A short route to malto-trisaccharide synthons: Synthesis of the branched nonasaccharide, 6?-α-maltotriosyl-maltohexaose

Article abstract of DOI:10.1055/s-2002-20038

A short route to phenyl 1-thio-β-maltotrioside derived building blocks and their use for the synthesis of the branched nonasaccharide, 6?-α-maltotriosyl-maltohexaose, is described. Instead of using glucose and maltose as starting materials, maltotriose wa

Full text of DOI:10.1055/s-2002-20038

418
PAPER
A Short Route to Malto-trisaccharide Synthons: Synthesis of the Branched
Nonasaccharide, 6 - -Maltotriosyl-maltohexaose
A
Short
R
oute to Mal
e
to-trisacch
n
ride Synthons Damager,a,c Carl Erik Olsen,b,c Birger Lindberg Møller,a,c Mohammed Saddik Motawia*a,c
a
b
c
Carbohydrate Chemistry Group at Plant Biochemistry Laboratory, Department of Plant Biology, The Royal Veterinary and Agricultural
University, 40 Thorvaldsensvej, 1871 Frederiksberg C, Copenhagen, Denmark
Department of Chemistry, The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, 1871 Frederiksberg C, Copenhagen,
Denmark
Center for Molecular Plant Physiology (PlaCe), The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, 1871 Frederiks-
berg C, Copenhagen, Denmark
Fax +4535283333; E-mail: mosm@kvl.dk
Received 8 October 2001; revised 8 November 2001
phy and for further investigation of the action of enzymes
involved in starch biosynthesis using compound 22 as a
substrate, more material was needed demanding a shorter
synthetic route. Here, we report a convenient route to
Abstract: A short route to phenyl 1-thio- -maltotrioside derived
building blocks and their use for the synthesis of the branched nona-
saccharide, 6 - -maltotriosyl-maltohexaose, is described. Instead
of using glucose and maltose as starting materials, maltotriose was
used and synthetically manipulated in a well designed strategy to chemical synthesis of three essential trisaccharide syn-
obtain phenyl O-(2,3,4,6-tetra-O-benzyl- -D-glucopyranosyl)-
(1 4)-O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3-di-
thons 9, 15, and 21 starting from maltotriose. These syn-
thons can be used in the synthesis of linear and branched
O-benzyl-1-thio- -D-glucopyranoside, phenyl O-(2,3,4,6-tetra-O-
complex oligosaccharides. The availability of these new
benzyl- -D-glucopyranosyl)-(1 4)-O-(2,3,6-tri-O-benzyl- -D-
synthons reduces the multi-step synthesis of 221 from 40
glucopyranosyl)-(1 4)-2,3,6-tri-O-benzyl-1-thio- -D-glucopyra-
to 23 steps (Figure 1).
noside and phenyl O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-
(1 4)-O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3,6-
tri-O-benzyl-1-thio- -D-glucopyranoside. The described methodol-
ogy has shortened multi-step synthesis of the desired branched non-
asaccharide from 40 to 23 steps. It has also provided maltotriose
derived building blocks that independently or in combination with
corresponding glucose or maltose derived building blocks permit
The synthetic strategy to obtain the desired glycosyl ac-
ceptor 9 from maltotriose (1) is shown in Scheme 1. 1,6-
Anhydro derivatives of D-glucopyranose and of di- and
trisaccharides including maltose, cellobiose, and malto-
triose are readily available from the parent saccharides4–6
synthesis of any desired part of the amylopectin or amylose mole- and are used as versatile synthons in carbohydrate chem-
istry.7–12 Per-O-acetylated 1- -linked pentachlorophenyl
cule.
glycosides are the best suited precursors for the synthesis
of the corresponding per-O-acetylated 1,6-anhydro sug-
ars.12,13 Further, phase transfer catalysis (PTC) has been
extensively used in the field of carbohydrate
chemistry2,14–16 in particular to achieve nucleophilic sub-
Key words: 1,3-benzodithiolan-2-ylium protecting group, carbo-
hydrates, glycosides, 6 - -maltotriosyl-maltohexaose, phase trans-
fer catalysis
One of the difficulties in oligosaccharide synthesis is in stitutions at the anomeric center of glycosyl halides using
obtaining stereoselective coupling of building blocks. A a wide variety of nucleophiles17 including aryloxides.18,19
second difficulty originates from the polyfunctionality of Therefore, maltotriose (1) was acetylated in a standard
carbohydrate oligomers, which necessitates the use of procedure using anhydrous sodium acetate and acetic an-
elaborate protective group chemistry if complex carbohy- hydride to obtain maltotriose hendecaacetate (2) as an
drates are to be synthesised. Therefore, facilitation of the
, -anomeric mixture ( : ratio, 1:4) in quantitative
chemical synthesis of a desired oligosaccharide may be yield.20 The hendecaacetate 2 was converted into the cor-
obtained by developing a new coupling procedure or by responding per-O-acetylated- maltotriosyl bromide12 us-
establishing a well designed building block strategy to ing a hydrogen bromide–acetic acid solution in acetic acid
shorten a multi-step route. Recently, we reported1 chemi-
dichloromethane and subsequently treated with pen-
cal synthesis of the branched nonasaccharide 6 - -mal- tachlorophenol under PTC conditions using tetrabutylam-
totriosyl-maltohexaose (22) in 40 steps from a combined monium hydrogen sulfate (TBAHS) as the catalyst to
set of glucose-1 and maltose-derived2 building blocks provide pentachlorophenyl glycoside derivative 3 in 76%
(Figure 1). The synthesised branched nonasaccharide 22 yield. Compound 3 was previously prepared in a different
was used for investigation of the action of starch synthase manner.12 Conversion of 3 to the 1,6-anhydro derivative 4
II3 involved in the biosynthesis of starch. To determine the was accomplished in 85% yield as previously described12
three-dimensional structure of 22 by X-ray crystallogra- using aqueous potassium hydroxide and subsequent
acetylation with acetic anhydride and anhydrous sodium
acetate. The 1,6-anhydro ring of compound 4 was cleaved
Synthesis 2002, No. 3, 18 02 2002. Article Identifier:
selectively using Hanessian’s reagent21 as reported by
1437-210X,E;2002,0,03,0418,0426,ftx,en;T09401SS.pdf.
Sakairi22 but using our described modification
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

PAPER
A Short Route to Malto-trisaccharide Synthons
419
Figure 1 The three phenyl 1-thio- -D- maltotrioside derived building blocks 9, 15, and 21 were synthesised from maltotriose as starting ma-
terial instead of a combination of glucose and maltose derivatives as previously described1 shortening the multi-step synthesis of 6´´´- -mal-
totriosyl-maltohexaose (22) from 40 to 23 steps.
procedure23 with phenylthio-trimethylsilane and zinc io- zodithiolan-2-yl derivative 10 into 11 was achieved by
dide to accomplish conversion of 4 to the phenyl thiogly- deacetylation using methanolic ammonia. Standard ben-
coside 5 in 90% yield. In the 1H NMR spectrum of 5, the zylation of 11 using benzyl bromide and sodium hydride
doublet at 4.80 with J = 10.1 Hz reflects the -anomeric in DMF provided 12 in 51% yield. Compound 8 and 12
proton. In the corresponding 13C NMR spectrum, the di- were independently treated with aqueous acetic acid re-
agnostic signal at 85.4 ppm reflects the -anomeric car- sulting in the desired building block 9 in 71% and quanti-
bon. Formation of the -anomer of 5 was not observed. tative yield, respectively. The overall yield for the four
The free hydroxyl group at the 6-position of 5 was then steps involved in the manipulation of 5, 10, 11, and 12 into
protected with a trityl group introduced by the use of compound 9 was calculated to be 51%. The parallel ap-
triphenylchloromethane in pyridine24 to afford 6 in 88% proach based on the use of the trityl group as protecting
yield. Deacetylation of the tritylated derivative 6 by treat- group gave an overall yield of 27%. The deacetylation and
ment with sodium methoxide in methanol resulted in 7 the benzylation methods reported for the two kind of pro-
(91% yield). Benzylation of 7 with benzyl bromide and tecting groups are different, but experiments using both
sodium hydride in THF in the presence of tetrabutylam- methods for each type of protecting group were made and
monium iodide (TBAI) afforded 8 in 48% yield. An alter- the method providing the highest yield is reported here.
native protection of the free OH group at the 6-position of Hence, the 1,3-benzodithiol-2-ylium group can be used as
5 was accomplished using 1,3-benzodithiol-2-ylium an alternative temporary protecting group.
