyridine hydro-
chloride salt and concentration of the filtrate gave a residue which
was directly dissolved in a solution of NH3 (1.5 N) in 2:1 THF–
MeOH (5600 mL). The solution was kept at r.t. for 12 h, at the end
of which time TLC (petroleum ether–EtOAc, 3:1) indicated that the
reaction was complete. The mixture was concentrated under re-
duced pressure, and the residue was dissolved in CH2Cl2 (1000 mL),
and then CCl3CN (120 mL, 1.2 mol) and K2CO3 (300 g, 2.17 mol)
were added. The reaction mixture was stirred for 24 h at r.t., at the
end of which time TLC (petroleum ether–EtOAc, 3:1) indicated that
the reaction was complete. The mixture was filtered, the solution
was concentrated under reduced pressure, and the residue was de-
colorized by passing through a short column (12 × 80 cm) packed
with silica gel (2500 mL) using petroleum ether–EtOAc (3:1) as
eluent. The product 6 was further purified by crystallization from
petroleum ether–EtOAc, 3:1; white crystals; yield: 461 g (56% for
three steps).12
Scheme 3 Preparation of the hexasaccharide donor 17
stimulate glyceollin accumulation in cotyledons of soy-
bean seedlings. The activities of the synthesized oligosac-
charides were determined by their
concentrations
required to elicit half-maximal accumulation of glyceollin
(C50). The test results showed that C50 of the dodecyl β-
(1→3)-branched β-(1→6)-linked hexaglucoside 2 and its
underivatized 1 are about 6 nM and 9 nM respectively, in-
dicating that modification of the reducing-end of this oli-
gosaccharide does not have a significant effect on its
biological activity. Similar conclusion was reported by
others.5h
6-O-Acetyl-2,3,4-tri-O-benzyol- -D-glucopyranosyl Trichloro-
acetimidate (8)
BzCl (223 mL, 1.92 mol) was added under vigorous stirring to a so-
lution of 7 (100 g, 0.62 mmol) in toluene (700 mL) and pyridine
(158 mL, 1.95 mmol) over 1 h. The mixture was warmed to 70 °C,
and then stirred at 70 °C for 7 h. Filtration of pyridine hydrochloride
salt and concentration of the filtrate gave a residue which was di-
rectly dissolved in a mixture of CH2Cl2 (230 mL), Ac2O (230 mL,
2.44 mol), and AcOH (230 mL). Then H2SO4 (23 mL) was added
dropwise. This reaction mixture was kept for 20 h at r.t., then poured
into ice water. After stirring for 15 min, the mixture was extracted
with CH2Cl2. The combined CH2Cl2 extracts were washed with
10% aq NaHCO3, and then concentrated to a syrup. The resulting
residue was added to a solution of NH3 (1.5 N) in THF–MeOH, 2:1
(2400 mL). The solution was kept at room temperature for 3 h, at
the end of which time TLC (petroleum ether–EtOAc, 3:1) indicated
that the reaction was complete. The mixture was concentrated under
reduced pressure, and the residue was dissolved in CH2Cl2 (500
mL), and then CCl3CN (86 mL, 0.85 mol) and K2CO3 (200 g, 1.45
mol) were added. The reaction mixture was stirred for 24 h at r.t., at
the end of which time TLC (petroleum ether–EtOAc, 3:1) indicated
that the reaction was complete. The mixture was filtered, the solu-
tion was concentrated under reduced pressure, and the residue was
purified on a column (9 × 60 cm) packed with silica gel (3000 mL)
using petroleum ether–EtOAc (3:1) as eluent to give 8 as white
crystals; yield: 226.3 g (54% for four steps); mp 81–83 °C; [ ]D
+9.0 (c = 1.3, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 8.65 [s, 1 H, OC(NH)CCl3], 7.96–
7.26 (m, 15 H, 3 PhH), 6.82 (d, 1 H, J1,2 = 3.6 Hz, H-1), 6.24 (dd, 1
H, J2,3 = J3,4 = 9.8 Hz, H-3), 5.74 (dd, 1 H, J3,4 = J4,5 = 9.8 Hz, H-4),
Scheme 4 Preparation of heptasaccharide 1 and its dodecyl glyco-
side 2
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5.59 (dd, 1 H, J1,2 = 3.6, J2,3 = 9.8 Hz, H-2), 4.50 (m, 1 H, H-5), 4.30
(m, 2 H, H-6,6′), 2.07 (s, 3 H, COCH3).
