Synthesis of the trisaccharide and tetrasaccharide moieties of the potent immunoadjuvant QS-21

Article abstract of DOI:10.1002/ejoc.200300580

The title trisaccharide and tetrasaccharide moieties have been synthesized as part of our research programme to construct the complex triterpenoid saponin QS-21, a potent immunoadjuvant, which has been used in a series of clinical immunization trials. In view of the unwillingness of glucuronic acid as glycosyl acceptor, the branched glucuronic acid-containing trisaccharide 20 was synthesized from D-glucose, which was in turn glycosylated at positions 2 and 3, followed by oxidation at position 6, in a linear sequence of 15 steps and in good overall yield. The apiose-containing tetrasaccharide 36 was constructed by a linear glycosylation strategy from the non-reducing terminal sugar, D-apiose, which was prepared from D-xylose by a known procedure, also in a linear sequence of 15 steps. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.

Full text of DOI:10.1002/ejoc.200300580

FULL PAPER
Synthesis of the Trisaccharide and Tetrasaccharide Moieties of the Potent
Immunoadjuvant QS-21
Xiangming Zhu,*[a,b] Biao Yu,[a] Yongzheng Hui,[a] and Richard R. Schmidt[b]
Keywords: Carbohydrates / Glycosylation / Glycosides / Immunostimulants / Saponin / Trichloroacetimidates
The title trisaccharide and tetrasaccharide moieties have
followed by oxidation at position 6, in a linear sequence of
been synthesized as part of our research programme to con- 15 steps and in good overall yield. The apiose-containing
struct the complex triterpenoid saponin QS-21, a potent im-
munoadjuvant, which has been used in a series of clinical
immunization trials. In view of the unwillingness of glucu-
tetrasaccharide 36 was constructed by a linear glycosylation
strategy from the non-reducing terminal sugar, -apiose,
which was prepared from -xylose by a known procedure,
D
D
ronic acid as glycosyl acceptor, the branched glucuronic also in a linear sequence of 15 steps.
acid-containing trisaccharide 20 was synthesized from -glu- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
cose, which was in turn glycosylated at positions 2 and 3, Germany, 2004)
D
Introduction
saponins.[6,7] Here we present the synthesis of the trisacch-
aride[8] and tetrasaccharide moieties of the natural product.
QS-21,[1,2] an acylated bidesmosidic triterpenoid saponin
isolated from Quillaja saponaria Molina (Rosaceae), is a po-
tent immunoadjuvant that has been shown to enhance both
humoral and cell-mediated immune responses in a host of
vaccine formation assays.[3] A number of clinical trials with
QS-21 as an adjuvant have been performed, initially for
cancer vaccines (melanoma, breast and prostate) and sub-
sequently for infectious diseases (HIV-1, influenza, herpes,
malaria and hepatitis B).[4] It appears optimally effective as
an adjuvant for vaccines against pathogens that require a
potent cytotoxic T-lymphocyte response as an important
component of protective immunity. More than 1600 volun-
teers have been immunized with vaccines containing QS-21,
the most common side effect being pain/tenderness at the
injection site, which is dose-related and usually of short
duration.[4,5]
Structurally, QS-21 consists of a triterpene (quillaic acid)
with two attached sugar chains (one branched trisaccharide
and one unbranched tetrasaccharide) and a dimeric fatty
acyl group joined to the reducing terminal sugar of the
tetrasaccharide,[2] as shown in Figure 1. Attracted by its
amazing structure and promising bioactivities, we carried
out synthetic studies relating to the acylated triterpenoid
saponin after having accomplished the determination of the
absolute stereochemistry within the acyl moiety of quillaja
Results and Discussion
The trisaccharide moiety of QS-21 is composed of a β--
glucuronic acid residue connected at position 2 with a β--
galactose residue and at position 3 with a β--xylose resi-
due. The presence of a β--glucuronic acid residue linked
to another sugar in position 2 is common in a large variety
of natural products, especially saponins.[9] It is well docu-
mented that glycosylation of glucuronic acid derivatives
usually gives low product yields due to the electron-with-
drawing 5-carboxyl group,[10] which decreases the nucleo-
philicity of the hydroxy groups on glucuronide acceptors
remarkably. In view of this, an indirect but more conven-
tional strategy was applied to the synthesis of the trisacch-
aride fragment in question, the desired glucuronide being
prepared by introduction of the carboxyl group after coup-
ling with a glucopyranoside moiety.[11]
To carry out the synthetic scheme, glucoside 1 (All ϭ
Allyl) was prepared in 57% yield from -glucose by a
known procedure[12] and then selectively acylated with piva-
loyl chloride to give the desired 2-pivaloylated glucoside
2
[13] in 58% yield (Scheme 1). Silylation of 2 with tert-butyl-
dimethylsilyl chloride (TBS-Cl) followed by deacylation
with DIBAL-H smoothly provided an almost quantitative
yield of the sugar alcohol 4,[14] a potential glycosyl acceptor
in the subsequent glycosidation reaction. Unexpectedly,
however, the glycosylation of 4 with galactosyl trichloroace-
timidate 5[15] in the presence of catalytic amounts of
BF3·OEt2 gave the ortho ester 6 in 83% yield. A variety of
attempts to avoid this unwanted side reaction, including the
[a]
State Key Laboratory of Bio-organic and Natural Products
Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, Shanghai 200032, PR China
[b]
Fachbereich Chemie, Universität Konstanz,
Fach M 725, 78457 Konstanz, Germany
Fax: (internat.) ϩ49-7531-883135
E-mail: Richard.Schmidt@uni-konstanz.de
Eur. J. Org. Chem. 2004, 965Ϫ973
DOI: 10.1002/ejoc.200300580
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X. Zhu, B. Yu, Y. Hui, R. R. Schmidt
FULL PAPER
Figure 1. Molecular Structure of QS-21
duction of the desired products, so the thioglycosides 10a[22]
and 10b[23] were prepared and coupled with the above glu-
cosyl acceptors 4 and 7, as shown in Scheme 2. As antici-
pated, glycosylation of 4 with thioglycoside 10a with pro-
motion by NIS/AgOTf[24] smoothly generated the desired
disaccharide 11a in high yield (70%). Similarly, coupling of
sugar alcohols 4 and 7 with thioglycoside 10b also gave the
corresponding desired disaccharides 11b and 12, both in al-
most quantitative yields.
Scheme 1. Formation of ortho esters 6 and 8; reagents and con-
ditions: (a) PivCl, Py, 0 °C, 58%; (b) TBSCl, imidazole, DMAP,
DMF, 99%; (c) DIBAL-H, CH2Cl2, Ϫ78 °C, 98%; (d) BF3·Et2O
Scheme 2. Synthesis of Gal(1 Ǟ 2)Glc disaccharides; reagents and
˚
conditions: (a) NIS, AgOTf, 4 A molecular sieves, CH2Cl2, Ϫ20
°C, 11a (70%); 11b (97%); 12 (quant.)
˚
(cat.), 4 A molecular sieves, CH2Cl2, Ϫ50 °C, 6 (83%); 8 (92%)
The ready formation of disaccharides 11 and 12 was in
inverse procedure,[16] were unsuccessful, and surprisingly, sharp contrast with the above Schmidt glycosylation reac-
ortho ester 6 was readily formed under a variety of con- tions. The precise mechanistic details underlying the differ-
ditions.[17] Even TfOH-promoted (TfOH ϭ triflic acid) ent behaviour observed for trichloroacetimidate and thiog-
coupling between 4 and 5 also gave the ortho ester 6 in lycoside donors are not yet clear. With the disaccharide 11b
almost quantitative yield. A change of neighbouring group to hand, the synthetic scheme was then continued as shown
in the acceptor from TBS to PMB also did not bring about in Scheme 3. Desilylation of 11b with HFϪPy[25] furnished
the expected product, and similarly, ortho ester 8 was pro- the sugar alcohol 13 in 83% yield, and this was further gly-
duced in 92% yield by glycosylation of 7[18] with 5. To re- cosylated with peracetyl thioxyloside[26] in the presence of
duce the risk of ortho ester formation, per-benzoylated gal- NIS/AgOTf to afford the desired 2,3-branched trisaccharide
actosyl imidate 9[14] was prepared and treated with 4 or 7, 14, smoothly and in almost quantitative yield. Treatment of
as shown in Scheme 1. No coupling took place under the 14 with 80% HOAc gave the diol 15, which was selectively
normal Schmidt glycosidation conditions, however.[19,20]
tritylated and subsequently acetylated to produce sugar 16.
The above failure was attributed to steric hindrance of This was then subjected to detritylation, as shown in
the acceptors. From our experience in carbohydrate syn- Scheme 3, to give sugar 17, with one free hydroxy group at
thesis, we anticipated that the use of thioglycosides[21] in- position 6 of the glucose residue. The conversion of gluco-
stead of imidates as glycosyl donors should favour the pro- side 17 into the corresponding glucuronide 18 was effected
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Synthesis of Trisaccharide and Tetrasaccharide Moieties
FULL PAPER
Scheme 3. Synthesis of trisaccharide imidate 20; reagents and con-
˚
ditions: (a) HF/Py, 83%; (b) 1.2 equiv. donor, NIS, AgOTf, 4 A
molecular sieves, CH2Cl2, Ϫ20 °C, quant.; (c) 80% HOAc, 70 °C,
77%; (d) TrCl, Py, 80 °C; (e) Ac2O, Py, room temp., 92% (2 steps);
(f) 80% HOAc, 50 °C, 61%; (g) PDC, tBuOH, Ac2O, CH2Cl2, 90%;
(h) [Pd(PPh3)4], HOAc, 80 °C, 98%; (i) CCl3CN, DBU, CH2Cl2,
86%
Scheme 4. Synthesis of trisaccharide intermediate 26; reagents and
conditions: (a) Ac2O, Py, 82%; (b) NH3/THF/MeOH, 0 °C, 49%;
(c) CCl3CN, DBU, CH2Cl2, 98%; (d) 1.1 equiv. acceptor, 0.3 equiv.
