Highly efficient synthesis of the mannose nonasaccharide of the N-glycan expressed on the HIV glycoprotein gp 120

Article abstract of DOI:10.1055/s-2001-16062

A highly concise and effective synthesis of the mannose nonasaccharide of the glycan expressed on the HIV protein gp 120 was achieved via TMSOTf promoted selective 6-glycosylation of a tetrasaccharide 4,6-diol acceptor with a pentasaccharide donor followed by deprotection. The pentasaccharide was constructed by selective 3,6-diglycosylation of 1,2-O-ethylidene-β-D-mannopyranose with 2-O-acetyl-3,4,6-tri-O-benzoyl-α-D-mannopyranosyl-(1→2)-3,4,6- tri-O-benzoyl-α-D-mannopyranosyl trichloroimidate while the tetrasaccharide was obtained by selective 3-O-glycosylation of allyl 4,6-O-benzilidene-α-D-mannopyranoside with 2,3,4,6-tetra-O-benzoyl-α-D-mannopyranosyl-(1→2)-3,4,6-tri-O- benzoyl-α-D-mannopyranosyl-(1→2)-3,4,6-tri-O-benzoyl-α-D- mannopyranosyl trichloroimidate.

Full text of DOI:10.1055/s-2001-16062

LETTER
1217
Highly Efficient Synthesis of the Mannose Nonasaccharide of the N-Glycan
Expressed on the HIV Glycoprotein gp 120
Yuliang Zhu, Fanzuo Kong*
Research Center for Eco-Environmental Sciences, Academia Sinica, P. O. Box 2871, Beijing 100085, P. R.China
Fax 86-10-62923563; E-mail: fzkong@mail.rcees.ac.cn
Received
Abstract: A highly concise and effective synthesis of the mannose
nonasaccharide of the glycan expressed on the HIV protein gp 120
was achieved via TMSOTf promoted selective 6-glycosylation of
a tetrasaccharide 4,6-diol acceptor with a pentasaccharide donor
followed by deprotection. The pentasaccharide was constructed by
selective 3,6-diglycosylation of 1,2-O-ethylidene- -D-mannopyra-
nose with 2-O-acetyl-3,4,6-tri-O-benzoyl- -D-mannopyranosyl-
(1 2)-3,4,6-tri-O-benzoyl- -D-mannopyranosyl trichloroimidate
while the tetrasaccharide was obtained by selective 3-O-glycosyla-
tion of allyl 4,6-O-benzilidene- -D-mannopyranoside with 2,3,4,6-
tetra-O-benzoyl- -D-mannopyranosyl-(1 2)-3,4,6-tri-O-benzoyl-
-D-mannopyranosyl-(1 2)-3,4,6-tri-O-benzoyl- -D-mannopyra-
nosyl trichloroimidate.
Key words: regio- and stereoselective synthesis, mannopyranosyl
oligosaccharides
AIDS (Acquired Immunodeficiency Syndrome) is a seri-
ous disease imperiling millions people lives in the world.
Despite great research efforts, the viral infection caused
Scheme 1
by the human immunodeficiency virus (HIV) remains in-
curable. The glycosylated surface of glycoprotein gp 120
has a critical role for HIV infection of cells. Gp 120 is es-
pling of the benzoylated mannosyl trichloroimidate 7 with
5 yielded the trisaccharide 8, its deallylation and subse-
quent trichloroimidation afforded the trisaccharide donor
glycans of the viral envelope may be useful for immuno-
sential not only for the attachment and penetration of tar-
get cells, but also for the antiviral immune response. The
therapy or vaccine development.1 A variety of N-linked
oligosaccharides have been identified, the main fraction
being a ubiquitous undecasaccharide A.2 The synthesis of
major segments of high mannose glycoproteins has been
reported3 and a new method for the preparation of the
model nonasaccharide with cyclohexane-1,2-diacetal in-
termediates has been described.4 In continuation of our ef-
fort towards regio- and stereoselective synthesis of
bioactive oligosaccharides, we report herewith a highly
efficient and concise synthesis of the nonasaccharide B of
the N-glycan expressed on the glycoprotein gp 120.
9. Condensation of 9 with allyl 4,6-O-benzylidene -D-
mannopyranoside (10) selectively gave 3-linked tetrasac-
charide 11. Acetylation of 11 confirmed the 3-glycosyla-
tion as the 1H NMR spectrum of acetylated
tetrasaccharide 12 showed a newly emerged doublet of
doublets at 5.52 ppm for H-2. Debenzylidenation was
carried out readily with CH3COCl-CH3OH (0.1% v/v)
giving the terasaccharide acceptor 13 with 4,6-free OH.
The pentasaccharide donor was obtained readily by regi-
oselective glycosylation through orthoester intermedi-
ates.6 Thus coupling of 2.2 equiv of the disaccharide
trichloroimidate 6 with 1 equiv of 1,2-O-ethylidene- -D-
mannopyranose (14) promoted by TMSOTf gave 3,6-
branched pentasaccharide 15 in good yield (86%). The
3,6-selective glycosylation was confirmed by acetylation
of 15, and the 1H NMR spectrum of the acetylated product
16 showed a characteristic triplet for H-4 at 5.20 ppm. It
was noted that the temperature at addition of TMSOTf
was maitained below 20 °C to ensure orthoester to be the
intermediate.7 Otherwise, for example at room tempera-
ture, the regioselectivity will be lost producing 3,4,6-trig-
lycosylated heptasaccharide as the major one.
Deethylidenation of 16 with 90% CF3COOH, acetylation
Scheme 2 outlines the synthetic route. The key intermedi-
ate mannose 1,2-allyl orthoester 3 was readily prepared in
large scales by reaction of acetylated mannosyl bromide 1
with allyl alcohol in the presence of 2,4-lutidine, then
Zemplén deacetyaltion with MeONa/MeOH, and benzoy-
lation with benzoyl chloride in pyridine. Self condensa-
tion of 3 produced the disaccharide 4 in a satisfactory
yield (66%). Selective removal of 2-O-acetyl from 4 af-
forded the disaccharide acceptor 5, while deallylation of 4
with PdCl2 followed by activation with CCl3CN in the
presence of K2CO3 gave the disaccharide donor 6.5 Cou-
Synlett 2001, No. 8, 1217–1220 ISSN 0936-5214 © Thieme Stuttgart · New York