3,6-Di-O-(2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl)-1,2-O-
isopropylidene- -D-glucofuranose (12); Typical Procedure
To a stirred solution of 11 (80 g, 0.1 mol) and 6 (80 g, 0.108 mol)
in anhyd CH2Cl2 (400 mL) was added TMSOTf (200 µL, 1.0 mmol)
at r.t. After 3 h, Et3N was added to the solution to quench the reac-
tion. The solution was concentrated and the residue was subjected
to column chromatography on silica gel (9 × 60 cm, 3000 mL) using
petroleum ether–EtOAc (1.5:1) as eluent to give the trisaccharide
12 as a white amorphous solid; yield: 119.8 g (87%); [ ]D +25.3
(c = 1.0, CHCl3).
Anal. Calcd for C31H26Cl3NO10: C, 54.84; H, 3.86. Found: C, 54.72;
H, 3.90.
Dodecyl 6-O-Acetyl-2,3,4-tri-O-benzyol- -D-glucopyranoside
(9)
To a stirred solution of 8 (4 g, 5.89 mmol) and dodecyl alcohol (1.9
g, 10.2 mmol) in anhyd CH2Cl2 (80 mL) was added trimethylsilyl
trifluoromethanesulfonate (TMSOTf, 40 µL) at r.t. After 3 h, Et3N
was added to the solution to quench the reaction. The solution was
concentrated, the residue was subjected to column chromatography
on silica gel (3 × 30 cm, 150 mL) using petroleum ether–EtOAc
(3:1) as eluent to give the trisaccharide 9; 3.8 g (92%); [ ]D +34.2
(c = 1.0, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 7.98–7.24 (m, 15 H, 3 PhH), 5.91
(dd, 1 H, J2,3 = J3,4 = 9.7 Hz, H-3), 5.63 (dd, 1 H, J3,4 = J4,5 = 9.7 Hz,
H-4), 5.50 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.7 Hz, H-2), 4.82 (d, 1 H,
J1,2 = 7.9 Hz, H-1), 4.36 (dd, 1 H, J5,6 = 4.8, J6,6′ = 12.2 Hz, H-6),
4.29 (dd, 1 H, J5,6′ = 3.5, J6,6′ = 12.2 Hz, H-6′), 4.06 (m, 1 H, H-5),
3.95–3.55 (m, 2 H, CH2C11H23), 2.03 (s, 3 H, COCH3), 1.54–0.86
(m, 23 H, CH2C11H23).
1H NMR (400 MHz, CDCl3): δ = 8.06–7.28 (m, 40 H, 8 PhH), 5.88
(dd, 1 H, J2,3 = J3,4 = 9.7 Hz, H-3b), 5.87 (dd, 1 H, J2,3 = J3,4 = 9.7
Hz, H-3c), 5.69 (dd, 1 H, J3,4 = J4,5 = 9.7 Hz, H-4b), 5.64 (dd, 1 H,
J
3,4 = J4,5 = 9.7 Hz, H-4c), 5.53 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.7 Hz, H-
2b), 5.43 (dd, 1 H, J1,2 = 7.9 Hz, J2,3 = 9.7 Hz, H-2c), 5.41 (d, 1 H,
J
1,2 = 3.5 Hz, H-1a), 4.96 (d, 1 H, J1,2 = 7.9 Hz, H-1b), 4.93 (d, 1 H,
J1,2 = 7.9 Hz, H-1c), 4.68 (dd, 1 H, J5,6 = 3.4, J6,6′ = 12.2 Hz, H-6b),
4.48 (dd, 1 H, J5,6′ = 4.9, J6,6′ = 12.2 Hz, H-6b′), 4.67 (dd, 1 H,
J
5,6 = 3.4, J6,6′ = 12.2 Hz, H-6c), 4.35 (dd, 1 H, J5,6 = 4.9, J6,6 = 12.2
Hz, H-6c′), 4.34–3.65 (m, 8 H), 1.26, 1.03 [2 s, 6 H, C(CH3)2].