˚
TMSOTf, 4 A molecular sieves, CH2Cl2, Ϫ4 °C, 72%; (e) H2, 10%
Pd/C, 1 atm, room temp.; (f) CCl3CN, DBU, CH2Cl2, 89% (2 steps);
˚
(g) 1.1 equiv. acceptor, 0.2 equiv. TMSOTf, 4 A molecular sieves,
by PDC oxidation[27] in the presence of tBuOH, and 18 was
produced in excellent yield (90%). Subsequently, treatment
of 18 with catalytic amounts of [Pd(PPh3)4][28] in the pres-
ence of HOAc produced the desired hemiacetal 19 in almost
quantitative yield, and this was smoothly further converted
CH2Cl2, Ϫ50 °C, 95%; (h) NaOMe, MeOH, 68%; (i) various con-
ditions, see: Ref.[34]; (j) Ac2O, Py, quant.; (k) Dowex 50 W (Hϩ);
for other conditions, see ref.[34]
To our surprise, however, the subsequent removal of the
into the trichloroacetimidate 20 in 86% yield. The trisacch- two isopropylidene groups from 26 failed under various
aride portion of QS-21 was thus furnished and ready for its conditions.[34] Under most conditions only compound 27
total synthesis.
was produced, which could be converted to trisaccharide 28
In view of the linear structure of the tetrasaccharide moi- by acetylation. The O-deisopropylidenation was also con-
ety of QS-21, we planned to construct it by a linear glycos- ducted on compound 24, but this also failed. Harsher con-
ylation strategy, by extending the sugar chain one by one ditions were also applied to the deacylated compound 29
from the non-reducing terminal sugar. In practice, the to cleave the isopropylidene groups, but only sugar 30 was
branched sugar 2,3-O-isopropylidene--apiofuranose 21 provided after acetylation, as a result of the extraordinary
was firstly prepared from -xylose in 21% overall yield by stability of the isopropylidene group at the apiose residue.
a literature procedure[29] and was subjected to acety-
The synthetic route therefore had to be modified as
lation,[30,31] followed by selective deacetylation to afford a shown in Scheme 5, and the cleavage of isopropylidene from
40% overall yield of the desired hemiacetal 22, which was apiose was carried out at an earlier stage in this scheme.
subsequently converted into apiosyl donor 23 by addition Disaccharide 31 was prepared by use of the fully acetylated
of CCl3CN. Under Schmidt glycosidation conditions,[20] apiosyl donor as described previously,[35] and converted
trichloroacetimidate 23 was coupled with pre-prepared xy- into trichloroacetimidate 32 by hydrogenation with H2, fol-
losyl acceptor[32] to give the desired disaccharide 24 in 72% lowed by treatment with CCl3CN. Compound 32 was then
yield, and this was then converted into the corresponding coupled with the same rhamnosyl acceptor as used above
imidate 25 in two steps by hydrogenation with H2 followed under Schmidt conditions to give the desired trisaccharide
by imidation with CCl3CN. Coupling of sugar 25 with the 33, which was treated with 80% HOAc and subsequently
pre-prepared rhamnosyl acceptor,[33] as shown in Scheme 4, acetylated to afford thioglycoside 34. Glycosylation of the
was performed in the presence of TMSOTf, affording the fourth sugar residue, allyl 3,4-O-isopropylidene-α--fucopy-
desired di-O-isopropylidenated trisaccharide 26 in excellent ranoside as acceptor,[36] with sugar 34 as glycosyl donor
yield (95%).
was performed in the presence of NIS/AgOTf, giving the
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967

X. Zhu, B. Yu, Y. Hui, R. R. Schmidt
FULL PAPER
PerkinϪElmer Model 2400 instrument. Yields refer to chromato-
graphically pure compounds and are calculated on the basis of re-
agents consumed.
˚
Ortho Ester 6: Freshly activated powdered molecular sieves (4 A, ഠ
1 g) were added to a solution of donor 5 (1.64 g, 3.32 mmol) and
acceptor 4 (1.23 g, 2.91 mmol) in CH2Cl2 (15 mL) under Ar and
the mixture was stirred at room temperature for 30 min, after which
it was cooled to Ϫ50 °C and boron trifluoride etherate (10 mg/mL
in CH2Cl2, 2.4 mL) was added dropwise. The reaction mixture was
allowed to warm to room temperature and stirred for 15 min. Et3N
was added to quench the reaction, and the mixture was filtered
through a pad of Celite and concentrated to give a residue, which
was purified by flash column chromatography (petroleum ether/
EtOAc, 7:1 Ǟ 5:1) to afford the title compound 6 (1.8 g, 83%) as
a white foam: [α]2D1 ϭ ϩ56.6 (c ϭ 0.45, CHCl3). 1H NMR
(300 MHz, CDCl3): δ ϭ 0.00 (s, 3 H), 0.06 (s, 3 H), 0.82 (s, 9 H),
1.70 (s, 3 H), 2.05 (s, 3 H), 2.07 (s, 3 H), 2.10 (s, 3 H), 3.43 (t, J ϭ
9.5 Hz, 1 H), 3.58 (dd, J ϭ 8.8, 3.6 Hz, 1 H), 3.69 (t, J ϭ 10.2 Hz,
1 H), 3.82 (m, 1 H), 3.98Ϫ4.34 (m, 8 H), 5.02 (m, 2 H), 5.19Ϫ5.36
(m, 2 H), 5.42 (t, J ϭ 2.6 Hz, 1 H), 5.48 (s, 1 H), 5.77 (d, J ϭ
4.7 Hz, 1 H), 5.94 (m, 1 H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ
170.5, 170.1, 169.8, 137.3, 133.1, 128.9, 128.1, 126.2, 121.8, 118.1,
101.9, 98.0, 97.2, 82.6, 75.0, 73.7, 71.3, 70.0, 69.0, 68.8, 68.6, 65.9,
62.2, 61.2, 25.8, 23.9, 25.6, 20.8, 20.7, 20.6, 18.3, Ϫ4.2, Ϫ4.6 ppm.
ESI MS: m/z ϭ 776 [M ϩ Naϩ], 792 [M ϩ Kϩ]. C36H52O15Si
(752.9): calcd. C 57.43, H 6.96; found C 57.43, H 7.00.
Scheme 5. Synthesis of tetrasaccharide 36; reagents and conditions:
(a) H2, 10% Pd/C, 50 atm, 40 °C; (b) CCl3CN, DBU, CH2Cl2, 33%
˚
(2 steps); (c) 1.3 equiv. acceptor, 0.2 equiv. TMSOTf, 4 A molecular
sieves, CH2Cl2, 88%; (d) 80% HOAc, 50 °C; (e) Ac2O, Py, 76% (2
˚
steps); (f) 1.2 equiv. acceptor, NIS, AgOTf, 4 A molecular sieves,
CH2Cl2, 91%; (g) I(CF2)8F, Na2S2O4, NaHCO3, CH3CN/H2O,
then Zn/NH4Cl, EtOH, reflux, 57%
Ortho Ester 8: The coupling of donor 5 (124 mg, 0.25 mmol) and
acceptor 7 (98 mg, 0.23 mmol) was performed in the same way as
described for 6 to give ortho ester 8 (160 mg, 92%) as a white foam:
[α]2D1 ϭ ϩ46.9 (c ϭ 0.96, CHCl3). 1H NMR (300 MHz, CDCl3):
δ ϭ 1.71 (s, 3 H), 2.06 (s, 6 H), 2.09 (s, 3 H), 3.78 (s, 3 H),
3.97Ϫ3.58 (m, 1 H), 4.31Ϫ4.01 (m, 8 H), 4.72 (AB peak, J ϭ
12.6 Hz, 2 H), 4.98 (d, J ϭ 3.6 Hz, 1 H), 5.03 (dd, J ϭ 9.6, 3.4 Hz,
1 H), 5.22Ϫ5.38 (m, 2 H), 5.41 (t, J ϭ 2.7 Hz, 1 H), 5.55 (s, 1 H),
5.77 (d, J ϭ 4.9 Hz, 1 H), 5.95 (m, 1 H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 170.4, 170.0, 169.8, 159.1, 137.3, 133.5, 130.7, 129.7,
128.9, 128.2, 126.0, 121.3, 118.3, 113.6, 101.2, 97.8, 97.5, 82.2, 75.1,
73.9, 73.4, 71.1, 69.0, 68.6, 65.8, 62.4, 61.3, 55.2, 23.9, 20.7,
20.5 ppm. EI MS: m/z ϭ 427, 331, 121. C38H46O16·0.5H2O (767.8):
calcd. C 59.45, H 6.17; found C 59.57, H 6.13.
tetrasaccharide 35 in 91% yield; chemoselective removal of
the 3a,4a-O-isopropylidene group should now enable the at-
tachment of the acyl side chain which is part of QS-21.
Compound 35 was further subjected to deallylation con-
ditions[37] to afford the sugar 36 in reasonable yield (57%),
ready for the transformation into a glycosyl donor.