(BDT) as protecting group. BDT is a well known protect-
The synthesis of the two desired building blocks 15 and 21
is outlined in Scheme 2. Thiophenolysis of maltotriose
ing group in nucleoside chemistry25 but has not previously
been employed in carbohydrate chemistry. Compound 10
hendecaacetate (2) with phenylthio-trimethylsilane using
was obtained in quantitative yield by treating 5 with 1,3-
BF3 Et2O as the promoter afforded the phenyl thioglyco-
side 13 in 70% yield. Minor amounts of the -anomer of
benzodithiol-2-ylium tetrafluoroborate in pyridine. A
stronger base like dimethylaminopyridine cannot be used
in the reaction since it activates 1,3-benzodithiol-2-ylium
13 (< 2%) were removed by chromatography. Although
13 is a known compound26 only its optical rotation has
tetrafluoroborate to form the dimer, dibenzotetrathiaful-
been reported. Neither its NMR data nor any other exper-
valene instead.25 Quantitative conversion of the 1,3-ben-
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I. Damager et al.
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the work up to obtain the 4 ,6 -O-benzylidene derivative
1
gave 18 in 64% yield. In the H NMR spectrum of 18, a
singlet at 5.47 reflects the benzylic proton. In the related
13C NMR spectrum, a signal at 101.6 ppm reflects the ben-
zylic carbon. Quantitative conversion of 18 into 19 was
achieved using sodium methoxide in methanol. Benzyla-
tion of 19 using benzyl bromide and sodium hydride re-
sulted in 20 (71% yield) after chromatographic
purification. Regioselective reductive cleavage of the
benzylidene function of 20 was achieved using sodium
cyanoborohydride, ethereal solution of hydrogen chlo-
ride, and ether in THF31 resulting in the desired building
block 21 in 43% yield with a free hydroxyl group at the C-
4 -position and a benzyl ether group at the C-6 -position.
The thioglycoside 5 is a glycosyl acceptor and was first
used in a coupling reaction with the glycosyl donor 171 us-
ing trimethylsilyl triflate (TMS triflate) as catalyst in an-
hydrous ether to provide the branched hexasaccharide 23
in 92% yield (Scheme 3). The acetyl groups of 23 were
easily removed using methanolic ammonia resulting in
quantitative yield of 24. However, numerous trials to ob-
tain the fully benzylated 25 were unsuccessful. Steric hin-
drance could be a likely explanation for incomplete
benzylation of the hexasaccharide. Therefore, we decided
to convert 5 into the analogue compound 9, which is pro-
tected with benzyl groups instead of acetyl groups, there-
by avoiding the troublesome benzylation of the
hexasaccharide.
Synthesis of the nonasaccharide, 6 - -maltotriosyl-mal-
tohexaose was smoothly carried out in 6 steps by coupling
of the three trisaccharide building blocks 9, 17, and 21 as
previously described.1
In conclusion, we have developed a more efficient and
convenient route to obtain the three phenylthio maltotrio-
side building blocks 9, 15, and 21 using maltotriose as the
starting material. The phenylthio group was chosen for
two main reasons. First, thioglycosides are relatively sta-
ble to conditions used for manipulating other protecting
groups and second, the phenylthio group can easily be re-
moved.32 The 1,3-benzodithiolan-2-yl group was shown
to be a useful temporary protecting group in carbohydrate
chemistry and it can be an alternative to the trityl group.
The three building blocks 9, 15, and 21 were used for syn-
thesis of the branched nonasaccharide, 6 - -maltotriosyl-
maltohexaose, but may equally well be used as versatile
building blocks in the chemical synthesis of other com-
plex carbohydrates.
Scheme 1 Reagents and conditions: a) Ac2O, CH3COONa, 170 °C,
1 h; b) i. 33% HBr–HOAc, CH2Cl2–HOAc, 10 15 °C, 5 h ii. penta-
chlorophenol, TBAHS, EtOAc, 1 M aq Na2CO3, r.t., 18 h; c) i. 4 M aq
KOH, 120 °C, 20 h ii. 3 M H2SO4 iii. Ac2O, CH3COONa, 170 °C, 2.5
h;12 d) PhSSi(CH3)3, ZnI2, r.t., 17 h; e) TrCl, pyridine, 140 °C, 1 h; f)
NaOMe–MeOH, THF, r.t., 3 h; g) BnBr, TBAI, THF, NaH, r.t., 40 h
h) CH3COOH, H2O, 100 °C, 10 min; j) 1,3-benzodithiolan-2-ylium
tetrafluoroborate, pyridine, r.t., 1.5 h; k) 2 M NH3–MeOH, r.t., over-
night; l) BnBr, DMF, NaH, r.t., 24 h.
imental details have been reported. Deacetylation of 13
using sodium methoxide in methanol gave 14 in quantita-
tive yield. Reaction of 14 with benzyl bromide and sodi-
um hydride afforded the desired building block 151 in
79% yield. The other desired building block 21 was suc-
cessfully obtained from 14 (Scheme 2). Cyclic acetals
constitute one of the most useful derivatives for regiose-
lective O-protection in carbohydrate chemistry23,27–30 and
is used in the present strategy. The best results were ob-
tained using , -dibromotoluene in pyridine.2,27,28,30 Ben-
zylidenation of 14 under base catalysed conditions using
, -dibromotoluene in pyridine and subsequent in situ
acetylation using acetic anhydride in pyridine to facilitate
Melting points were determined using a Mettler FP81 MBC cell
connected to a Mettler FP80 Central Processor unit. Optical rota-
tions were measured at either 27 °C 1 °C with an Optical Activity
Ltd AA-1000 Polarimeter or at 23 °C 1 °C with an Optical Activ-
ity Ltd AA-10 Polarimeter. All reactions were monitored by TLC
on aluminium sheets coated with silica gel 60F254 (0.2 mm thick-
ness, E. Merck, Darmstadt, Germany) and reactants and products
were visualised by charring with 10% H2SO4 in MeOH. Column
chromatography was carried out using silica gel (particle size
0.040 0.063 mm, 230 400 mesh ASTM, E. Merck) and stepwise
elution with the solvent mixtures known from TLC chromatography
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A Short Route to Malto-trisaccharide Synthons
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Scheme 2 Reagents and conditions: a) PhSSi(CH3)3, BF3 Et2O, CH2Cl2, r.t., 16 h; b) NaOMe–MeOH, r.t.; c) BnBr, DMF, NaH, r.t.; d) NBS,
acetone water, r.t., 5 min;1 e) CCl3CN, K2CO3, CH2Cl2, r.t., 23 h;1 f) i. , -dibromotoluene, pyridine, 140 °C, 2 h. ii. Ac2O, r.t., 19 h; g)
NaBH3CN, THF, 4 Å MS, HCl–Et2O, 0 °C, 20 min.
1H NMR (CDCl3): = 2.00, 2.00, 2.01, 2.02, 2.03, 2.04, 2.06, 2.10,
2.11, 2.16, 2.17 (11 s, 33 H, 11 COCH3), 3.88 (m, 1 H, H-5), 3.92
3.97 (m, 3 H, H-4´, H-5´, H-5´´), 4.01 (t, 1 H, J3,4 = J4,5 = 9.1 Hz, H-
4), 4.06 (dd, 1 H, J5´´,6´´a = 2.2 Hz, J6´´a,6´´b = 12.5 Hz, H-6´´a), 4.17
(dd, 1 H, J5´,6´b = 2.9 Hz, J6´a,6´b = 12.5 Hz, H-6´b), 4.25 (dd, 1 H,
J
5´´,6´´b = 3.4 Hz, H-6´´b), 4.31 (dd, 1 H, J5,6b = 4.2 Hz, J6a,6b = 12.5
Hz, H-6b), 4.45 (dd, 1 H, J5,6a = 2.6 Hz, H-6a), 4.47 (dd, 1 H,
5´,6´a = 2.0 Hz, H-6´a), 4.74 (dd, 1 H, J2´,3´ = 10.5 Hz, H-2´), 4.85
J
(dd, 1 H, J2´´,3´´ = 9.9 Hz, H-2´´), 4.97 (dd, 1 H, J2,3 = 9.1 Hz, H-2),
5.07 (t, 1 H, J3´´,4´´ = J4´´,5´´ = 9.9 Hz, H-4´´), 5.27 (d, 1 H, J1´,2´ = 4.0
Hz, H-1´), 5.30 (t, 1 H, H-3), 5.35 (t, 1 H, H-3´´), 5.39 (dd, 1 H,
Scheme 3 Reagents and conditions: a) TMS triflate, Et2O, 4 Å MS,
r.t., 1 h; b) 2 M NH3–MeOH, THF, r.t., overnight.