Anal. Calcd for C77H68O24: C, 67.15; H, 4.98. Found: C, 67.29; H,
5.02.
Anal. Calcd for C41H50O10: C, 70.07; H, 7.17. Found: C, 70.36; H,
7.28.
2,4-Di-O-acetyl-3,6-di-O-(2,3,4,6-tetra-O-benzoyl- -D-glucopy-
ranosyl)- -D-glucopyranosyl Trichloroacetimidate (13); Typi-
cal Procedure
Dodecyl 2,3,4-Tri-O-benzyol- -D-glucopyranoside (10)
Acetyl chloride (0.6 mL) was added to a solution of 9 (3 g, 4.27
mmol) in MeOH (100 mL), and the mixture was kept at r.t. for 20
h. After neutralization with Et3N and concentration, the residue was
subjected to column chromatography on silica gel (3 × 30 cm, 150
mL) using petroleum ether–EtOAc (2:1) as eluent to give 10; yield:
2.65 g (94%); [ ]D +38.6 (c = 1.0, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 7.88–7.15 (m, 15 H, 3 PhH), 5.86
(t, 1 H, J2,3 = J3,4 = 9.8 Hz, H-3), 5.45–5.40 (m, 2 H, H-2, 4), 4.75
(d, 1 H, J1,2 = 7.9 Hz, H-1), 3.87–3.44 (m, 5 H, H-5, 6, 6′,
CH2C11H23), 1.45–0.77 (m, 23 H, CH2C11H23).
Compound 12 (50 g, 0.036 mol) was added to 80% aq AcOH (500
mL) and the mixture was refluxed for 4 h. The mixture was concen-
trated and the residue was acetylated by stirring with Ac2O (250
mL) in pyridine (280 mL) for 2 h at r.t. The resultant trisaccharide
was added to a solution of ammonia (1.5 N) in THF–MeOH, 3:1
(500 mL) and the solution was stirred at r.t. for 3 h. The solution was
concentrated and the residue was dissolved in CH2Cl2 (200 mL). To
the solution were added K2CO3 (10 g, 0.072) and CCl3CN (8 mL,
0.072 mol), and the mixture was stirred at r.t. for 12 h. The mixture
was filtered and the solids were washed with CH2Cl2. The filtrate
and the washings were concentrated, and the residue was subjected
to column chromatography on silica gel (6.5 × 50 cm, 1300 mL) us-
ing petroleum ether–EtOAc (2:1) as eluent to give the trisaccharide
donor 13 as a white amorphous solid; yield: 40.4 g (71% for four
steps); [ ]D +23.3 (c = 1.0, CHCl3).
Anal. Calcd for C39H48O9: C, 70.89; H, 7.32. Found: C, 70.51; H,
7.39.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→3)-1,2-O-iso-
propylidene- -D-glucofuranose (11)
1H NMR (400 MHz, CDCl3): δ = 8.33 [s, 1 H, O(NH)CCl3], 8.07–
7.19 (m, 40 H, 8 PhH), 6.19 (d, 1 H, J1,2 = 3.6 Hz, H-1a), 5.91 (dd,
1 H, J2,3 = J 3,4 = 9.6 Hz, H-3b), 5.85 (dd, 1 H, J2,3 = J 3,4 = 9.6 Hz,
H-3c), 5.62 (dd, 1 H, J3,4 = J 4,5 = 9.6 Hz, H-4b), 5.61 (dd, 1 H,
To a stirred solution of 4 (100 g, 0.38 mol) and 6 (260 g, 0.35 mol)
in anhyd CH2Cl2 (3000 mL) was added TMSOTf (700 µL, 35
mmol) at r.t. After 3 h, Et3N was added to the solution to quench the
reaction. The solution was concentrated, and the residue was added
to a 90% aq AcOH (5000 mL). The mixture was kept at 40 °C for
20 h and then concentrated under reduced pressure. The residue was
subjected to column chromatography on silica gel (9 × 60 cm, 2500
mL) using petroleum ether–EtOAc, (1:1) as eluent to give 11 as