In summary, the synthesis of the trisaccharide and tetra-
saccharide moieties of the potent immunoadjuvant QS-21
is reported. The trisaccharide portion, the glucuronic acid-
containing sugar 20, was constructed starting from -glu-
cose in a linear sequence in good overall yield. The tetrasac-
charide portion, the apiose-containing sugar 36, was syn-
thesized starting from -xylose in a linear sequence of 15
steps. Further work towards the completion of the synthesis
of QS-21 is in progress.[38]
Allyl
2,3,4,6-Tetra-O-acetyl-β-D-galactopyranosyl-(1Ǟ2)-4,6-O-
benzylidene-3-O-tert-butyldimethylsilyl-α-
D-glucopyranoside (11a):
A mixture of thioglycoside 10a (75 mg, 0.19 mmol), sugar alcohol
˚
4 (67 mg, 0.16 mmol) and powdered molecular sieves (4 A, 60 mg)
in CH2Cl2 (3 mL) was stirred at room temperature under Ar for
30 min and then cooled to Ϫ20 °C. NIS (54 mg, 0.24 mmol) was
added to this mixture, followed by the addition of a solution of
AgOTf (20 mg, 0.078 mmol) in toluene (0.2 mL). The reaction mix-
ture was allowed to warm slowly and stirred for 15 min after in-
itiation, and then quenched with Et3N. The suspension was diluted
with EtOAc and filtered through a pad of Celite, and the filtrate
was washed successively with 10% Na2S2O3 and water. The organic
layer was dried with MgSO4 and concentrated in vacuo to give a
residue, which was purified by flash column chromatography
(petroleum ether/EtOAc, 4:1) to give 11a (83 mg, 70%) as a white
foam: [α]2D0 ϭ ϩ28.7 (c ϭ 1.0, CHCl3). 1H NMR (300 MHz,
CDCl3): δ ϭ Ϫ0.04 (s, 3 H), 0.04 (s, 3 H), 0.71 (s, 9 H), 1.97 (s, 3
Experimental Section
General Remarks: Solvents were distilled from the appropriate dry-
ing agents before use. Unless otherwise stated, all reactions were
performed in oven-dried glassware under an argon atmosphere in
dry solvents and monitored by TLC on silica gel HF254 (0.5 mm,
Qingdao, China). Spots were viewed by UV light or by treatment
with 10% H2SO4 in methanol followed by heating. Flash chroma-
tography was performed with the indicated solvent system on silica
gel H (400 mesh, Qingdao, China). Optical rotations were meas-
ured with a PerkinϪElmer 241 MC polarimeter. NMR spectra H), 2.03 (s, 3 H), 2.05 (s, 3 H), 2.17 (s, 3 H), 3.38 (t, J ϭ 9.3 Hz, 1
were recorded with Bruker AM 300 or Inova 600 spectrometers in
CDCl3 as solvent and with tetramethylsilane as an internal refer-
H), 3.68 (t, J ϭ 10.1 Hz, 1 H), 3.70 (dd, J ϭ 9.1, 3.6 Hz, 1 H), 3.89
(m, 2 H), 4.04Ϫ4.20 (m, 5 H), 4.24 (dd, J ϭ 10.2, 4.9 Hz, 1 H),
ence. Mass spectra were recorded with HP5989A or VG Quattro 4.84 (d, J ϭ 7.9 Hz, 1 H), 4.93 (d, J ϭ 3.6 Hz, 1 H), 4.97 (dd, J ϭ
mass spectrometers. Elemental analyses were performed with a 10.4, 3.4 Hz, 1 H), 5.22 (m, 1 H), 5.24 (t, J ϭ 10.5 Hz, 1 H),
968
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Synthesis of Trisaccharide and Tetrasaccharide Moieties
FULL PAPER
5.35Ϫ5.42 (m, 2 H), 5.45 (s, 1 H), 5.95 (m, 1 H) ppm. 13C NMR
was dried with MgSO4 and concentrated in vacuo to give a residue
(75 MHz, CDCl3): δ ϭ 170.3, 170.2, 170.1, 169.2, 137.2, 134.1, that was purified by flash column chromatography (petroleum
129.1, 128.1, 126.5, 117.1, 102.4, 101.0, 98.8, 82.8, 78.7, 71.3, 71.2, ether/EtOAc, 3:1) to afford the title compound 13 (751 mg, 83%)
70.8, 69.4, 69.2, 68.9, 67.1, 62.2, 61.1, 26.0, 21.1, 20.6, 20.5, 18.2,
as a white foam: [α]2D8 ϭ ϩ99.8 (c ϭ 1.3, CHCl3). 1H NMR
Ϫ4.2, Ϫ4.3 ppm. ESI MS: m/z ϭ 776 [M ϩ Naϩ], 1529 [2M ϩ (300 MHz, CDCl3): δ ϭ 3.50 (t, J ϭ 9.8 Hz, 1 H), 3.71 (m, 2 H),
Naϩ]. C36H52O15Si (752.9): calcd. C 57.43, H 6.96; found C 57.02, 3.88 (m, 1 H), 3.99Ϫ4.37 (m, 5 H), 4.48 (dd, J ϭ 11.4, 5.9 Hz, 1
H 6.99.
H), 4.56 (dd, J ϭ 11.5, 7.1 Hz, 1 H), 5.05 (d, J ϭ 3.6 Hz, 1 H),
5.17Ϫ5.22 (d, J ϭ 7.9 Hz, 2 H), 5.32Ϫ5.39 (m, 1 H), 5.50 (s, 1 H),
5.60 (dd, J ϭ 10.5, 3.4 Hz, 1 H), 5.85 (dd, J ϭ 10.6, 7.9 Hz, 1 H),
5.94 (m, 1 H), 5.98 (d, J ϭ 3.0 Hz, 1 H), 7.20Ϫ8.10 (m, 25 H) ppm.
EI MS: m/z ϭ 579, 334, 105, 57. C50H46O15·H2O (904.9): calcd. C
66.37, H 5.35; found C 65.94, H 5.13.
Allyl 2,3,4,6-Tetra-O-benzoyl-β-
benzylidene-3-O-tert-butyldimethylsilyl-α-
A mixture of donor 10b (0.81 g, 1.26 mmol), acceptor 4 (0.44 g,
1.04 mmol) and powdered molecular sieves (4 A, 0.4 g) in CH2Cl2
D
-galactopyranosyl-(1Ǟ2)-4,6-O-
D-glucopyranoside (11b):
˚
(15 mL) was stirred at room temperature under Ar for 30 min and
then cooled to Ϫ15 °C. NIS (0.35 g, 1.56 mmol) was added to this
mixture, followed by addition of a solution of AgOTf (134 mg, pyranosyl)-3-O-(2,3,4-tri-O-acetyl-β-
0.52 mmol) in toluene (1.0 mL). The reaction mixture was allowed
Allyl 4,6-O-Benzylidene-2-O-(2,3,4,6-tetra-O-benzoyl-β-
-xylopyranosyl)-α-
pyranoside (14): Ethyl 2,3,4-tri-O-acetyl-1-thio-β--xylopyrano-
to warm to room temperature and stirred for 30 min, and then side[26] (22 mg, 68.7 µmol) and acceptor 13 (52 mg, 58.6 µmol) were
D
-galacto-
D
D
-gluco-
quenched with Et3N. The suspension was diluted with EtOAc and
filtered through a pad of Celite, and the filtrate was washed suc-
dissolved in CH2Cl2 (1.5 mL) containing activated powdered mo-
lecular sieves (4 A, 30 mg) under Ar. The mixture was stirred at
˚
cessively with 10% Na2S2O3 and water. The organic layer was dried room temperature for 30 min and then cooled to Ϫ20 °C. NIS
with MgSO4, and concentrated in vacuo to give a residue, which (19 mg, 84 µmol) was added, followed by a solution of AgOTf
was purified by flash column chromatography (petroleum ether/ (7 mg) in dry toluene (0.2 mL). The cooling bath was removed and
EtOAc, 6:1 Ǟ 5:1) to give 11b (1.01 g, 97%) as a white foam: the suspension was allowed to warm to room temperature with
[α]D21 ϭ ϩ83.2 (c ϭ 0.95, CHCl3). 1H NMR (300 MHz, CDCl3): δ ϭ
stirring for around 30 min, after which the reaction was quenched
3.29 (t, J ϭ 9.6 Hz, 1 H), 3.64 (t, J ϭ 10.2 Hz, 1 H), 3.78 (dd, J ϭ with Et3N and the mixture was filtered through Celite. The filtrate
9.1, 3.7 Hz, 1 H), 3.88 (m, 1 H), 4.07Ϫ4.33 (m, 5 H), 4.44 (dd, J ϭ was diluted with EtOAc, washed successively with 10% Na2S2O3
11.3, 6.0 Hz, 1 H), 4.64 (dd, J ϭ 11.3, 7.0 Hz, 1 H), 5.13 (d, J ϭ and cold water, and then dried with MgSO4 and concentrated in
3.7 Hz, 1 H), 5.18 (d, J ϭ 7.9 Hz, 1 H), 5.22Ϫ5.27 (m, 1 H), 5.41 vacuo. The residue was purified by flash column chromatography
(s, 1 H), 5.42Ϫ5.50 (m, 1 H), 5.57 (dd, J ϭ 10.4, 3.4 Hz, 1 H), 5.90 (petroleum ether/EtOAc, 3:1 Ǟ 2:1) to give the trisaccharide 14
(dd, J ϭ 10.4, 7.8 Hz, 1 H), 5.96 (d, J ϭ 2.5 Hz, 1 H), 6.04 (m, 1
(67 mg, quant.) as a white foam: [α]2D2 ϭ ϩ43.8 (c ϭ 1.0, CHCl3).
H), 7.15Ϫ8.10 (m, 25 H) ppm. 13C NMR (75 MHz,CDCl3): δ ϭ 1H NMR (300 MHz, CDCl3): δ ϭ 1.99 (s, 6 H), 2.11 (s, 3 H), 2.82
166.0, 165.6, 165.5, 165.4, 137.2, 134.1, 133.8, 133.6, 133.3, 133.2, (dd, J ϭ 12.1, 6.9 Hz, 1 H), 3.46 (t, J ϭ 9.5 Hz, 1 H), 3.67 (t, J ϭ
133.1, 130.3, 130.0, 129.9, 129.7, 129.6, 129.5, 129.1, 129.0, 128.6, 10.3 Hz, 1 H), 3.87 (m, 1 H), 3.91 (dd, J ϭ 9.5, 3.8 Hz, 1 H), 3.97
128.5, 128.2, 128.1, 127.8, 126.5, 117.2, 102.3, 101.4, 99.0, 82.8,
79.3, 72.1, 71.6, 71.0, 70.4, 69.2, 68.9, 68.3, 62.2, 62.0, 25.9, 18.1,
Ϫ4.2, Ϫ4.4 ppm. ESI MS: m/z ϭ 1023 [M ϩ Naϩ], 1047 [M ϩ 1
ϩ 2Naϩ]. C56H60O15Si·2H2O (1037.2): calcd. C 64.85, H 6.22;
found C 64.85, H 5.72.