J3´,4´ = 10.5 Hz, H-3´), 5.46 (d, 1 H, J1´´,2´´ = 4.1 Hz, H-1´´), 5.75 (d,
1 H, J1,2 = 8.6 Hz, H-1).
13C NMR (CDCl3): = 20.5 (6 COCH3), 20.7 (4 COCH3), 20.8
(COCH3), 61.3 (C-6´´), 62.2 (C-6´), 62.6 (C-6), 67.8, 68.4, 69.0,
69.3, 70.0, 70.3, 70.9, 71.6, 72.4, 72.9, 73.4, 75.0 (C-2, C-3, C-4, C-
5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´), 91.2 (C-1),
95.6 (C-1´´), 95.8 (C-1´), 168.7 (C=O), 169.3 (C=O), 169.5 (2
C=O), 169.7 (C=O), 169.8 (C=O), 170.2 (C=O), 170.4 (2 C=O),
170.5 (2 C=O).
to permit separation of the individual components. Solvent extracts
1
were dried with anhyd MgSO4 unless otherwise specified. The H
NMR and 13C NMR spectra were recorded on a Bruker Advance
400 spectrometer. In D2O, dioxane was used as internal reference
[
H(dioxane) = 3.75; C(dioxane) = 67.4]. In CDCl3, acetone-d6 and
MeOH-d4, the H values are relative to internal Me4Si. In DMSO-d6
H value of 2.49 ppm was used as internal reference. The C-values
Anal. Calcd for C40H54O27 (966.85): C, 49.69; H, 5.63. Found: C,
49.52; H, 5.70.
a
are referenced to the solvent [ C(CDCl3) = 77.0; C(DMSO-
d6) = 39.4; C(MeOH-d4) = 49.0; C(acetone-d6) = 206 ppm]. Since
no 13C NMR data and no full 1H NMR assignment have been report-
ed for the known compounds 2, 3, and 4 they are reported here. FAB
spectra were recorded on a Jeol AX505W mass spectrometer. Mi-
croanalysis was performed at DBLab-Danish Bioprotein A/S, Sten-
huggervej 22, P.O. Box 829, DK-5230 Odense M, Denmark.
Pentachlorophenyl O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyrano-
syl)-(1 4)-O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-
2,3,6-tri-O-acetyl- -D-glucopyranoside (3)
To a stirred soln of 2 (10.00 g, 10.30 mmol) in CH2Cl2 HOAc (75
mL, 2:1) was added dropwise HBr (6.5 mL, 33 wt% soln in HOAc)
at 15 °C (acetone-ice bath). Stirring was continued at 10 15 °C
for 5 h, the solvent was evaporated first and the residue coevaporat-
ed with toluene (3 100 mL). To a stirred soln of the residue in
EtOAc (200 mL) was added tetrabutylammonium hydrogen sulfate
(4.00 g, 11.78 mmol), pentachlorophenol (14.00 g, 52.56 mmol)
dissolved in the minimum amount of EtOAc and 1 M aq Na2CO3
(200 mL). The mixture was vigorously stirred at r.t. for 18 h. The
organic phase was separated and washed with H2O (3 200 mL), 1
M aq NaOH (200 mL), H2O (3 × 200 mL), brine (3 200 mL), then
dried and evaporated. The residue was chromatographed on silica
gel (210 g) with Et2O pentane (3:2) to remove all impurities. Elu-
tion with Et2O afforded compound 3, which was crystallised from
EtOH as white crystals (9.18 g, 76%): mp 116.2 °C, Lit.12 mp 109
112 °C.
Maltotriose Hendecaacetate (2)
Maltotriose (25 g, 49.56 mmol) was added in three portions to a
stirred mixture of anhyd NaOAc (25 g) and Ac2O (250 mL) at re-
flux. Stirring was continued for 1 h at reflux after which the reaction
mixture was cooled. and the solvent evaporated. The residue was
coevaporated with toluene (3 200 mL) and dissolved in EtOAc
(400 mL). The organic phase was washed with H2O (3 400 mL),
sat. aq NaHCO3 (300 mL), brine (300 mL), and then dried. The sol-
vent was evaporated and the residue was coevaporated with toluene
(3 200 mL) to afford 2 as a white solid as an , anomeric mixture
(1:4) in quantitative yield (47.72 g). The anomer was crystallised
from EtOH to afford white crystals; mp 136.1 °C, Lit.33 134 136 °C
[ ]D27 +87.4 (c = 0.53, CHCl3), Lit.33 [ ]D25 +89.5 (c = 2.9, CHCl3).
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I. Damager et al.
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23
23
[ ]D +116.4 (c = 0.08, CHCl3), Lit.12 [ ]D +114 (c = 0.63,
Phenyl O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-acet-
yl-1-thio- -D-glucopyranoside (5)
CHCl3).
1H NMR (CDCl3): = 2.00, 2.00, 2.03, 2.03, 3.03, 2.04, 2.08, 2.10,
2.11, 2.16 (10 s, 30 H, 10 COCH3), 3.67 (m, 1 H, H-5), 3.89 3.96
(m, 3 H, H-4´, H-5´, H-5´´), 4.05 (dd, 1 H, J5´´,6´´a = 2.0 Hz, J6´´a,
6´´b = 12.3 Hz, H-6´´a), 4.09 (t, 1 H, J3,4 = J4,5 = 9.7 Hz, H-4), 4.18
(dd, 1 H, J5´,6´b = 2.3 Hz, J 6´a,6´b = 12.3 Hz, H-6´b), 4.24 (dd, 1 H,
J5´´,6´´b = 3.7 Hz, H-6´´b), 4.29 (dd, 1 H, J5,6b = 4.3 Hz, J6a,6b, = 12.3
Hz, H-6b), 4.41 (dd, 1 H, J5,6a = 3.3 Hz, H-6a), 4.46 (bd, 1 H, H-
6´a), 4.74 (dd, 1 H, J2´,3´ = 10.7 Hz, H-2´), 4.85 (dd, 1 H,
To a stirred soln of 4 (18.34 g, 21.21 mmol) in anhyd CH2Cl2 (400
mL) was added phenylthio-trimethylsilane (24 mL, 127.26 mmol),
zinc iodide (40.62 g, 127.26 mmol) and stirring was continued at r.t.
for 17 h. The reaction mixture was filtered through a pad of sea sand
over a silica gel layer. To the filtrate was added solid NaHCO3 (15
g), the solvent was evaporated and the residue obtained was dis-
solved in EtOAc (400 mL) and sat. aq NaHCO3 (300 mL). The or-
ganic phase was separated and washed with 1 M aq NaOH (300
mL), water (3 × 300 mL), and brine (300 mL), then dried and evap-
orated. The residue was chromatographed on silica gel (320 g) with
Et2O pentane (4:1) as eluent to remove all impurities. Elution with
Et2O afforded compound 5, which crystallised from EtOH as white
crystals (18.69 g, 90%): mp 141.1 °C.
J
2´´,3´´ = 10.7 Hz, H-2´´), 5.07 (t, 1 H, J3´´4´´ = J4´´,5´´ = 10.3 Hz, H-
4´´), 5.23 (dd, 1 H, J2,3 = 8.5 Hz, H-2), 5.27 (d, 1 H, J1,2 = 7.9 Hz,
H-1), 5.31 (d, 1 H, J1´,2´ = 4.3 Hz, H-1´), 5.34 (dd, 1 H, H-3), 5.35
(dd, 1 H, H-3´´), 5.37 (t, 1 H, J3´,4´ = 10.7 Hz, H-3´), 5.41 (d, 1 H,
J1´´,2´´ = 4.3 Hz, H-1´´).
13C NMR (CDCl3): = 20.5 (3 COCH3), 20.6 (2 COCH3), 20.8
(3 COCH3), 20.9 (2 COCH3), 61.4 (C-6´´), 62.2 (C-6), 62.3 (C-
6´), 67.9, 68.5, 69.0, 69.3, 70.0, 70.4, 71.7, 72.2, 72.3, 72.5, 73.5,
74.9 (C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´,
C-5´´), 95.6, 95.7, 100.3 (C-1, C-1´, C-1´´), 128.6 (2 Ar-C), 130.6
(Ar-C), 132.0 (2 Ar-C), 147.8 (Ar-C), 169.4 (COCH3), 169.6
(COCH3), 169.7 (COCH3), 169.8 (COCH3), 170.1 (2 COCH3),
170.3 (COCH3), 170.5 (3 COCH3).
[ ]D23 +72.0 (c = 0.36, CHCl3).