white crystals; yield: 213 g (76% for two steps); mp 121–123 °C;
[ ]D +34.0 (c = 2.5, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 8.11–7.28 (m, 20 H, 4 PhH), 5.94
(dd, 1 H, J2′,3′ = J3′,4′ = 9.7 Hz, H-3′), 5.72 (dd, 1 H, J3′,4′ = J4′,5′ = 9.7
Hz, H-4′), 5.54 (dd, 1 H, J1′,2′ = 7.9, J2′,3′ = 9.7 Hz, H-2′), 5.53 (d, 1
H, J1,2 = 3.6 Hz, H-1), 5.03 (d, 1 H, J1′,2′ = 7.9 Hz, H-1′), 4.84 (dd, 1
H, J5′,6′a = 3.6, J6′a,6′b = 11.9 Hz, H-6′a), 4.42 (dd, 1 H, J5′,6′b = 4.3,
J
3,4 = J 4,5 = 9.6 Hz, H-4c), 5.46 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.6 Hz, H-
2b), 5.42 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.6 Hz, H-2c), 4.97 (d, 1 H,
J
1,2 = 7.9 Hz, H-1b), 4.96 (d, 1 H, J1,2 = 7.9 Hz, H-1c), 4.85 (dd, 1 H,
J3,4 = J4,5 = 9.5 Hz, H-4a), 4.67–4.59 (m, 3 H), 4.50–4.37 (m, 2 H),
4.19–4.02 (m, 4 H), 3.91(dd, 1 H), 3.69 (dd, 1 H), 1.94, 1.78 (2 s, 6
H, 2 CH3CO).
Anal. Calcd for C80H68Cl3NO26: C, 61.37; H, 4.38. Found: C, 61.53;
H, 4.41.
6-O-Acetyl-2,3,4-tri-O-benzoyl-D-glucopyranosyl-(1→6)-
[2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→3)]-1,2-O-
isopropylidene- -D-glucofuranose (14)
Using the same procedure as described for the preparation of 12
from 6 and 11, the trisaccharide 14 was prepared from 8 (73.3 g,
0.108 mol) and 11 (80 g, 0.1 mol); white amorphous solid; yield:
111.8 g (85%); [ ]D +18.6 (c = 1.1, CHCl3).
J6′a,6′b = 11.9 Hz, H-6′b), 4.41 (d, 1 H, J3,4 = 2.6 Hz, H-3), 4.24–4.23
(m, 2 H, H-2,5′), 4.16 (dd, 1 H, J3,4 = 2.6, J4,5 = 8.8 Hz, H-4), 4.02
(m, 1 H, H-5), 3.83 (dd, 1 H, J5,6a = 3.2, J6a,6b = 11.4 Hz, H-6a), 3.67
(dd, 1 H, J5,6b = 6.0, J6a,6b = 11.4 Hz, H-6b), 1.44, 1.09 [2 s,
C(CH3)2].
1H NMR (400 MHz, CDCl3): δ = 8.05–7.26 (m, 35 H, 7 PhH), 5.87
(dd, 1 H, J2,3 = J3,4 = 9.6 Hz, H-3b), 5.84 (dd, 1 H, J2,3 = J3,4 = 9.6
Hz, H-3c), 5.65 (dd, 1 H, J3,4 = J4,5 = 9.6 Hz, H-4b), 5.59 (dd, 1 H,
Anal. Calcd for C43H42O15: C, 64.66; H, 5.30. Found: C, 64.79; H,
5.25.
J
3,4 = J4,5 = 9.6 Hz, H-4c), 5.51 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.6 Hz, H-
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Efficient Syntheses of Oligosaccharides
495
2b), 5.43 (dd, 1 H, J1,2 = 7.9, J2,3 = 9.6 Hz, H-2c), 5.42 (d, 1 H,
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→6)-[2,3,4,6-
tetra-O-benzoyl- -D-glucopyranosyl-(1→3)]-2,4-di-O-acetyl- -
D-glucopyranosyl-(1→6)-2,3,4-tri-O-benzoyl- -D-glucopyrano-
syl-(1→6)-[2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl-
(1→3)]-2,4-di-O-acetyl- -D-glucopyranosyl-(1→6)-3-O-ben-
zoyl-1,2-O-isopropylidene- -D-glucofuranose (18)
The heptasaccharide 18 was prepared by coupling 17 (5 g, 1.77
mmol) with 3-O-benzoyl-1,2-di-O-isopropylidene- -D-glucofura-
nose (0.69 g, 3.09 mmol) under the same conditions as described for
the preparation of 12 from 6 and 11; yield: 4.6 g (86%); [ ]D +34.3
(c = 1.0, CHCl3).