(dd, J ϭ 12.4, 4.9 Hz, 1 H), 4.12 (m, 1 H), 4.19Ϫ4.34 (m, 4 H),
4.42 (dd, J ϭ 11.2, 6.3 Hz, 1 H), 4.63 (dd, J ϭ 11.0, 6.5 Hz, 1 H),
4.75 (m, 1 H), 4.85 (m, 3 H), 5.03 (d, J ϭ 3.8 Hz, 1 H), 5.10 (d,
J ϭ 7.9 Hz, 1 H), 5.21Ϫ5.26 (m, 1 H), 5.41Ϫ5.47 (m, 1 H), 5.46
(s, 1 H), 5.63 (dd, J ϭ 10.5, 3.5 Hz, 1 H), 5.85 (dd, J ϭ 10.5, 7.9 Hz,
1 H), 5.98 (d, J ϭ 2.8 Hz, 1 H), 5.90Ϫ6.02 (m, 1 H), 7.20Ϫ8.11
(m, 25 H) ppm. ESI MS: m/z ϭ 1168 [M ϩ 1 ϩ Naϩ], 1191 [M ϩ
1 ϩ 2Naϩ]. C61H60O22·H2O (1163.1): calcd. C 62.99, H 5.37; found
C 62.90, H 5.23.
Allyl 2,3,4,6-Tetra-O-benzoyl-β-D-galactopyranosyl-(1Ǟ2)-4,6-O-
benzylidene-3-O-para-methoxylbenzyl-α-
D-glucopyranoside (12):
The coupling of donor 10b (51 mg, 79.6 µmol) and acceptor 7
(30 mg, 70 µmol) was performed in the same way as described for
11b to give ortho ester 12 (77 mg, 100%) as a white foam: [α]2D1
ϩ79.0 (c ϭ 0.25, CHCl3). H NMR (300 MHz, CDCl3): δ ϭ 4.37, (2,3,4-tri-O-acetyl-β-
4.50 (AB peak, J ϭ 12.6 Hz, 2 H), 4.61 (dd, 1 H), 5.16 (d, J ϭ
ϭ
Allyl
2-O-(2,3,4,6-Tetra-O-benzoyl-β-
-xylopyranosyl)-α- -glucopyranoside (15): A
solution of trisaccharide 14 (145 mg, 0.13 mmol) in HOAc (80%,
3.6 Hz, 1 H), 5.20 (d, J ϭ 8.2 Hz, 1 H), 5.21Ϫ5.25 (m, 1 H), 4 mL) was stirred at 70 °C overnight, and then concentrated in
D-galactopyranosyl)-3-O-
1
D
D
5.40Ϫ5.47 (m, 1 H), 5.50 (s, 1 H), 5.60 (dd, J ϭ 10.4, 3.3 Hz, 1 H),
5.98 (m, 3 H), 6.68, 6.93 (AB peak, J ϭ 8.5 Hz, 2 H), 7.20Ϫ7.67
vacuo to give a residue, which was azeotroped three times with
toluene and purified by flash column chromatography (petroleum
(m, 17 H), 7.78Ϫ8.12 (4d, 8 H) ppm. 13C NMR (75 MHz, CDCl3): ether/EtOAc, 2:1) to afford the title compound 15 (103 mg, 77%)
δ ϭ 166.0, 165.6, 165.5, 165.1, 159.0, 137.4, 133.9, 133.6, 133.3,
133.1, 130.6, 130.0, 129.8, 129.7, 129.4, 129.0, 128.9, 128.6, 128.5,
as a white foam: [α]1D8 ϭ ϩ62.9 (c ϭ 1.0, CHCl3). 1H NMR
(300 MHz, CDCl3): δ ϭ 2.00 (s, 3 H), 2.01 (s, 3 H), 2.26 (s, 3 H),
128.4, 128.3, 128.1, 126.1, 117.34, 117.25, 114.0, 113.5, 102.4, 2.60 (t, J ϭ 10.2 Hz, 1 H), 3.40 (t, J ϭ 8.9 Hz, 1 H), 3.67Ϫ3.74
101.4, 98.7, 82.2, 80.4, 74.5, 72.0, 71.4, 70.0, 69.1, 68.9, 68.2, 62.4, (m, 3 H), 3.79Ϫ3.96 (m, 3 H), 4.14 (m, 1 H), 4.20Ϫ4.31 (m, 3 H),
62.1, 55.2 ppm. ESI MS: m/z ϭ 1029 [M ϩ Naϩ], 1052 [M ϩ
4.41 (dd, J ϭ 11.4, 6.3 Hz, 1 H), 4.63 (dd, J ϭ 11.4, 7.0 Hz, 1 H),
2Naϩ]. C58H54O16·0.5H2O (1016.1): calcd. C 68.56, H 5.46; found 4.77 (t, J ϭ 8.9 Hz, 1 H), 4.82 (m, 1 H), 4.88 (d, J ϭ 8.0 Hz, 1 H),
C 68.23, H 5.38.
4.92 (d, J ϭ 7.8 Hz, 1 H), 5.02 (d, J ϭ 3.6 Hz, 1 H), 5.26Ϫ5.31 (m,
1 H), 5.50Ϫ5.57 (m, 1 H), 5.56 (dd, J ϭ 10.5, 3.4 Hz, 1 H), 5.90
(dd, J ϭ 10.6, 7.9 Hz, 1 H), 5.96 (d, J ϭ 2.8 Hz, 1 H), 5.96Ϫ6.07
(m, 1 H), 7.20Ϫ8.11 (m, 20 H) ppm. ESI MS: m/z ϭ 1079 [M ϩ
Naϩ], 1102 [M ϩ 2Naϩ]. C54H56O22·H2O (1075.0): calcd. C 60.02,
H 5.19; found C 60.33, H 5.44.
Allyl 2,3,4,6-Tetra-O-benzoyl-β-D-galactopyranosyl-(1Ǟ2)-4,6-O-
benzylidene-α-D-glucopyranoside (13): Disaccharide 11b (1.02 g,
1.02 mmol) was dissolved in dry Py (4 mL) and cooled to 0 °C
under Ar. HF in Py (70%, 2 mL) was added dropwise. The mixture
was stirred at room temperature overnight, and then neutralized
with aqueous NaHCO3, diluted with EtOAc and washed success-
ively with saturated aqueous NaHCO3 and brine. The organic layer β-
Allyl 4-O-Acetyl-6-O-triphenylmethyl-2-O-(2,3,4,6-tetra-O-benzoyl-
D
-galactopyranosyl)-3-O-(2,3,4-tri-O-acetyl-β-D-xylopyranosyl)-α-
Eur. J. Org. Chem. 2004, 965Ϫ973
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 969

X. Zhu, B. Yu, Y. Hui, R. R. Schmidt
FULL PAPER
D
-glucopyranoside (16): TrCl (79 mg, 0.28 mmol) was added under
silica gel containing EtOAc. The precipitated solid was filtered and
washed with EtOAc, and the filtrate was concentrated in vacuo.
Ar to a stirred solution of the sugar diol 15 (188 mg, 0.18 mmol)
in dry Py (1.6 mL). The mixture was stirred at 80 °C for 2 h, and Silica gel chromatography (petroleum ether/EtOAc, 2:1) yielded the
then concentrated under reduced pressure. The residue was purified
by flash column chromatography (petroleum ether/EtOAc, 4:1) to
title compound 18 (48 mg, 90%) as a white foam: [α]2D6 ϭ ϩ59.3
(c ϭ 1.4, CHCl3). 1H NMR (300 MHz, CDCl3): δ ϭ 1.45 (s, 9 H),
give a white foam, the tritylated intermediate (213 mg, 92%): 2.00 (s, 9 H), 2.14 (s, 3 H), 2.52 (m, 1 H), 3.77 (m, 1 H), 3.91 (dd,
[α]2D1 ϭ ϩ59.3 (c ϭ 1.0, CHCl3). 1H NMR (300 MHz, CDCl3): δ ϭ
J ϭ 10.9, 3.4 Hz, 1 H), 4.14Ϫ4.33 (m, 5 H), 4.46 (m, 2 H), 4.55
2.02 (s, 3 H), 2.04 (s, 3 H), 2.26 (s, 3 H), 2.60 (t, J ϭ 9.6 Hz, 1 H), (dd, J ϭ 11.2, 6.7 Hz, 1 H), 4.67Ϫ4.76 (m, 3 H), 4.98Ϫ5.08 (m, 2
3.14 (br. s, 1 H), 3.25Ϫ3.49 (m, 3 H), 3.80Ϫ3.98 (m, 4 H), H), 5.17 (d, J ϭ 3.6 Hz, 1 H), 5.28Ϫ5.32 (m, 1 H), 5.50Ϫ5.56 (m,
4.22Ϫ4.37 (m, 4 H), 4.50 (dd, J ϭ 11.0, 6.4 Hz, 1 H), 4.64 (dd, J ϭ
1 H), 5.59 (dd, J ϭ 10.7, 3.3 Hz, 1 H), 5.90 (dd, J ϭ 10.7, 7.8 Hz,
11.0, 6.4 Hz, 1 H), 4.77Ϫ4.85 (m, 2 H), 4.91 (d, J ϭ 8.0 Hz, 1 H), 1 H), 5.98 (d, J ϭ 3.2 Hz, 1 H), 5.97Ϫ6.09 (m, 1 H), 7.20Ϫ8.10
5.00 (d, J ϭ 8.0 Hz, 1 H), 5.15 (d, J ϭ 3.8 Hz, 1 H), 5.31Ϫ5.35 (m,
(m, 20 H) ppm. ESI MS: m/z ϭ 1191 [M ϩ Naϩ], 1214 [M ϩ
1 H), 5.60 (m, 2 H), 5.96 (dd, J ϭ 10.7, 7.9 Hz, 1 H), 6.01 (d, J ϭ 2Naϩ]. C60H64O24 (1169.1): calcd. C 61.64, H 5.52; found C 61.28,
3.3 Hz, 1 H), 6.10 (m, 1 H), 7.20Ϫ8.12 (m, 35 H) ppm. ESI MS: H 5.57.
m/z ϭ 1322 [M ϩ 1 ϩ Naϩ], 1344 [M ϩ 2Naϩ]. C73H70O22·H2O
(1317.4): calcd. C 66.56, H 5.51; found C 66.89, H 5.43.