1H NMR (CDCl3): = 1.98, 2.00, 2.00, 2.03, 2.04, 2.05, 2.06, 2.10,
2.15 (9 s, 27 H, 9 COCH3), 3.58 (m, 1 H, H-5), 3.85 (dd, 1 H,
J5,6b = 3.5 Hz, J6a,6b = 12.7 Hz, H-6b), 3.86 3.98 (m, 3 H, H-4´, H-
5´, H-5´´), 4.01 (dd, 1 H, J5,6a = 2.4 Hz, H-6a), 4.05 (dd, 1 H,
J
J
5´´,6´´a = 2.5 Hz, J6´´a,6´´b = 12.7 Hz, H-6´´a), 4.08 (t, 1 H,
3,4 = J4,5 = 9.4 Hz, H-4), 4.20 4.28 (m, 2 H, H-6´b, H-6´´b), 4.47
(dd, 1 H, J5´,6´a = 2.0 Hz, J6´a,6´b = 12.3 Hz, H-6´a), 4.71 (dd, 1 H,
2´,3´ = 10.4 Hz, H-2´), 4.79 (t, 1 H, J2,3 = 10.1 Hz, H-2), 4.80 (d, 1
Anal. Calcd for C44H51Cl5O26 (1173.14): C, 45.05; H, 4.38. Found:
C, 44.86; H, 4.51.
J
H, J1,2 = 10.1 Hz, H-1), 4.85 (dd, 1 H, J2´´,3´´ = 10.4 Hz, H-2´´), 5.06
(t, 1 H, J3´´,4´´ = J4´´,5´´ = 10.2 Hz, H-4´´), 5.31 (d, 1 H, J1´,2´ = 4.1 Hz,
H-1´), 5.33 (dd, 1 H, H-3), 5.37 (t, 1 H, J3´,4´ = 10.4 Hz, H-3´), 5.38
(t, 1 H, H-3´´), 5.40 (d, 1 H, J1´´,2´´ = 4.1 Hz, H-1´´), 7.33 7.48 (m,
5 H, Ar-H).
O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyranosyl)-(1 4)-O-(2,3,6-
tri-O-acetyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-acetyl-1,6-
anhydro- -D-glucopyranose (4)
A stirred suspension of 3 (9.18 g, 7.83 mmol) in 4 M aq KOH (50
mL) was refluxed at 120 °C for 20 h. The mixture was cooled to 0
°C, neutralised with 3 M H2SO4 and filtered. The filtrate was evap-
orated first and then coevaporated with toluene (3 50 mL). The
residue obtained was refluxed at 170 °C for 2.5 h with anhyd
NaOAc (9 g) and Ac2O (90 mL). The mixture was cooled to r.t.,
evaporated first, then the residue coevaporated with toluene (3 50
mL). The residue was dissolved in EtOAc (200 mL) and sat. aq
NaHCO3 (150 mL). The organic phase was separated and washed
with 1 M aq NaOH (15 mL), H2O (15 mL) and brine (15 mL), then
dried and evaporated. The residue was chromatographed on silica
gel (210 g) with CHCl3 EtOAc (1:1) as eluent to afford 4, which
crystallised from EtOH as white crystals (5.74 g, 85%): mp 155.0
°C, Lit.12 mp 159 161 °C, Lit.34 mp 156.5 157 °C.
13C NMR (CDCl3): = 20.9 (COCH3), 21.0 (COCH3), 21.1 (4
COCH3), 21.2 (COCH3), 21.3 (COCH3), 22.7 (COCH3), 61.8, 61.8,
63.1 (C-6, C-6´, C-6´´), 68.0, 68.4, 68.7, 69.4, 69.9, 70.6, 70.9, 71.0,
71.8, 72.5, 76.4, 78.5 (C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-
2´´, C-3´´, C-4´´, C-5´´), 85.4 (C-1´), 95.2, 95.6 (C-1, C-1´´), 128.8
(Ar-C), 129.5 (2 Ar-C), 132.1 (Ar-C), 133.2 (2 Ar-C), 169.9 (2
C=O), 170.1 (C=O), 170.3 (C=O), 170.6 (C=O), 170.9 (2 C=O),
171.0 (2 C=O).
Anal. Calcd for C42H54O24S (974.93): C, 51.74; H, 5.58; S, 3.29.
Found: C, 51.33; H, 5.63; S, 3.46.
Phenyl O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-
acetyl-6-O-(triphenylmethyl)-1-thio- -D-glucopyranoside (6)
To a stirred soln of 5 (12.00 g, 12.3 mmol) in anhyd pyridine (100
mL) was added triphenylchloromethane (34.3 g, 61.5 mmol). The
mixture was refluxed at 140 °C for 1 h with exclusion of moisture
by fitting a CaCl2 tube on top of the condenser. The solvent was
evaporated and the residue was coevaporated with toluene (3 100
mL). The residue was chromatographed on silica gel (320 g) with
pentane and Et2O–pentane (4:1) afforded 6¸ which crystallised from
EtOH as white crystals (13.12 g, 88%): mp 155.1 °C.
[ ]D27 +83.2 (c = 0.38, CHCl3), Lit.12 [ ]D23 +89 (c = 0.46, CHCl3),
Lit.34 [ ]D15 +82.4 (c = 1.5, CHCl3).
1H NMR (CDCl3): = 2.00, 2.01, 2.03, 2.04, 2.04, 2.10, 2.10, 2.13,
2.21 (9 s, 27 H, COCH3), 3.48 (br s, 1 H, H-4), 3.81 (dd,1 H,
J5,6a = 5.3 Hz, J6a,6b = 7.6 Hz, H-6a), 3.96 4.03 (m, 3 H, H-6b, H-
4´, H-5´´), 4.06 (dd, 1 H, J5´´,6´´a = 2.3 Hz, J6´´a,6´´b = 12.3 Hz, H-
6´´a), 4.22 (dd, 1 H, J5´,6´b = 3.8 Hz, J6´a,6´b = 12.6 Hz, H-6´b), 4.25
(dd, 1 H, J5´´,6´´b = 3.5 Hz, H-6´´b), 4.40 (dt, 1 H, J5´,6´a = 2.6 Hz,
J4´,5´ = 9.9 Hz, H-5´), 4.51 (dd, 1 H, H-6´a), 4.60 (br s, 1 H, H-2),
4.72 (dd, 1 H, J2´,3´ = 10.2 Hz, H-2´), 4.78 (bd, J5,6b = 5.3 Hz, H-5),
4.84 (t, 1 H, J2,3 = J3,4 = 1.5 Hz, H-3), 4.89 (dd, 1 H, J2´´,3´´ = 10.5
Hz, H-2´´), 5.08 (t, 1 H, J3´´,4´´ = 9.7 Hz, J4´´,5´´ = 9.9 Hz, H-4´´),
5.19 (d, 1 H, J1´,2´ = 3.8 Hz, H-1´), 5.37 (dd, 1 H, H-3´´), 5.42 (d, 1
H, J1´´,2´´ = 3.8 Hz, H-1´´), 5.50 (br s, 1 H, H-1), 5.57 (dd, 1 H,
[ ]D23 +80.0 (c = 0.24, CHCl3).
1H NMR (CDCl3): = 1.95, 1.96, 1.98, 2.00, 2.02, 2.06, 2.09, 2.09,
2.11 (9 s, 27 H, 9 COCH3), 3.32 3.40 (m, 2 H, H-5, H-5´), 3.48
3.53 (m, 2 H, H-6a, H-6b), 3.65 3.82 (m, 4 H, H-4, H-4´, H-5´´, H-
6´b), 3.89 (dd, 1 H, J5´,6´a = 2.0 Hz, J6´a,6´b = 12.1 Hz, H-6´a), 4.02
(dd, 1 H, J5´´,6´´a = 2.3 Hz, J6´´a,6´´b = 12.5 Hz, H-6´´a), 4.25 (dd, 1 H,
J5´´,6´´b = 3.4 Hz, H-6´´b), 4.63 (dd, 1 H, J2´,3´ = 10.5 Hz, H-2´), 4.73
(d, 1 H, J1,2 = 10.1 Hz, H-1), 4.84 4.92 (m, 2 H, H-2, H-2´´), 4.99
(d, 1 H, J1´,2´ = 4.0 Hz, H-1´), 5.10 (t, 1 H, J3´´,4´´ = 9.8 Hz,
J3´,4´ = 9.1 Hz, H-3´).