13C NMR (100 MHz, CDCl3): δ = 169.58, 169.29 168.23, 168.15 (4
CH3CO), 165.95, 165.94, 165.94, 165.76, 165.72, 165.60,
165.55,165.50, 165.28, 165.25, 165.10, 165.07, 165.04, 165.01,
165.00, 164.93 (16 PhCO), 112.05 [C(CH3)2], 105.04, 101.23,
101.05, 100.96, 100.95, 100.58, 100.38 (7 C-1), 83.38, 82.20 (2 C-
3), 26.57, 26.11 [C(CH3)2], 20.78, 20.60, 20.50, 20.42 (4 CH3CO).
J
J
1,2 = 3.6 Hz, H-1a), 4.96 (d, 1 H, J1,2 = 9.6 Hz, H-1b), 4.93 (d, 1 H,
1,2 = 9.6 Hz, H-1c), 4.71–3.79 (m, 12 H), 2.05 (s, 3 H, CH3CO),
1.33, 1.05 [2 s, 6 H, C(CH3)2].
Anal. Calcd for C72H66O24: C, 65.75; H, 5.06. Found: C, 66.00; H,
5.03.
2,3,4-Tri-O-benzoyl- -D-glucopyranosyl-(1→6)-[2,3,4,6-tetra-
O-benzoyl- -D-glucopyranosyl(1→3)]-1,2-O-isopropylidene- -
D-glucofuranose (15)
AcCl (6 mL) was added to a solution of 14 (100 g, 0.076 mol) in
MeOH–CH2Cl2 (1:1, 1000 mL), and the mixture was kept at r.t. for
20 h. After neutralization and concentration, the residue was sub-
jected to column chromatography on silical gel (9 × 60 cm, 3000
mL) using petroleum ether–EtOAc (1.5:1) as eluent to give com-
pound 15 as a white amorphous solid; yield: 87.1 g (90%); [ ]D
+22.6 (c = 1.0, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 8.05–7.26 (m, 35 H, 7 PhH), 5.91
(dd, 1 H, J2,3 = J3,4 = 9.8 Hz, H-3b), 5.90 (dd, 1 H, J2,3 = J3,4 = 9.8
Hz, H-3c), 5.73 (dd, 1 H, J3,4 = J4,5 = 9.8 Hz, H-4b), 5.56 (dd, 1 H,
J3,4 = J4,5 = 9.8 Hz, H-4c), 5.54–5.42 (m, 3 H), 4.99 (d, 1 H,
Anal. Calcd for C165H148O56: C, 65.47; H, 4.93. Found: C, 65.31; H,
4.86.
-D-Glucopyranosyl-(1→6)-[ -D-glucopyranosyl-(1→3)]- -D-
glucopyranosyl-(1→6)- -D-glucopyranosyl-(1→6)-[ -D-glu-
copyranosyl-(1→3)]- -D-glucopyranosyl-(1→6)-D-glucopyra-
nose (1)
Compound 18 (3.5 g, 1.16 mmol) was dissolved in 80% AcOH (100
mL) and the mixture was refluxed for 6 h. Concentration of the mix-
ture followed by deacylation in an ammonia-saturated solution of
CH2Cl2–MeOH, 1:9 (200 mL) at r.t. After 24 h, the mixture was
concentrated to about 20 mL, then CH2Cl2 (150 mL) was added.
The resultant precipitate was filtered and washed with CH2Cl2 (4 ×)
to give the free heptasaccharide 1 as a white powder; yield: 1.2 g
(90% for two steps); [ ]D –25.0 (c = 0.1, H2O).