tert-Butyl
pyranosyl)-3-O-(2,3,4-tri-O-acetyl-β-
pyranose]uronate (19): [Pd(PPh3)4] (13 mg, 11.2 µmol) and HOAc
[4-O-Acetyl-2-O-(2,3,4,6-tetra-O-benzoyl-β-
D-galacto-
D
-xylopyranosyl)-α-
D
-gluco-
Ac2O (0.05 mL) was added to a solution of the above tritylated
trisaccharide (88 mg, 67.7 µmol) in Py (2 mL), and the reaction (0.6 mL) were added to allyl glycoside 18 (40 mg, 34 µmol) under
mixture was stirred at room temperature overnight. The mixture
was then concentrated to give a residue, which was purified by flash
Ar. The mixture was protected from light and stirred at 80 °C for
1 h, and then filtered through a short silica gel column. The solvent
column chromatography (petroleum ether/EtOAc, 4:1) to give the was removed under vacuum to give the crude product, which was
title compound 16 (93 mg, quant.) as a white foam: [α]2D4 ϭ ϩ61.1
(c ϭ 1.3, CHCl3). 1H NMR (300 MHz, CDCl3): δ ϭ 1.73 (s, 3 H),
purified by flash column chromatography (petroleum ether/EtOAc,
2:1) to afford the hemiacetal 19 (38 mg, 98%) as a white foam:
1
1.99 (s, 3 H), 2.05 (s, 3 H), 2.13 (s, 3 H), 3.10 (m, 2 H), 3.72 (m, 1 [α]D26 ϭ ϩ61.9 (c ϭ 0.9, CHCl3). H NMR (300 MHz, CDCl3): δ ϭ
H), 3.85 (dd, J ϭ 11.0, 3.6 Hz, 1 H), 3.94 (m, 1 H), 4.08Ϫ4.16 (m, 1.42 (s, 9 H), 2.00 (s, 3 H), 2.01 (s, 3 H), 2.03 (s, 3 H), 2.05 (s, 3
2 H), 4.21Ϫ4.38 (m, 3 H), 4.44Ϫ4.50 (m, 2 H), 4.58Ϫ4.79 (m, 5
H), 2.61 (m, 1 H), 3.76Ϫ3.93 (m, 2 H), 4.07Ϫ4.19 (m, 2 H), 4.29
H), 5.01 (d, J ϭ 7.9 Hz, 1 H), 5.14 (d, J ϭ 3.8 Hz, 1 H), 5.28Ϫ5.38 (m, 1 H), 4.39Ϫ4.62 (m, 3 H), 4.73 (m, 3 H), 5.02 (m, 2 H), 5.48
(m, 1 H), 5.52Ϫ5.62 (m, 2 H), 5.92 (dd, J ϭ 10.7, 7.9 Hz, 1 H), (d, J ϭ 8.9 Hz, 1 H), 5.65 (dd, J ϭ 10.6, 3.4 Hz, 1 H), 5.85 (dd,
5.98 (d, J ϭ 3.5 Hz, 1 H), 6.01Ϫ6.16 (m, 1 H), 7.20Ϫ8.11 (m, 35
J ϭ 10.6, 7.8 Hz, 1 H), 5.98 (d, J ϭ 3.2 Hz, 1 H), 7.16Ϫ8.10 (m,
H) ppm. ESI MS: m/z ϭ 1364 [M ϩ 1 ϩ Naϩ], 1387 [M ϩ 1 ϩ 20 H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 170.0, 169.7, 169.1,
2Naϩ]. C75H72O23·H2O (1359.4): calcd. C 66.27, H 5.49; found C
66.42, H 5.41.
167.0, 166.2, 165.5, 165.3, 133.7, 133.6, 133.4, 129.9, 129.8, 129.7,
129.2, 128.9, 128.7, 128.6, 128.3, 101.7, 99.2, 92.1, 82.5, 79.1, 74.6,
72.2, 71.7, 71.0, 70.1, 69.6, 69.1, 68.7, 68.2, 62.0, 61.3, 29.7, 27.8,
20.9, 20.7 ppm. ESI MS: m/z ϭ 1151 [M ϩ Naϩ], 1174 [M ϩ
2Naϩ]. C57H60O24 (1129.1): calcd. C 60.64, H 5.36; found C 60.75,
H 5.70.
Allyl
4-O-Acetyl-2-O-(2,3,4,6-tetra-O-benzoyl-β-
D-galactopyr-
anosyl)-3-O-(2,3,4-tri-O-acetyl-β-
D-xylopyranosyl)-α-D-glucopyrano-
side (17): Compound 16 (358 mg, 0.27 mmol) was treated with
HOAc (80%, 5 mL) at 50 °C for 4 h, and the solvent was then
removed under reduced pressure to give the crude product, which
was purified by flash column chromatography (petroleum ether/
tert-Butyl
[4-O-Acetyl-2-O-(2,3,4,6-tetra-O-benzoyl-β-
D-galacto-
pyranosyl)-3-O-(2,3,4-tri-O-acetyl-β-
D-xylopyranosyl)-α-D-glucopyr-
EtOAc, 1:1) to afford the title compound 17 (179 mg, 61%) as a anosyl Trichloroacetimidate]uronate (20): CCl3CN (20 µL,
white foam: [α]2D8 ϭ ϩ69.2 (c ϭ 1.1, CHCl3). H NMR (600 MHz,
0.2 mmol) and catalytic DBU were added to a solution of 19
1
CDCl3): δ ϭ 2.00 (s, 6 H), 2.03 (s, 3 H), 2.14 (s, 3 H), 2.55 (m, 1 (33 mg, 29.2 µmol) in CH2Cl2 (2 mL). After stirring at room tem-
H), 3.52 (dd, J ϭ 12.4, 4.0 Hz, 1 H), 3.64 (d, J ϭ 12.4 Hz, 1 H), perature for 30 min, the reaction mixture was concentrated in va-
3.74Ϫ3.80 (m, 2 H), 3.83 (dd, J ϭ 9.4, 3.0 Hz, 1 H), 4.10Ϫ4.17 (m, cuo and the residue was purified by flash column chromatography
1 H), 4.21Ϫ4.29 (m, 3 H), 4.43 (dd, J ϭ 11.2, 6.0 Hz, 1 H), 4.52
(d, J ϭ 5.6 Hz, 1 H), 4.61 (dd, J ϭ 11.3, 8.9 Hz, 1 H), 4.72 (m, 3
H), 4.81 (t, J ϭ 9.6 Hz, 1 H), 5.01 (d, J ϭ 7.8 Hz, 1 H), 5.10 (d,
(petroleum ether/EtOAc, 2:1 ϩ1% Et3N) to furnish the title com-
pound 20 (32 mg, 86%) as a white foam. 1H NMR (300 MHz,
CDCl3): δ ϭ 1.42 (s, 9 H), 2.00 (s, 3 H), 2.01 (s, 6 H), 2.14 (s, 3
J ϭ 2.9 Hz, 1 H), 5.28, 5.51 (m, 2 H), 5.61 (dd, J ϭ 10.5, 3.1 Hz, H), 2.59 (m, 1 H), 3.80 (dd, J ϭ 10.9, 3.4 Hz, 1 H), 4.10 (dd, J ϭ
1 H), 5.91 (dd, J ϭ 10.5, 7.9 Hz, 1 H), 5.98 (d, J ϭ 2.7 Hz, 1 H),
6.02 (m, 1 H), 7.20Ϫ8.09 (m, 20 H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 170.6, 170.0, 169.7, 169.2, 166.0, 165.4, 165.2, 133.7,
133.44, 133.35, 129.9, 129.8, 129.7, 129.2, 129.0, 128.9, 128.7,
11.2, 6.6 Hz, 1 H), 4.19 (t, J ϭ 9.2 Hz, 1 H), 4.25Ϫ4.31 (m, 2 H),
4.40Ϫ4.48 (m, 2 H), 4.57Ϫ4.76 (m, 4 H), 5.02 (d, J ϭ 7.8 Hz, 1
H), 5.13 (t, 1 H), 5.56 (dd, J ϭ 10.7, 3.3 Hz, 1 H), 5.80 (dd, J ϭ
10.7, 7.8 Hz, 1 H), 5.96 (d, J ϭ 3.2 Hz, 1 H), 6.74 (d, J ϭ 3.6 Hz,
128.5, 128.3, 117.3, 101.3, 99.1, 97.8, 78.7, 74.6, 72.2, 71.9, 71.8, 1 H), 7.18Ϫ8.05 (m, 20 H), 8.74 (s, 1 H) ppm. ESIMS: m/z ϭ 1296
71.3, 70.1, 69.3, 69.1, 68.8, 68.2, 61.9, 61.4, 61.3, 21.2, 20.9,
20.7 ppm. ESI MS: m/z ϭ 1122 [M ϩ 1 ϩ Naϩ], 1145 [M ϩ 1 ϩ
2Naϩ]. C56H58O23·H2O (1117.1): calcd. C 60.21, H 5.41; found C
60.32, H 5.23.