13C NMR (CDCl3): 20.5 (4 COCH3), 20.6, 20.8 (3 COCH3),
20.9 (2 COCH3), 61.3 (C-6´´), 62.7 (C-6´), 64.9 (C-6), 68.0 (C-
4´´), 68.3 (C-5´´), 68.4 (C-5´), 68.5 (C-2), 69.2 (C-3´´), 69.9 (C-2´´),
70.3 (C-3), 71.1 (C-2´), 72.2 (C-3´), 72.6 (C-4´), 74.2 (C-5), 76.7
(C-4), 95.7 (C-1´´), 96.8 (C-1´), 99.0 (C-1), 169.3 (2 C=O), 169.6
(C=O), 169.7 (C=O), 170.0 (C=O), 170.4 (3 C=O), 170.5 (C=O).
J4´´,5´´ = 10.4 Hz, H-4´´), 5.17 (dd, 1 H, J2,3 = J3,4 = 8.7 Hz, H-3),
5.19 (dd, 1 H, J3´,4´ = 9.0 Hz, H-3´), 5.38 (d, 1 H, J1´´,2´´ = 4.0 Hz, H-
1´´), 5.43 (dd, 1 H, J 2´´,3´´ = 9.8 Hz, H-3´´), 7.18 7.60 (m, 20 H, Ar-
H).
Synthesis 2002, No. 3, 418–426 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
A Short Route to Malto-trisaccharide Synthons
423
13C NMR (CDCl3): = 20.5 (3 COCH3), 20.6 (2 COCH3), 20.7
(2 COCH3), 20.9 (2 COCH3), 61.3 (C-6´´), 62.2 (C-6´), 64.0 (C-
6), 68.0 (C-4´), 68.4, 68.4 (C-5´, C-5´´), 69.5 (C-3´´), 69.7, 70.3 (C-
2, C-2´´), 70.9 (C-2´), 71.6 (C-4´), 72.1 (C-3´), 74.0 (C-4), 76.5 (C-
3), 77.8 (C-5), 85.9 (C-1), 87.2 (C(Ph)3), 95.4 (C-1´), 95.5 (C-1´´),
127.2 146.9 (Ar-C), 169.3 (C=O), 169.6 (C=O), 169.7 (C=O),
169.9 (C=O), 170.0 (C=O), 170.2 (C=O), 170.4 (C=O), 170.5
(C=O), 170.6 (C=O).
Phenyl O-(2,3,4,6-Tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-
benzyl-1-thio- -D-glucopyranoside (9)
A stirred soln of either 8 (296 mg, 0.18 mmol) or 12 (229 mg, 0.15
mmol) in HOAc (3 mL, 99.8%) was heated to 100 °C and H2O (2
mL) was added until the reaction mixture became turbid. HOAc was
then added to obtain clear soln and stirring continued for 10 min.
The mixture was evaporated and the residue coevaporated with tol-
uene (3 10 mL). The residue was chromatographed on silica gel
(30 g) with Et2O pentane (10:90 and 30:70 ) as eluent to give 91 as
colourless syrup in 71% yield from 8 and in quantitative yield from
12.
Anal. Calcd for C61H68O24S (1217.25): C, 60.19; H, 5.63; S, 2.63.
Found: C, 60.02; H, 5.74; S, 2.72.
Phenyl O-( -D-Glucopyranosyl)-(1 4)-O-( -D-glucopyranos-
yl)-(1 4)-6-O-(triphenylmethyl)-1-thio- -D-glucopyranoside
(7)
Phenyl O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-
acetyl-6-O-(1,3-benzodithiolan-2-yl)-1-thio- -D-
NaOMe (5 mL, 30% in MeOH) was added to a stirred soln of 6
(10.5 g, 8.63 mmol) in MeOH THF (21 mL, 2:1) at 0 °C and stir-
ring was continued at r.t. for 3 h. After neutralisation with Dowex
50W-X8 (H+ form, 200 400 mesh), the resin was filtered off and
washed with MeOH (3 50 mL). The residue was obtained upon
evaporation of the combined filtrates and then coevaporated with
toluene (3 100 mL). Chromatography on silica gel (60 g) with
CHCl3 MeOH (90:10) as eluent afforded 7 as a white solid (6.56 g,
91%). An analytical sample was obtained by crystallisation from
EtOH.
glucopyranoside (10)
To a stirred soln of 5 (3.0 g, 3.08 mmol) in anhyd CH2Cl2 (20 mL)
was added 1,3-benzodithiol-2-ylium tetrafluoroborate (2.26 g, 9.23
mmol) and pyridine (0.75 mL, 9.29 mmol) under N2 and stirring
was continued at r.t. for 1.5 h. Et3N (3 mL) was added and the mix-
ture was filtered through a pad of sea sand and a layer of silica gel.
The solvent was evaporated and the residue was dissolved in EtOAc
(25 mL). The organic phase was separated and successively washed
with sat. aq NaHCO3 (20 mL), H2O (3 × 20 mL) until neutral pH,
then with brine (20 mL), dried and evaporated. The residue was
chromatographed on silica gel (90 g) with CH2Cl2 EtOAc (9:1 and
7:3) as eluent to give 10 as a white solid in quantitative yield (3.47
g). An analytical sample was obtained by crystallisation from
EtOH.
[ ]D23 +65.3 (c = 0.23, MeOH).
1H NMR (MeOH-d4): = 3.01 3.87 (m, 18 H, skeleton protons),
4.76 (d, 1 H, J1,2 = 9.7 Hz, H-1), 5.08 (d, 1 H, J1´,2´ = 3.8 Hz, H-1´),
5.11 (d, 1 H, J1´´,2´´ = 3.9 Hz, H-1´´), 7.17 7.65 (20 H, Ar-H).
13C NMR (MeOH-d4): = 61.1, 62.8 (C-6´, C-6´´), 65.6 (C-6), 71.4,
72.8, 73.6, 73.6, 74.3, 74.6, 74.6, 75.1, 79.2, 79.8, 80.9, 81.0 (C-2,
C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´),
88.2 (C-1), 89.4 (C(Ph)3), 102.1, 103.3, (C-1´ C-1´´), 128.0 145.5
(Ar-C).
[ ]D23 +139.1 (c = 0.34, acetone).
1H NMR (acetone-d6): = 1.97, 1.98, 1.98, 2.00, 2.00, 2.01, 2.03,
2.05, 2.08 (9 s, 27 H, 9 COCH3), 3.86 3.96 (m, 4 H, H-4, H-5, H-
6a, H-6b), 4.01 4.12 (m, 4 H, H-4´, H-5´, H-5´´, H-6´´a), 4.18 (dd,
1 H, J5',6´b = 3.6 Hz, J6´a,6´b = 12.2 Hz, H-6´b), 4.25 (dd, 1 H,
J5´´,6´´b = 4.1 Hz, J6´´a,6´´b = 12.7 Hz, H-6´´b), 4.41 (dd, 1 H,
Anal. Calcd for C43H50O15S.H2O (856.93): C, 60.27; H, 6.12; S,
3.74. Found: C, 59.85; H, 6.10; S, 3.85.
J5´,6´a = 1.5 Hz, H-6´a), 4.70 (dd, 1 H, J2´,3´ = 10.4 Hz, H-2´), 4.80
(dd, 1 H, J2,3 = 9.9 Hz, H-2), 4.88 (dd, 1 H, J2´´,3´´ = 10.6 Hz, H-2´´),
5.02 (d, 1 H, J1,2 = 9.9 Hz, H-1), 5.09 (t, 1 H, J3´´,4´´ = J4´´,5´´ = 9.9
Hz, H-4´´), 5.25 (d, 1 H, J1´,2´ = 3.9 Hz, H-1´), 5.33 (t, 1 H, J3,4 = 9.1
Hz, H-3), 5.39 (d, 1 H, J1´´,2´´ = 4.1 Hz, H-1´´), 5.39 (t, 1 H,
Phenyl O-(2,3,4,6-Tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-
benzyl-6-O-(triphenylmethyl)-1-thio- -D-glucopyranoside (8)
To a stirred soln of 7 (500 mg, 0.60 mmol) in anhyd THF (30 mL)
at 0 °C was added NaH (860 mg, 60% in mineral oil) under Ar and
stirring was continued at r.t. for 20 min. After addition of tetrabutyl-
ammonium iodide (4.10 g, 10.88 mmol), the reaction mixture was
cooled to 0 °C, BnBr (2.55 mL, 21.47 mmol) was added dropwise
and stirring was continued at r.t. for 40 h. After cooling to 0 °C and
addition of MeOH to decompose excess NaH, the soln was stirred
for an additional 10 min and then concentrated in vacuo. The mix-
ture was diluted with EtOAc (25 mL) and H2O (15 mL). The organ-
ic phase was washed with H2O (4 15 mL) and brine, then dried
and evaporated. The residue was chromatographed on silica gel (50
g) with pentane and Et2O pentane (1:9) as eluent and afforded 8 as
a colourless syrup (470 mg, 48%).