J
1,2 = 7.9 Hz, H-1b), 4.95 (d, 1 H, J1,2 = 7.9 Hz, H-1c), 4.75–3.77 (m,
12 H), 1.33, 1.05 [2 s, 6 H, C(CH3)2].
Anal. Calcd for C70H64O23: C, 66.03; H, 5.07. Found: C, 66.24; H,
5.10.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→6)-[2,3,4,6-
tetra-O-benzoyl- -D-glucopyranosyl-(1→3)]-2,4-di-O-acetyl- -
D-glucopyranosyl-(1→6)-2,3,4-tri-O-benzoyl- -D-glucopyrano-
syl-(1→6)-[2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl-
(1→3)]-1,2-O-isopropylidene- -D-glucofuranose (16)
The hexasaccharide 16 was prepared by coupling 13 (50 g, 0.032
mol) with 15 (40.7 g, 0.032 mol) under the same conditions as de-
scribed for the preparation of 12 from 6 and 11; yield: 71.9 g (84%);
[ ]D +26.6 (c = 1.0, CHCl3).
13C NMR (100 MHz, D2O): δ = 102.7, 102.6, 102.6, 102.4, 102.4,
102.1, 102.1 (7 C-1), 84.5, 84.3 (2 C-3).
ESMS for C42H72O36 (1153.01): 1152.00 [M – 1]+.
13C NMR (100 MHz, CDCl3): δ = 169.4, 168.2 (2 CH3CO), 112.2
[C(CH3)2], 105.0, 101.5, 101.1, 101.0, 100.9, 100.2 (6 C-1), 82.9,
82.5 (2 C-3), 26.6, 25.9 [C(CH3)2], 20.85, 20.51 (2 CH3CO).
Dodecyl 2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→6)-
[2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl-(1→3)]-2,4-di-O-
acetyl- -D-glucopyranosyl-(1→6)-2,3,4-tri-O-benzoyl- -D-glu-
copyranosyl-(1→6)-[2,3,4,6-tetra-O-benzoyl- -D-glucopyrano-
syl-(1→3)]-2,4-di-O-acetyl- -D-glucopyranosyl-(1→6)-2,3,4-tri-
O-benzoyl- -D-glucopyranoside (19)
The heptasaccharide 19 was prepared by coupling 17 (3.4 g, 1.87
mmol) with 10 (1.65 g, 2.5 mmol) under the same conditions as de-
scribed for the preparation of 12 from 6 and 11; yield: 3.67 g (87%);
[ ]D +30.7 (c = 1.0, CHCl3).
13C NMR (100 MHz, CDCl3): δ = 169.66, 169.48, 168.15, 168.09
(4 CH3CO), 101.27, 101.19, 101.04, 101.04, 100.97, 100.38, 100.38
(7 C-1), 78.51, 78.25 (2 C-3), 31.87, 29.61, 29.57, 29.53, 29.45,
29.38, 29.33, 29.32, 25.84, 22.64, 20.81, 20.73, 20.52, 20.52 (4
CH3CO), 14,08.
Anal. Calcd for C148H130O48: C, 66.41; H, 4.90. Found: C, 66.51; H,
4.86.
2,3,4,6-Tetra-O-benzoyl- -D-glucopyranosyl-(1→6)-[2,3,4,6-
tetra-O-benzoyl- -D-glucopyranosyl-(1→3)]-2,4-di-O-acetyl- -
D-glucopyranosyl-(1→6)-2,3,4-tri-O-benzoyl- -D-glucopyrano-
syl-(1→6)-[2,3,4,6-tetra-O-benzoyl- -D-glucopyranosyl-
(1→3)]-2,4-di-O-acetyl- -D-glucopyranosyl Trichloroacetimi-
date (17)
The hexasaccharide glycosyl donor 17 was prepared from 16 (18.1
g, 6.76 mmol) under the same conditions as described for the prep-
aration of the trisaccharide donor 13 from 12; yield: 13.6 g (70% for
four steps); [ ]D +33.1 (c = 1.0, CHCl3).