[M ϩ Naϩ], 1319 [M ϩ2Naϩ].
3Ј-O-Acetyl-2,3-O-isopropylidene-α/β-D-apiofuranose (22): Com-
pound 21[29] (2.47 g, 13 mmol) was dissolved in dry Py (40 mL),
and Ac2O (2.85 mL) was added to this mixture at 0 °C. The re-
sulting mixture was stirred at room temperature overnight, and was
then diluted with EtOAc, washed successively with 5% HCl, satu-
rated aqueous NaHCO3 and brine, dried with MgSO4 and concen-
trated. The residue was dissolved in NH3-THF/MeOH (100 mL)
tert-Butyl
[Allyl
4-O-Acetyl-2-O-(2,3,4,6-tetra-O-benzoyl-β-
D
-
-
galactopyranosyl)-3-O-(2,3,4-tri-O-acetyl-β-
D
-xylopyranosyl)-α-
D
glucopyranoside]uronate (18): PDC (35 mg, 91 µmol), Ac2O (43 µL)
and tBuOH (85 µL) were added to a stirred solution of sugar al-
cohol 17 (50 mg, 45.5 µmol) in CH2Cl2 (0.6 mL). The mixture was and stirred at 0 °C until all the starting material was consumed
stirred at room temperature for 6 h, and then poured into a pad of (TLC). The solvent was then evaporated and the residue was puri-
970
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 965Ϫ973

Synthesis of Trisaccharide and Tetrasaccharide Moieties
FULL PAPER
fied by flash column chromatography (petroleum ether/EtOAc, 3:1)
thio-α-
L-rhamnoside (26): A suspension of imidate 25 (127 mg,
to give a colourless syrup, the title compound 22 (1.2 g, 40%) as
0.18 mmol), ethyl 2,3-O-isopropylidene-1-thio-α--rhamnoside
an α/β mixture. 1H NMR (300 MHz, CDCl3): δ ϭ 1.40 (s, 3 H), (47 mg, 0.19 mmol) and activated powdered molecular sieves (4 A,
˚
1.48 (s, 3 H), 2.10 (s, 3 H), 4.00 (AB peak, J ϭ 12.3 Hz, 2 H, H-
4), 4.24 and 4.41 (AB peak, J ϭ 11.7 Hz, 2 H, H-3), 4.38 (s, 1 H,
100 mg) in CH2Cl2 (3 mL) was stirred at room temperature for
15 min and then cooled to Ϫ50 °C, and a solution of TMSOTf
H-2α), 5.05 (d, J ϭ 2.8 Hz, 1 H, H-1β), 5.42 (s, 1 H, H-1α) ppm. (0.72 mL, 0.05 ) in CH2Cl2 was slowly added to the reaction mix-
EI MS: m/z ϭ 217, 173, 157, 43.
ture. After stirring for 30 min, the reaction mixture was quenched
with Et3N, and filtered. The filtrates were concentrated in vacuo to
give a residue, which was purified by flash column chromatography
(petroleum ether/EtOAc, 6:1) to yield the title compound 26
(135 mg, 95%) as a white foam: [α]1D9 ϭ Ϫ102.5 (c ϭ 0.9, CHCl3).
1H NMR (600 MHz, CDCl3): δ ϭ 1.27 (m, 12 H), 1.33 (s, 3 H),
1.52 (s, 3 H), 1.99 (s, 3 H), 2.62Ϫ2.50 (m, 2 H), 3.56 (dd, J ϭ 12.0,
7.0 Hz, 1 H), 3.60 (dd, J ϭ 10.0, 7.5 Hz, 1 H), 3.72 and 3.77 (AB
peak, J ϭ 10.2 Hz, 2 H), 3.94 (m, 1 H), 4.00 (t, J ϭ 5.8 Hz, 1 H),
4.05 (d, J ϭ 6.0 Hz, 1 H), 4.22Ϫ4.26 (m, 2 H), 4.03 and 4.18 (AB
peak, J ϭ 11.7 Hz, 2 H), 4.28 (s, 1 H), 5.11 (td, J ϭ 7.1, 4.5 Hz, 1
H), 5.21 (m, 2 H), 5.25 (s, 1 H), 5.47 (s, 1 H), 7.41Ϫ8.06 (m, 10 H)
ppm. EI MS: m/z ϭ 788, 555, 323, 105. C40H50O15S (802.9): calcd.
C 59.88, H 6.28; found C 60.15, H 6.22.
3Ј-O-Acetyl-2,3-O-isopropylidene-α/β-D-apiofuranosyl Trichloroace-
timidate (23): A solution of hemiacetal 22 (253 mg, 1.1 mmol),
CCl3CN (0.6 mL, 6 mmol) and catalytic DBU in CH2Cl2 (7 mL)
was stirred at room temperature for 20 min, after which the solvent
was removed under reduced pressure, and the resulting residue was
purified by flash column chromatography (petroleum ether/EtOAc,
7:1 ϩ 1% Et3N) to give the title compound 23 (402 mg, 98%) as a
colourless syrup. Imidate 23 was found to decompose in the NMR
tube and was therefore immediately used in the next step without
further identification.
Benzyl 3-O-(3Ј-O-Acetyl-2,3-O-isopropylidene-β-
D-apiofuranosyl)-
2,4-di-O-benzoyl-α- -xylopyranoside (24): A suspension of imidate
D
23 (244 mg, 0.65 mmol), benzyl 2,4-di-O-benzoyl-α--xylopyrano-
Ethyl 3Ј-O-Acetyl-2,3-O-isopropylidene-β-
2,4-di-O-benzoyl-β- -xylopyranosyl-(1Ǟ4)-2,3-di-O-acetyl-1-thio-α-
-rhamnoside (28): A typical set of conditions for the removal of
D-apiofuranosyl-(1Ǟ3)-
side (333 mg, 0.74 mmol) and activated powdered molecular sieves
D
˚
(4 A, 700 mg) in CH2Cl2 (5 mL) was stirred at room temperature
L
for 15 min. It was then cooled to Ϫ15 °C, and a solution of
TMSOTf (5 mL, 0.05 ) in CH2Cl2 was slowly added to the reac-
tion mixture. After stirring for another 30 min, the reaction mixture
was quenched with Et3N and filtered. The filtrates were concen-
trated in vacuo to give a residue, which was purified by flash col-
umn chromatography (petroleum ether/EtOAc, 6:1 Ǟ 4:1) to afford
the disaccharide 24 (386 mg, 90%) as a white foam. A small amount
of α-isomer produced in this step could be removed completely
after next reaction. 24: 1H NMR (300 MHz, CDCl3): δ ϭ 3.64 (AB
peak, J ϭ 12.3 Hz, 2 H), 3.79Ϫ3.90 (m, 2 H), 3.91 and 4.06 (AB
peak, J ϭ 11.8 Hz, 2 H), 4.22 (s, 1 H), 4.58 (t, J ϭ 9.6 Hz, 1 H),
4.50 and 4.75 (AB peak, J ϭ 12.6 Hz, 2 H), 5.17Ϫ5.25 (m, 2 H),
5.36 (s, 1 H), 7.10Ϫ8.10 (m, 15 H) ppm. EI MS: m/z ϭ 648, 556,
368, 341, 215, 105. C36H38O12·H2O (680.7): calcd. C 63.52, H 5.92;
found C 63.21, H 5.62.
isopropylidene from 26 is described as follows: a solution of 26
(140 mg, 0.17 mmol) in 90% HOAc (3 mL) was stirred at 90 °C
overnight and then concentrated in vacuo, and the traces of HOAc
and water were removed by coevaporation several times with tolu-
ene. The crude product 27 was dissolved in Py (2.5 mL) and Ac2O
(0.6 mL) and stirred overnight at room temperature, and was then
diluted with EtOAc, washed successively with 5% HCl, saturated
aqueous NaHCO3 and brine, dried with MgSO4 and concentrated
in vacuo. The residue was purified by flash column chromatogra-
phy (petroleum ether/EtOAc, 4:1 Ǟ 3:1) to afford the title com-
pound 28 (108 mg, 73%) as a white solid: [α]2D8 ϭ Ϫ147.4 (c ϭ 1.3,
1
CHCl3). H NMR (300 MHz, CDCl3): δ ϭ 1.26 (t, J ϭ 7.4 Hz, 3
H), 1.26 (s, 3 H), 1.33 (s, 3 H), 1.36 (d, J ϭ 6.3 Hz, 3 H), 1.86 (s,
3 H), 1.99 (s, 3 H), 2.10 (s, 3 H), 2.59 (m, 2 H), 3.62 (dd, J ϭ 12.1,
6.6 Hz, 1 H), 3.75 (AB peak, J ϭ 10.2 Hz, 2 H), 3.79 (t, J ϭ 5.9 Hz,
1 H), 4.20 (m, 3 H), 4.02 and 4.19 (AB peak, J ϭ 11.8 Hz, 2 H),
4.26 (s, 1 H), 4.94 (d, J ϭ 5.5 Hz, 1 H), 5.07 (dd, J ϭ 9.9, 3.3 Hz,
1 H), 5.11 (s, 1 H), 5.14 (m, 2 H), 5.24 (s, 1 H), 5.27 (dd, J ϭ 3.3,
1.5 Hz, 1 H), 7.40Ϫ8.04 (m, 10 H) ppm. EI MS: m/z ϭ 556, 341,
275, 215, 105. C41H50O17S (846.9): calcd. C 58.15, H 5.95; found
C 57.72, H 5.89.