J3´,4´ = 10.4 Hz, H-3´), 5.43 (dd, 1 H, H-3´´), 7.08 (s, 1 H, SCHS),
7.18 7.40 (m, 9 H, Ar-H).
13C NMR (acetone-d6): = 20.5 (COCH3), 20.6 (3 COCH3), 20.7
(2 COCH3), 20.8 (COCH3), 21.0 (2 COCH3), 62.3 (C-6´´), 63.6
(C-6´), 64.8 (C-6), 69.1, 69.4, 69.9, 70.1, 70.8, 71.4, 71.4, 72.3, 73.6
, 74.1, 76.6, 77.9 (C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´,
C-3´´, C-4´´, C-5´´), 85.1 (C-1), 91.3 (SCHS), 96.2 (C-1´), 96.7 (C-
1´´), 122.8 136.9 (Ar-C), 169.8 (2 C=O), 170.2 (2 C=O), 170.4
(C=O), 170.6 (C=O), 170.7 (C=O), 170.9 (C=O), 171.0 (C=O).
Anal. Calcd for C49H58O24S3.H2O (1145.17): C, 51.39; H, 5.28; S,
8.40. Found: C, 51.10; H, 5.26; S, 8.07.
[ ]D23 +43.7 (c = 0.41, CHCl3).
Phenyl O-( -D-Glucopyranosyl)-(1 4)-O-( -D-glucopyranos-
yl)-(1 4)-6-O-(1,3-benzodithiolan-2-yl)-1-thio- -D-glucopyra-
noside (11)
Compound 10 (1.0 g, 0.89 mmol) was treated with methanolic NH3
(40 mL, 2.0 M). The mixture was stirred at r.t. overnight, evaporat-
ed and the residue coevaporated with toluene (3 25 mL). The res-
idue was suspended in CHCl3 and the solid product was filtered off
and washed with CHCl3 (3 20 mL) to give 11 in quantitative yield
(664 mg). An analytical sample of 11 was obtained by crystallisa-
tion MeOH as white crystals: mp 188 °C dec.
1H NMR (CDCl3): = 5.34 (d, 1 H, J1´,2´ = 4.1 Hz, H-1´), 5.70 (d, 1
H, J1´´,2´´ = 3.8 Hz, H-1´´), 7.00 7.72 (m, 65 H, Ar-H). H-1 was
overlapped by the signals from the methylene protons of the benzyl
groups.
13C NMR (CDCl3): = 63.9 (C-6), 68.0 (C-6´), 68.6 (C-6´´), 70.7,
70.9, 72.2, 74.7, 77.7, 78.4, 79.3, 79.6, 81.0, 81.7, 82.0 (C-2, C-4,
C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´), 73.1 (2
CH2Ph), 73.4 (2
CH2Ph), 73.8 (CH2Ph), 74.1 (CH2Ph), 74.8
(CH2Ph), 75.1 (CH2Ph), 75.4 (CH2Ph), 86.1 (C-3), 86.8 (C(Ph)3),
87.6 (C-1), 96.2 (C-1´), 97.2 (C-1´´), 126.3 143.9 (Ar-C).
[ ]D23 –144.7 ° (c = 0.15, DMSO).
Synthesis 2002, No. 3, 418–426 ISSN 0039-7881 © Thieme Stuttgart · New York

424
I. Damager et al.
PAPER
1H NMR (DMSO-d6): = 4.61 (d, 1 H, J1,2 = 9.6 Hz, H-1), 5.01 (d,
1 H, J1´,2´ = 3.7 Hz, H-1´), 5.01 (d, 1 H, J1´´,2´´ = 3.7 Hz, H-1´´), 6.85
(s, 1 H, SCHS), 7.10 7.50 (m, 9 H, Ar-H).
13C NMR (DMSO-d6): = 60.7, 61.0 (C-6´, C-6´´), 66.4 (C-6),
70.0, 72.0, 72.0, 72.1, 72.6, 73.3, 73.5, 73.7, 76.7, 77.6, 79.8, 79.8
(C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-
5´´), 86.8 (C-1), 90.6 (SCHS), 101.0, 101.1 (C-1´, C-1´´), 122.7
135.6 (Ar-C).
13C NMR (CDCl3): = 20.5 (4 COCH3), 20.6, (2 COCH3), 20.7
(COCH3), 20.8 (3 COCH3), 61.3, 62.3, 62.9 (C-6, C-6´, C-6´´),
67.9, 68.5, 68.9, 69.3, 70.0, 70.4, 70.6, 71.7, 72.4, 73.5, 76.0, 76.3
(C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-
5´´), 84.9, 95.6, 95.7 (C-1C-1´C-1´´), 128.4 (Ar-C), 128.8 (2 Ar-
C), 131.1 (Ar-C), 133.4 (Ar-C), 169.4 (C=O), 169.5 (C=O), 169.6
(C=O), 169.8 (C=O), 170.0 (C=O), 170.3 (2 C=O ), 170.4 (C=O),
170.5 (2 C=O ).
Anal. Calcd for C44H56O25S (1016.97): C, 51.97; H, 5.55; S, 3.15.
Found: C, 52.14; H, 5.62; S, 3.33.
MS (FAB): m/z = 771 [M+ + Na].
Phenyl O-(2,3,4,6-Tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3-di-O-
benzyl-6-O-(1,3-benzodithiolan-2-yl)-1-thio- -D-glucopyra-
noside (12)
Phenyl O-( -D-Glucopyranosyl)-(1 4)-O-( -D-glucopyranos-
yl)-(1 4)-1-thio- -D-glucopyranoside (14)
Compound 13 (10.13 g, 9.96 mmol) was deacetylated and worked
up as described for 7. Compound 14 was obtained after crystallisa-
tion from MeOH as white crystals in quantitative yield (5.94 g): mp
146.6 °C.
To a stirred soln of 11 (450 mg, 0.60 mmol) in anhyd DMF (10 mL)
at 0 °C was added NaH (1.21g, 60% in mineral oil) under N2 and
stirring was continued at r.t. for 1 h. The reaction mixture was
cooled to 0 °C and BnBr (3.6 mL diluted with 1 mL anhyd DMF)
was added dropwise. Stirring was continued at r.t. for 24 h. After
cooling to 0 °C and addition of MeOH to decompose excess NaH,
the soln was concentrated in vacuo and diluted with EtOAc (50 mL)
and H2O (25 mL). The organic phase was separated, washed with
H2O (4 25 mL), brine (25 mL), dried and evaporated. The residue
was chromatographed on silica gel (90 g) with Et2O pentane (2:8,
3:7 and 4:6 ) as eluent to afford 12 as a colourless syrup (409 mg,
51%): [ ]D23 +29.0 (c = 0.05, acetone).
[ ]D27 +133.3 (c = 0.29, H2O ).
1H NMR (DMSO-d6): = 3.08 3.75 (m, 18 H, skeleton protons),
4.67 (d, 1 H, J1,2 = 9.7 Hz, H-1), 5.01 (d, 1 H, J = 3.5 Hz, H-1,inter-
nal), 5.05 (d, 1 H, J = 3.5 Hz, H-1,internal), 7.23 7.48 (m, 5 H, Ar-
H).
13C NMR (DMSO-d6): = 60.4, 60.7, 61.0 (C-6, C-6´, C-6´´), 70.0,
71.9, 72.0 72.0, 72.5, 73.3, 73.3, 73.6, 77.8, 79.2, 79.4, 79.6 (C-2,
C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´),
86.9 (C-1), 100.6, 100.9 (C-1´, C-1´´), 126.9 (Ar-C), 129.2 (2 Ar-
C), 130.1 (2 Ar-C), 134.6 (Ar-C).
1H NMR (acetone-d6): = 5.53 (d, 1 H, J = 3.5 Hz, H-1,internal),
5.69 (d, 1 H, J = 3.7 Hz, H-1,internal), 7.18 7.60 (m, 54 H, Ar-H).
H-1 was overlapped by the signals from the methylene protons of
the benzyl groups.