1H NMR (400 MHz, CDCl3): δ = 8.29 [s, 1 H, O(NH)CCl3], 7.90–
7.26 (m, 75 H, 15 PhH), 6.24 (d, 1 H, J1,2 = 3.5 Hz, H-1), 6.06, 5.92,
5.88, 5.71, 5.70, 5.69, 5.68, 5.47, 5.46, 5.45, 5.39, 5.37 (12 dd, 12
H), 5.01, 4.97, 4.88, 4.75 4.53 (5 d, J1,2 = 7.9 Hz, 5 H-1), 1.97, 1.96,
1.85, 1.77 (4 s, 12 H, 4 CH3CO).
13C NMR (100 MHz, CDCl3): δ = 169.84, 169.66 169.44, 169.04 (4
CH3CO), 166.04–163.25 (15 COPh), 160.16 (CCl3), 133.40–127.44
(90 C, 15 C6H5), 101.34, 100.96, 100.96, 100.65, 100.17, 95.1 (6 C-
1), 90.2 [O(NH)CCl3], 20.77, 20.48, 20.44, 20.21 (4 CH3CO).
Anal. Calcd for C188H176O58: C, 67.14; H, 5.27. Found: C, 67.36; H,
5.36.
Dodecyl -D-Glucopyranosyl-(1→6)-[ -D-glucopyranosyl-
(1→3)]- -D-glucopyranosyl-(1→6)- -D-glucopyranosyl-(1→6)-
[ -D-glucopyranosyl-(1→3)]- -D-glucopyranosyl-(1→6)- -D-
glucopyranoside (2)
Compound 19 (2.2 g, 0.97 mmol) was dissolved in an ammonia-sat-
urated solution of 1:9 CH2Cl2–MeOH (100 mL) at r.t. After 24 h,
the mixture was concentrated to about 10 mL, and then CH2Cl2 (100
mL) was added. The resultant precipitate was filtered and washed
with CH2Cl2 (4 ×) to afford 2 as a white solid; yield: 1.24 g (96%);
[ ]D –19.5 (c = 0.1, H2O).
Anal. Calcd for C151H130Cl3NO50: C, 63.30; H, 4.57. Found: C,
63.21; H, 4.61.
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Y. Yi et al.
PAPER
13C NMR (100 MHz, D2O): δ = 105.67, 105.64, 105.45, 105.41,
105.31, 105.21, 104.94 (7 C-1), 87.17, 87.03 (2 C-3), 34.20, 32.72,
32.34, 31.96, 31.68, 28.05, 24.94, 16.49.
Kvarnstrom, I.; Svansson, L. J. Carbohydr. Chem. 1988, 7,
389. (f) Hong, N.; Ogawa, T. Tetrahedron Lett. 1990, 31,
3179. (g) Lorentzen, P. J.; Helpap, B.; Lockhoff, O. Angew.
Chem., Int. Ed. Engl. 1991, 30, 1681. (h) Cheong, J.-J.;
Birberg, W.; Fugedi, P.; Pilloti, A.; Garegg, P. J.; Hong, N.;
Ogawa, T.; Hahn, M. G. The Plant Cell 1991, 3, 127.
(i) Hong, N.; Nakahara, Y.; Ogawa, T. Proc. Jpn. Acad., Ser.
B 1993, 69, 55; Chem. Abstr. 1993, 119, 226277.
(j) Yamada, H.; Harad, T.; Takahashi, T. J. Am. Chem. Soc.
1994, 116, 7919. (k) Nicolaou, K. C.; Winssinger, N.;
Pastor, J.; Derosse, F. J. Am. Chem. Soc. 1997, 119, 449.
(l) Plante, O. J.; Palmacci, E. R.; Seeberger, P. H. Science
2001, 291, 1523.
ESMS for C54H96O36 (1321.33): 1320.2 [M – 1]+.
Acknowledgment
This work was supported by the Beijing Natural Science Founda-
tion (6021004) and National Natural Science Foundation of China
(30070864), and by The Ministry of Science and Technology
(2001AA246014).
(6) Ning, J.; Yuetao, Y.; Kong, F. Tetrahedron Lett. 2002, 43,
5545.
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Synthesis 2003, No. 4, 491–496 ISSN 0039-7881 © Thieme Stuttgart · New York