3-O-(3Ј-O-Acetyl-2,3-O-isopropylidene-β-D-apiofuranosyl)-2,4-di-O-
benzoyl-α- -xylopyranosyl Trichloroacetimidate (25): A suspension
D
of 24 (428 mg, 0.65 mmol) and Pd/C (10%, 114 mg) in EtOAc/95%
EtOH (1:1, 20 mL) was stirred at room temperature under H2 at-
mosphere (1 atm) for 6 h and then filtered. The filtrates were con-
centrated in vacuo. Flash column chromatography of the residue
(petroleum ether/EtOAc, 2.5:1) gave the desired hemiacetal
(372 mg, quant.) as a colourless syrup, which was directly used in
the next reaction. Catalytic DBU (one drop) was added to a solu-
tion of the above hemiacetal (141 mg, 0.25 mmol) and CCl3CN
(0.14 mL, 1.4 mmol) in CH2Cl2 (3 mL), and the resulting mixture
was stirred at room temperature for 1 h and then concentrated in
vacuo. The residue was purified by flash column chromatography
(petroleum ether/EtOAc, 3:1 ϩ 1% Et3N) to furnish the title com-
pound 25 (158 mg, 89%) as a white foam: [α]2D0 ϭ Ϫ21.7 (c ϭ 1.2,
Ethyl 2,3-O-Isopropylidene-β-D-apiofuranosyl-(1Ǟ3)-β-D-xylopyr-
anosyl-(1Ǟ4)-2,3-O-isopropylidene-1-thio-α-
L-rhamnoside (29):
A
solution of NaOMe (0.23 mL, 0.1 ) in MeOH was added to a
solution of protected sugar 26 (188 mg, 0.23 mmol) in dry MeOH
(3 mL). The reaction mixture was stirred at room temperature over-
night. Amberlite IRC-85 resin was added until a pH of approxi-
mately 5 was obtained. The mixture was then filtered and concen-
trated to give the crude product 29 (87 mg, 68%) as a white solid,
which was directly used in the next step without purification.
1
CHCl3). H NMR (300 MHz, CDCl3) δ ϭ 1.22 (s, 3 H), 1.34 (s, 3
Ethyl 3Ј-O-Acetyl-2,3-O-isopropylidene-β-
D-apiofuranosyl-(1Ǟ3)-
H), 1.91 (s, 3 H), 3.67 (AB peak, J ϭ 10.2 Hz, 2 H), 3.85Ϫ4.14 (m,
4 H), 4.24 (s, 1 H), 4.59 (t, J ϭ 9.5 Hz, 1 H), 5.33 (m, 2 H), 5.34
(s, 1 H), 6.61 (d, J ϭ 3.8 Hz, 1 H), 7.40Ϫ8.08 (m, 10 H), 8.59 (s, 1
H) ppm. EI MS: m/z ϭ 702, 556, 215, 105. C31H32O12NCl3·0.5H2O
(726.0): calcd. C 51.29, H 4.58, N 1.93; found C 51.07, H 4.28,
N 2.31.
2,4-di-O-acetyl-β- -xylopyranosyl-(1Ǟ4)-2,3-di-O-acetyl-1-thio-α-L-
D
rhamnoside (30): A solution of 29 (53 mg, 96 µmol) in MeOH/H2O
(3:2, 5 mL) was treated at 70 °C overnight with Dowex 50 W (Hϩ)
resin (500 mg). The resin was removed and washed with MeOH,
and the solution was evaporated under vacuum to give a residue,
which was then dissolved in Ac2O (0.5 mL) and Py (2 mL) and
stirred overnight at room temperature. After having been quenched
with MeOH, the mixture was diluted with EtOAc, washed success-
Ethyl 3Ј-O-Acetyl-2,3-O-isopropylidene-β-D-apiofuranosyl-(1Ǟ3)-
2,4-di-O-benzoyl-β- -xylopyranosyl-(1Ǟ4)-2,3-O-isopropylidene-1-
D
Eur. J. Org. Chem. 2004, 965Ϫ973
www.eurjoc.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
971

X. Zhu, B. Yu, Y. Hui, R. R. Schmidt
FULL PAPER
ively with 5% HCl, saturated aqueous NaHCO3 and brine, dried
with MgSO4 and concentrated in vacuo. The residue was purified
by flash column chromatography (petroleum ether/EtOAc, 3:1) to
furnish the title compound 30 (54 mg, 78%) as a white foam. 1H
the traces of HOAc and water were removed by coevaporation sev-
eral times with toluene. The residue was dissolved in Py (10 mL)
and Ac2O (0.4 mL) and stirred overnight at room temperature, and
was then diluted with EtOAc, washed successively with 5% HCl,
NMR (300 MHz, CDCl3): δ ϭ 1.36, 1.44 (2s, 6 H, Me2C), 1.86 (s, saturated aqueous NaHCO3 and brine, dried with MgSO4 and con-
3 H, Ac), 1.92 (s, 3 H, Ac), 1.97 (s, 3 H, Ac), 1.99 (s, 3 H, Ac), centrated in vacuo. The residue was purified by flash column chro-
2.10 (s, 3 H, Ac), 2.60 (m, 2 H, SCH2CH3), 3.26 (dd, J5,5Ј ϭ 11.8, matography (petroleum ether/EtOAc, 4:1 Ǟ 3:1) to afford the title
J5,4 ϭ 9.2 Hz, 1 H, xyl-5), 3.65 (t, J3,2 ϭ J3,4 ϭ 9.6 Hz, 1 H, xyl-
compound 34 (108 mg, 73%) as a white foam: [α]2D1 ϭ Ϫ130.0 (c ϭ
3), 3.73 (t, J4,3 ϭ J4,5 ϭ 9.2 Hz, 1 H, rha-4), 3.79 and 3.92 (AB 1.0, CHCl3). 1H NMR (600 MHz, CDCl3): δ ϭ 1.27 (t, J ϭ 7.2 Hz,
peak, Jgem ϭ 10.0 Hz, 2 H, api-4), 4.07 (m, 2 H, xyl-5Ј, rha-5), 4.26
(s, 1 H, api-2), 4.13 and 4.30 (AB peak, Jgem ϭ 11.8 Hz, 2 H, api-
3 H), 1.38 (d, J ϭ 6.6 Hz, 3 H), 1.82 (s, 3 H), 1.91 (s, 3 H), 1.93
(s, 3 H), 2.01 (s, 3 H), 2.11 (s, 3 H), 2.61 (m, 2 H), 3.67 (dd, J ϭ
3), 4.55 (d, J1,2 ϭ 7.6 Hz, 1 H, xyl-1), 4.86 (m, 2 H, xyl-2, xyl-4), 12.3, 6.0 Hz, 1 H), 3.78 (t, J ϭ 9.6 Hz, 1 H), 3.99 and 4.06 (AB
5.05 (s, 1 H, api-1), 5.13 (s, 1 H, rha-1), 5.16 (dd, J3,2 ϭ 3.4, J3,4
9.7 Hz, 1 H, rha-3), 5.24 (dd, J2,3 ϭ 3.4, J2,1 ϭ 1.5 Hz, 1 H, rha-
2) ppm.
ϭ
peak, J ϭ 10.8 Hz, 2 H), 4.18 (m, 2 H), 4.33 (dd, J ϭ 12.3, 3.6 Hz,
1 H), 4.36 and 4.68 (AB peak, J ϭ 12.3 Hz, 2 H), 4.97 (d, J ϭ
4.8 Hz, 1 H), 5.10 (dd, J ϭ 7.2, 3.6 Hz, 1 H), 5.12 (d, J ϭ 1.2 Hz,
1 H), 5.17Ϫ5.26 (m, 2 H), 5.19 (s, 1 H), 5.26 (s, 1 H), 5.29 (dd, J ϭ
3.3, 1.5 Hz, 1 H), 7.33Ϫ8.07 (m, 10 H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 170.4, 169.9, 169.6, 169.2, 168.6, 165.5, 164.7, 133.4,
129.8, 129.7, 129.5, 129.2, 128.4, 128.3, 106.0, 100.0, 83.6, 81.7,
76.4, 75.2, 72.5, 72.3, 71.7, 71.1, 69.5, 67.5, 62.4, 61.1, 25.3, 21.0,
20.9, 20.8, 20.6, 20.1, 17.9, 14.7 ppm. ESI MS: m/z ϭ 913 [M ϩ
Naϩ], 936 (M ϩ2Naϩ). C42H50O19S·0.5H2O (899.9): calcd. C
55.96, H 5.71; found C 56.05, H 5.60.
2,4-Di-O-benzoyl-3-O-(2,3,3Ј-tri-O-acetyl-β-D-apiofuranosyl)-α-D-
xylopyranosyl trichloroacetimidate (32): A suspension of disacchar-
ide 31[35] (1.64 g, 2.32 mmol) and Pd/C (10%, 1.2 g) in EtOAc/95%
EtOH (1:2, 30 mL) was stirred at 40 °C under H2 atmosphere (50
atm) for 1 days and then filtered. The filtrates were concentrated in
vacuo. The residue was purified by flash column chromatography
(petroleum ether/EtOAc, 5:1 Ǟ 3:1) to afford the desired hemiace-
tal (532 mg, 37%) as a colourless syrup, together with recovered
starting material 31 (983 mg, 60%). Catalytic DBU (one drop) was
added to a solution of the above hemiacetal (450 mg, 0.73 mmol)
and CCl3CN (0.4 mL, 4 mmol) in CH2Cl2 (5 mL), and the resulting
solution was stirred at room temperature for 30 min and then con-
centrated in vacuo. The residue was purified by flash column chro-
matography (petroleum ether/EtOAc, 3:1 ϩ 1% Et3N) to afford the
imidate 32 (495 mg, 89%) as a white foam. 1H NMR (300 MHz,
CDCl3): δ ϭ 1.61 (s, 3 H), 1.88 (s, 3 H), 1.89 (s, 3 H), 3.92 (m, 3
H), 4.13 (dd, J ϭ 11.1, 5.9 Hz, 1 H), 4.28 and 4.47 (AB peak, J ϭ
12.6 Hz, 2 H), 4.51 (t, J ϭ 9.6 Hz, 1 H), 5.17 (s, 1 H), 5.24 (s, 1
H), 5.33Ϫ5.43 (m, 2 H), 6.59 (d, J ϭ 3.6 Hz, 1 H), 7.51Ϫ8.05 (m,
10 H), 8.61 (s, 1 H) ppm. EI MS: m/z ϭ 599, 340, 259, 105.
Allyl 2,3,3Ј-Tri-O-acetyl-β-
β- -xylopyranosyl-(1Ǟ4)-2,3-di-O-acetyl-α-
O-isopropylidene-α- -fucopyranoside (35): A mixture of trisacchar-
D-apiofuranosyl-(1Ǟ3)-2,4-di-O-benzoyl-
D
L-rhamnosyl-(1Ǟ2)-3,4-
D
ide 34 (22 mg, 24.7 µmol), allyl 3,4-O-isopropylidene-α--fucopyr-
anoside (7 mg, 28.7 µmol) and 4Ε powdered molecular sieves
(20 mg) in CH2Cl2 (5 mL) was stirred at room temperature under
Ar for 30 min and then cooled to Ϫ20 °C. NIS (8 mg, 36 µmol)
was added to this mixture, followed by addition of a solution of
AgOTf (3 mg, 11.7 µmol) in toluene (0.5 mL). After stirring for
1 h, the reaction mixture was quenched with Et3N. The suspension
was diluted with EtOAc and filtered through a pad of Celite, and
the filtrate was washed successively with 10% Na2S2O3 and water.