Anal. Calcd for C24H36O15S.2H2O (632.63): C, 45.56; H, 6.37; S,
5.07. Found: C, 45.83; H, 6.32; S, 5.19.
13C NMR (acetone-d6): = 66.1 (C-6), 69.8, 70.4 (C-6´, C-6´´),
72.0, 72.1, 73.3, 74.4, 78.3, 78.9, 80.4, 80.9, 81.6, 82.1, 82.7 (C-2,
C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´), 73.4 (2
CH2Ph), 73.8 (2 CH2Ph), 74.3 (CH2Ph), 74.8 (CH2Ph), 75.3
(CH2Ph), 75.5 (CH2Ph), 75.9 (CH2Ph), 86.8 (C-3), 87.3 (C-1), 91.6
(SCHS), 96.9, 96.9 (C-1´, C-1´´), 123.0 140.1 (Ar-C).
Phenyl O-(2,3,4,6-Tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3,6-tri-O-
benzyl-1-thio- -D-glucopyranoside (15)
Compound 14 (3.30 g, 5.53 mmol) was benzylated and worked up
as described for 12. The residue was chromatographed on silica gel
(210 g) with Et2O pentane (3:7) as eluent to afford 15 as colourless
syrup (6.51g, 79%). Optical rotation and the 1H NMR and 13C NMR
spectral data were identical to literature data.1
Phenyl O-(2,3,4,6-Tetra-O-acetyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-2,3,6-tri-O-
acetyl-1-thio- -D-glucopyranoside (13)
Phenyl O-(2,3-Di-acetyl-4,6-O-benzylidene- -D-glucopyranos-
yl)-(1 4)-O-(2,3,6-tri-O-acetyl- -D-glucopyranosyl)-(1 4)-
2,3,6-tri-O-acetyl-1-thio- -D-glucopyranoside (18)
To a stirred soln of 2 (19.17 g, 19.82 mmol) and PhSSi(CH3)3 (6.0
mL, 31.18 mmol) in anhyd CH2Cl2 (50 mL) was added BF3 Et2O
(15 mL, 119.4 mmol) and stirring was continued at r.t. for 16 h un-
der Ar. Solid NaHCO3 (20 g) was added, the mixture was diluted
with EtOAc (300 mL), H2O (200 mL) and this mixture was stirred
for an additional 10 min. The organic phase was separated washed
with H2O (4 100 mL), NaOH (4 100 mL, 1 N), brine (100 mL),
dried and evaporated. The residue was chromatographed on silica
gel (320 g) with Et2O pentane (1:1 and 4:1) as eluent to afford 13,
which was crystallised from EtOH as white crystals (14.02 g, 70%):
mp 102.1 °C.
To a stirred soln of 14 (7.14 g, 12.10 mmol) in anhyd pyridine (50
mL) was added , -dibromotoluene (4 mL, 24.20 mmol) under Ar.
The reaction mixture was refluxed at 140 °C for 2 h with exclusion
of moisture by fitting a CaCl2 tube on top of the condenser. The
mixture was cooled to 0 °C, Ac2O (60 mL, 0.64 mol) was added and
stirred at r.t. for 19 h. The solvent was evaporated and the residue
coevaporated with toluene (3 100 mL), the residue was dissolved
in EtOAc (200 mL) and sat. aq NaHCO3 (150 mL) was added. The
organic phase was separated and washed with H2O until neutral pH,
then with brine (150 mL), dried and evaporated. The residue was
chromatographed on silica gel (200 g) with Et2O pentane (4:6) as
eluent to give 18, which was crystallised from EtOH as white solid
(7.97 g, 64%).
[ ]D27 +78.8 (c = 0.45, CHCl3).
1H NMR (CDCl3): = 1.97, 2.00, 2.00, 2.01, 2.03, 2.05, 2.06, 2.10,
2.15, 2.15 (10 s, 30 H, 10 COCH3), 3.76 (m, 1 H, H-5), 3.85 3.99
(m, 4 H, H-4, H-4´, H-5´, H-5´´), 4.05 (dd, 1 H, J5´´,6´´a = 2.4 Hz,
J6´´a,6´´b = 12.6 Hz, H-6´´a), 4.18 (dd, 1 H, J5´,6´b = 3.4 Hz,
[ ]D23 +28.6 ° (c = 0.14, CHCl3).
J
6´a,6´b = 12.3 Hz, H-6´b), 4.25 (dd, 1 H, J5´´,6´´b = 3.8 Hz, H-6´´b),
1H NMR (CDCl3): = 1.97, 2.01, 2.01, 2.04, 2.06, 2.06, 2.12, 2.15
(8 s, 24 H, 8 COCH3), 3.62 (t, 1 H, J3´´,4´´ = J4´´,5´´ = 9.9 Hz, H-4´´),
3.70 3.77 (m, 2 H, H-5, H-6´´), 3.83 (m, 1 H, H-5´´), 3.90 3.97 (m,
3 H, H-4, H-4´, H-5´), 4.17 4.32 (m, 3 H, H-6b, H-6´b, H-6´´), 4.52
(dd, 1 H, J5´,6´a = 1.6 Hz, J6´a,6´b = 12.5 Hz, H-6´a), 4.58 (dd, 1 H,
4.30 (dd, 1 H, J5,6b = 4.7 Hz, J6a,6b = 12.3 Hz, H-6b), 4.46 (dd, 1 H,
J5´,6´a = 2.1 Hz, H-6´a), 4.54 (dd, 1 H, J5,6a = 2.7 Hz,) H-6a), 4.73
(dd, 1 H, J2´,3´ = 10.1 Hz, H-2´), 4.73 (d, 1 H, J1,2 = 10.2 Hz, H-1),
4.76 (dd, 1 H, J2,3 = 8.7 Hz, H-2), 4.85 (dd, 1 H, J2´´,3´´ = 10.4 Hz, H-
2´´), 5.06 (dd, 1 H, J3´´,4´´ = 9.9 Hz, J4´´,5´´ = 10.1 Hz, H-4´´), 5.25 (d,
1 H, J1´,2´ = 4.1 Hz, H-1´), 5.29 (t, 1 H, J3,4 = 8.7 Hz, H-3), 5.35 (t, 1
H, H-3´´), 5.38 (t, 1 H, J3´,4´ = 10.1 Hz, H-3´), 5.40 (d, 1 H,
J5,6a = 2.7 Hz, J6a,6b = 12.3 Hz, H-6a), 4.72 (d, 1 H, J1,2 = 9.9 Hz, H-
1), 4.67 4.79 (m, 2 H, H-2, H-2´), 4.87 (dd, 1 H, J2´´,3´´ = 10.3 Hz,
H-2´´), 5.24 (d, 1 H, J1´,2´ = 4.3 Hz, H-1´), 5.29 (t, 1 H,
J2,3 = J3,4 = 8.6 Hz, H-3), 5.35 (d, 1 H, J1´´,2´´ = 4.1 Hz, H-1´´), 5.39
J1´´,2´´ = 4.1 Hz, H-1´´), 7.28 7.50 (m, 5 H, Ar-H).
Synthesis 2002, No. 3, 418–426 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
A Short Route to Malto-trisaccharide Synthons
425
(t, 1 H, J2´,3´ = J3´,4´ = 9.9 Hz, H-3´), 5.45 (t, 1 H, H-3´´), 5.47 (s, 1
H, OCHO), 7.26 7.51 (m, 10 H, Ar-H).
pad of sea sand over a silica gel layer. The filtrate was washed with
H2O (3 150 mL), sat. aq NaHCO3 (3 150 mL), H2O (3 150
mL), brine (150 mL), then dried and evaporated. The residue was
chromatographed on silica gel (80 g) with Et2O pentane (2:3) as
eluent to afford 21 as colorless syrup (760 mg, 43%). Optical rota-
tion, 1H NMR and 13C NMR spectral data were identical to literature
data.1
13C NMR (CDCl3): = 20.5 (COCH3), 20.6 (COCH3), 20.7 (2
COCH3), 20.8 (4 COCH3), 62.1 (C-6´), 62.7 (C-6), 63.7 (C-5´´),
68.4 (C-6´´), 68.4, 69.0, 70.4, 70.7, 70.8, 71.8, 72.4, 73.3, 76.1,
76.4, 78.7 (C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´,
C-4´´), 84.8 (C-1), 95.7 (C-1´), 96.4 (C-1´´), 101.6 (OCHO),
126.2 136.6 (Ar-C), 169.5 (C=O), 169.6 (2 C=O), 170.0 (C=O),
170.1 (C=O), 170.2 (C=O), 170.6 (C=O), 170.8 (C=O).
Phenyl O-(2,3,4,6-tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-O-(2,3,6-tri-
O-benzyl- -D-glucopyranosyl)-(1 6)-O-[(2,3,4,6-tetra-O-acet-
yl- -D-glucopyranosyl)-(1 4)-O-(2,3,6-tri-O-acetyl- -D-gluco-
pyranosyl)-(1 4)]-2,3-di-O-acetyl-1-thio- -D-glucopyranoside
(23)
Anal. Calcd for C47H56O23S.H2O (1039.02): C, 54.33; H, 5.63; S,
3.09. Found: C, 54.05; H, 5.71; S, 3.23.
Phenyl O-(4,6-O-Benzylidene- -D-glucopyranosyl)-(1 4)-O-( -
D-glucopyranosyl)-(1 4)-1-thio- -D-glucopyranoside (19)
Compound 18 (6.10 g, 5.97 mmol) was deacetylated and worked up
as described for 7 to give 19, which crystallised from EtOH as white
crystals in quantitative yield (4.09 g): mp 158.1 °C.
A soln of 5 (1.00 g, 1.03 mmol) and 171 (2.30 g, 1.48 mmol) in an-
hyd Et2O (35 mL) was stirred with 4 Å molecular sieves (0.5 g, ac-
tivated powder) under Ar at r.t. for 1 h. After cooling to 64 °C and
dropwise addition of trimethylsilyl trifluoromethanesulfonate (48
L, 0.26 mmol) in anhyd Et2O (20 mL) , stirring was continued for
1 h during which time the temperature was raised to r.t. After addi-
tion of solid NaHCO3 (1.5 g), the reaction mixture was stirred for
additional 10 min, diluted with EtOAc (30 mL) and filtered through
a pad of sea sand and a layer of silica gel. The filtrate was washed
with sat. aq NaHCO3 (25 mL), H2O (3 × 25 mL) until neutral pH,
brine (25 mL), dried and evaporated. The residue was chromato-
graphed on silica gel (95 g) with Et2O pentane (1:1 and 4:1 ) as elu-
ent to afford 23 as white foam (2.23 g, 92%). [ ]D23 +78.4 (c = 0.42,
CHCl3).
[ ]D23 +86.7 ° (c = 0.34, MeOH).
1H NMR (MeOH-d4): = 3.28 3.92 (m, 17 H, skeleton protons),
4.23 (dd, 1 H, J5´´6´´b = 4.7 Hz, J6´´a,6´´b = 9.9 Hz, H-6´´b), 4.62 (d, 1
H, J1,2 = 9.9 Hz, H-1), 5.18 (d, 1 H, J1´,2´ = 3.7 Hz, H-1´) 5.18 (d, 1
H, J1´´,2´´ = 3.7 Hz, H-1´´), 5.56 (s, 1 H, OCHO), 7.20 7.40 (m, 10
H, Ar-H).
13C NMR (MeOH-d4): = 62.3, 62.3 (C-6, C-6´), 69.8 (C-6´´), 65.0,
72.1, 73.3, 73.4, 73.7, 74.8, 74.9, 79.4, 80.6, 80.8, 81.8, 82.5 (C-2,
C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´, C-5´´),
89.3 (C-1), 102.5 (OCHO), 103.0, 103.5 (C-1´, C-1´´), 128.4 139.1
(Ar-C).
1H NMR (CDCl3): = 4.66 (d, 1 H, J1,2 = 9.9 Hz, H-1), 5.11 (d, 1
H, J = 3.8 Hz, H-1internal), 5.25 (d, 1 H, J = 3.8 Hz, H-1internal),
5.46 (d, 1 H, J = 3.8 Hz, H-1internal), 5.67 (d, 2 H, J = 3.8 Hz, H-
1internal).
Anal. Calcd for C31H40O15S.2H2O (720.74): C, 51.66; H, 6.15; S,
4.45. Found: C, 51.37; H, 6.02; S, 4.60.
13C NMR (CDCl3): = 85.2 (C-1), 95.2, 95.6, 96.2, 96.6, 96.7 (5 in-
ternal anomeric C).
Phenyl O-(2,3-di-Benzyl-4,6-O-benzylidene- -D-glucopyranos-
yl)-(1 4)-O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-
2,3,6-tri-O-benzyl-1-thio- -D-glucopyranoside (20)
A soln of 19 (500 mg, 0.73 mmol) in anhyd DMF (50 mL) was
stirred with NaH (467 mg, 60% in mineral oil) for 4 h at r.t. The
mixture was cooled to 0 °C, BnBr (1.5 mL) was added dropwise and
stirring was continued at r.t. for 5 d. The reaction mixture was
worked up as described for 12 and the residue was chromato-
graphed on silica gel (45 g) with Et2O pentane (1:4 and 1:1) as elu-
ent to afford 20 as colorless syrup (730 mg, 71%).
Anal. Calcd for C130H144O39S.3H2O (2416.65): C, 64.61; H, 6.26; S,
1.33. Found: C, 64.51; H, 6.24; S, 1.88.
Phenyl O-(2,3,4,6-Tetra-O-benzyl- -D-glucopyranosyl)-(1 4)-
O-(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-O-(2,3,6-tri-
O-benzyl- -D-glucopyranosyl)-(1 6)-O-[ -D-glucopyranosyl)-
(1 4)-O-( -D-glucopyranosyl)-(1 4)]-1-thio- -D-glucopyra-
noside (24)
The procedure was the same as described for 11 using 23 (1.62 g,
0.69 mmol) dissolved in THF (3 mL) and methanolic NH3 (50 mL,
2.0 M) to afford 24 as a white solid in quantitative yield (1.36 g).
[ ]D23 +19.7 (c = 0.30, DMSO).
1H NMR (DMSO-d6): = 4.68 (d, 1 H, J1,2 = 10.0 Hz, H-1), 4.94 (d,
1 H, J = 4.2 Hz, H-1internal), 4.97 (d, 1 H, J = 3.8 Hz, H-1internal),
5.02 (d, 1 H, J = 4.2 Hz, H-1internal), 5.50 (d, 2 H, J = 3.8 Hz, 2 H-
1internal).
[ ]D23 +2.75 ° (c = 1.09, CHCl3).
1H NMR (CDCl3): = 5.20 (d, 1 H, J = 3.5 Hz, H-1,internal), 5.30
(s, 1 H, OCHO), 5.66 (d, 1 H, J = 4.0 Hz, H-1,internal). 7.00 7.65
(m, 50 H, Ar-H). H-1 was overlapped by the signals from the me-
thylene protons of the benzyl groups.
13C NMR (CDCl3): = 63.2 (C-5´´), 68.7, 68.9, 68.9 (C-6, C-6´, C-
6´´), 70.6, 72.3, 73.5, 78.6, 78.8, 78.9, 79.5, 80.6, 81.6, 82.3, 86.5
(C-2, C-3, C-4, C-5, C-2´, C-3´, C-4´, C-5´, C-2´´, C-3´´, C-4´´),
73.1 (2 CH2Ph), 73.4 (CH2Ph), 73.5 (CH2Ph), 73.9 (CH2Ph), 74.4
(CH2Ph), 75.1 (CH2Ph), 75.2 (CH2Ph), 87.2 (C-1), 96.7, 97.4 (C-1´,
C-1´´), 101.1 (OCHO), 126.0 138.8 (Ar-C).
13C NMR (DMSO-d6): = 86.7 (C-1), 95.1 (2 C), 95.7, 96.2, 100.9,
101.2 (5 internal anomeric C).
Anal. Calcd for C112H126O30S.3H2O (2038.32): C, 66.00; H, 6.53; S,
1.57. Found: C, 66.26; H, 6.51; S, 1.98.
Phenyl O-(2,3,6-Tri-O-benzyl- -D-glucopyranosyl)-(1 4)-O-
(2,3,6-tri-O-benzyl- -D-glucopyranosyl)-(1 4)-2,3,6-tri-O-
benzyl-1-thio- -D-glucopyranoside (21)
Acknowledgements
A soln of 20 (1.77 g, 1.26 mmol) and NaBH3CN (1.20 g, 11.34
mmol) in anhyd THF (45 mL) containing 4 Å molecular sieves was
stirred at r.t. for 15 min. The mixture was cooled to 0 °C and a soln
of HCl in Et2O was gradually added until the soln became acidic
(pH 1 2). After additional stirring for 20 min at 0 °C, the reaction
mixture was diluted with EtOAc (100 mL) and filtered through a
This work was financially supported by the Danish National Rese-
arch Foundation, by the EU FAIR programme contract CT95-0568,
and by the Danish Directorate for Development (Non-food pro-
gram).
Synthesis 2002, No. 3, 418–426 ISSN 0039-7881 © Thieme Stuttgart · New York

426
I. Damager et al.
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Synthesis 2002, No. 3, 418–426 ISSN 0039-7881 © Thieme Stuttgart · New York