The organic layer was dried with MgSO4 and concentrated in va-
cuo to give a residue, which was purified by flash column chroma-
tography (petroleum ether/EtOAc, 2.5:1Ǟ1:1) to give 35 (24 mg,
Ethyl 2,3,3Ј-Tri-O-acetyl-β-D-apiofuranosyl-(1Ǟ3)-2,4-di-O-benz-
oyl-β- -xylopyranosyl-(1Ǟ4)-2,3-O-isopropylidene-1-thio-α-
D
L-rham-
noside (33): A suspension of imidate 32 (169 mg, 0.22 mmol), ethyl
2,3-O-isopropylidene-1-thio-α--rhamnoside (59 mg, 0.24 mmol)
1
91%) as a white foam: [α]2D1 ϭ Ϫ53.0 (c ϭ 1.2, CHCl3). H NMR
(600 MHz, CDCl3): δ ϭ 1.31Ϫ1.34 (m, 9 H), 1.49 (s, 3 H), 1.74 (s,
3 H), 1.88 (s, 3 H), 1.90 (s, 3 H), 1.97 (s, 3 H), 2.09 (s, 3 H), 3.61
(dd, J ϭ 12.3, 6.0 Hz, 1 H), 3.72 (m, 2 H), 3.84 (dd, J ϭ 6.5, 3.9 Hz,
1 H), 3.93Ϫ4.01 (m, 4 H), 4.11Ϫ4.19 (m, 3 H), 4.28Ϫ4.34 (m, 3
H), 4.58 (d, J ϭ 12.3 Hz, 1 H), 4.82 (d, J ϭ 3.9 Hz, 1 H), 4.91 (d,
J ϭ 5.0 Hz, 1 H), 5.02 (s, 1 H), 5.12Ϫ5.23 (m, 6 H), 5.31 (m, 2 H),
5.87 (m, 1 H), 7.37Ϫ8.07 (m, 10 H) ppm. 13C NMR (75 MHz,
CDCl3) δ ϭ 170.3, 169.8, 169.5, 169.0, 168.4, 165.4, 164.6, 133.6,
133.4, 133.3, 129.8, 129.7, 129.3, 128.4, 128.3, 117.8, 108.8, 106.2,
100.3, 97.8, 96.9, 83.5, 76.2, 75.8, 75.5, 72.4, 71.9, 71.8, 69.9, 68.6,
67.1, 63.1, 62.5, 61.8, 28.3, 26.4, 20.9, 20.8, 20.5, 20.0, 17.9,
16.2 ppm. ESI MS: m/z ϭ 1095 [M ϩ Naϩ], 1118 [M ϩ 2Naϩ].
C52H64O24 (1073.1): calcd. C 58.21, H 6.01; found C 58.06, H 5.82.
˚
and activated powdered molecular sieves (4 A, 200 mg) in CH2Cl2
(6 mL) was stirred at room temperature for 15 min and then cooled
to Ϫ50 °C, and a solution of TMSOTf (0.88 mL, 0.05 ) in CH2Cl2
was slowly added. After stirring for 30 min, the reaction mixture
was quenched with Et3N, and filtered. The filtrates were concen-
trated in vacuo to give a residue, which was purified by flash col-
umn chromatography (petroleum ether/EtOAc, 3:1) to yield the
title compound 33 (165 mg, 88%) as a white foam: [α]2D1 ϭ Ϫ137.2
(c ϭ 0.4, CHCl3). 1H NMR (600 MHz, CDCl3): δ ϭ 1.26Ϫ1.32
(m, 9 H), 1.54 (s, 3 H), 1.77 (s, 3 H), 1.91 (s, 3 H), 1.99 (s, 3 H),
2.50 (m, 1 H), 2.62 (m, 1 H), 3.59 (m, 2 H), 3.93Ϫ4.06 (m, 5 H),
4.20 (t, J ϭ 7.2 Hz, 1 H), 4.27 (dd, J ϭ 12.0, 4.8 Hz, 1 H), 4.35
and 4.61 (AB peak, J ϭ 12.0 Hz, 2 H), 5.21 (m, 4 H), 5.25 (s, 1
H), 5.47 (s, 1 H), 7.41Ϫ8.06 (m, 10 H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 169.6, 168.8, 167.8, 164.8, 164.3, 132.6, 132.4, 129.3,
129.1, 127.7, 127.6, 108.6, 105.5, 98.4, 83.0, 78.7, 77.3, 75.7, 75.4,
71.7, 71.2, 69.1, 64.0, 61.9, 61.0, 27.3, 25.7, 23.7, 20.3, 19.9, 19.4,
16.9, 13.9 ppm. EI MS: m/z ϭ 786, 728, 599, 322, 259. C41H50O17S
(846.9): calcd. C 58.15, H 5.95; found C 58.32, H 5.93.
2,3,3Ј-Tri-O-Acetyl-β-
xylopyranosyl-(1Ǟ4)-2,3-di-O-acetyl-α-
isopropylidene-α/β- -fucopyranose (36):
D
-apiofuranosyl-(1Ǟ3)-2,4-di-O-benzoyl-β-
-rhamnosyl-(1Ǟ2)-3,4-O-
I(CF2)8F (50 mg,
D-
L
D
0.11 mmol) was added to a stirred solution of 35 (39 mg, 36 µmol)
in CH3CN/H2O (2:1, 1.5 mL) followed by addition of a mixture
of Na2S2O4 (42 mg, 0.24 mmol) and NaHCO3 (28 mg, 0.33 mmol).
After stirring at room temperature for 10 min, the reaction mixture
Ethyl 2,3,3Ј-Tri-O-acetyl-β-D-apiofuranosyl-(1Ǟ3)-2,4-di-O-benz-
oyl-β- -xylopyranosyl-(1Ǟ4)-2,3-di-O-acetyl-1-thio-α-L-rhamnoside was diluted with EtOAc, washed with brine, dried with MgSO4 and
D
(34): A solution of 33 (361 mg, 0.43 mmol) in HOAc (80%, 10 mL)
was stirred at 50 °C overnight and then concentrated in vacuo, and
concentrated under vacuum. The residue was dissolved in dry
EtOH (4 mL), Zn dust (26 mg, 0.4 mmol) and NH4Cl (13 mg,
972
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 965Ϫ973

Synthesis of Trisaccharide and Tetrasaccharide Moieties
FULL PAPER
Z. Yang, W. Lin, B. Yu, Carbohydr. Res. 2000, 329, 879Ϫ884.
S. Rio, J. M. Beau, J. C. Jacquinet, Carbohydr. Res. 1991, 219,
71Ϫ90.
[13]
[14]
0.24 mmol) were added, and the resulting mixture was heated at
reflux for 50 min and then filtered. The filtrates were concentrated
to give a residue, which was purified by flash column chromatogra-
phy (petroleum ether/EtOAc, 1:1) to furnish the desired hemiacetal
[15]
[16]
[17]
R. R. Schmidt, M. Stumpp, Liebigs Ann. Chem. 1983, 7,
1249Ϫ1256.
1
36 (21 mg, 57%) as an α/β mixture: H NMR (300 MHz, CDCl3):
A. Toepfer, W. Kinzy, R. R. Schmidt, Liebigs Ann. Chem.
1994, 449Ϫ464.
δ ϭ 1.30Ϫ1.60 (m, 12 H), 2.08 (m, 15 H), 3.62Ϫ4.82 (m, 14 H),
5.02Ϫ5.40 (m, 8 H), 7.20Ϫ8.03 (m, 10 H) ppm. ESI MS: m/z ϭ
1055 [M ϩ Naϩ], 1078 [M ϩ 2Naϩ]. C49H60O24·1.5H2O (1060.0):
calcd. C 55.52, H 5.99; found C 55.41, H 5.86.
Ortho ester formation during glycosidation reactions is not un-
usual, for two recent examples with 5 as glycosyl donor, see:
[17a]
H. Amer, A. Hofinger, P. Kosma, Carbohydr. Res. 2003,
338, 35Ϫ45. [17b] W. J. Sanders, D. D. Manning, K. M. Koeller,
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T. Yoshida, T. Chiba, T. Yokochi, K. Onozaki, T. Sugiyama, I.
Nakashima, Carbohydr. Res. 2001, 335, 167Ϫ180.
R. R. Schmidt, Angew. Chem. 1986, 98, 213Ϫ236; Angew.
Chem. Int. Ed. Engl. 1986, 25, 212Ϫ235.
Acknowledgments
We are grateful for financial support from the National Natural
Science Foundation of China (Grant 29925203) and the German
Fonds der Chemischen Industrie.
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[19]
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