1218
Y. Zhu, F. Kong
LETTER
Scheme 2 Conditions and reagents: a: lutidine, CH2Cl2, 4Å M.S., 4 h, then MeONa, MeOH; b: BzCl/pyridine (dry); c: TMSOTf, CH2Cl2, 4Å
M.S., N2, -20 °C to rt, 4 h; d: CH3OH, CH3COCl (5%, V/V); e: PdCl2, CH2Cl2, 2 h; f: CCl3CN, DBU, CH2Cl2 8 h; g: Ac2O/Pyridine (dry), rt,
6 h; h: CH3OH, CH3COCl (0.1%, V/V); i: 90% CF3COOH, rt, 2-5 h; j: DMF, (NH4)2CO3, rt, 4-8 h; k: NH3/MeOH.
with acetic anhydride in pyridine, trichloroimidation with 4057.16 (cald. 4057.36) and the 13C NMR spectrum of 20
CCl3CN in the presence of DBU or K2CO3 gave the pen- gave 9 signals for C-1 from 95.7-100.9 ppm with 2JC1-H1
tasaccharide donor 18 (82% from 16). With the pentasac- from 170-174 Hz indicating complete -linkages. Finally,
charide donor and tetrasaccharide acceptor at hand, deacylation of 20 in ammonia-saturated methanol gave
selective 6-glycosylation7 was readily carried out giving the target nonasaccharide 21.8
the nonasaccharide 19 in acceptable yield (84%). Acety-
In summary, a highly efficient and concise synthesis of
lation with acetic anhydride in pyridine, purification by
the mannose nonasaccharide of the N-glycan expressed
column chromatography afforded fully protected nona-
on protein gp 120 was achieved by regio- and stereoselec-
saccharide 20. The MS spectrum of 20 showed M+ at
Synlett 2001, No. 8, 1217–1220 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Highly Efficient Synthesis of the Mannose Nonasaccharide
1219
diluted with dichloromethane, washed with 1 N hydrochloric
acid, water, and saturated aqueous solution of sodium
bicarbonate subsequently. The organic layers were combined,
dried, and concentrated. Purification by column
tive glycosylation using glycosyl trichloroimidates as the
donors and partially protected sugars as the acceptors. In
terms of the simplicity and efficiency, this method will be
useful for the synthesis of high mannose oligosaccharides.
chromatography (2:1 petroleum ether-ethyl acetate) gave 12
quantitatively as colorless crystals; mp 138-140 °C; [ ]D
5.6o (c 1.1, CHCl3); 13C NMR 170.31, (1 CH3CO), 166.34,
165,92, 165.73, 165.60, 165.43, 165.25, 165.20, 165.15,
164.91, 164.64, (10C6H5CO), 99.98, 99.67, 99.05, 97.69, (C-
1I-IV), 79.17 (C-3), 71.18, 71.09, 70.33, 70.25, 70.00, 69.72,
69.63, 69.52, 68.60, 68.32, 66.79, 66.42, 63.68, 63.38, 62.95,
62.59, (C-2,3,4,5,6I-IV, some signals were overlapped); 1H
NMR 8.07-7.24 (m, 50 H, Bz-H), 6.00-5.88 (m, 5 H), 5.88-
5.77 (m, 1 H, CH2=CH-CH2-), 5.75 (dd, 1 H, J = 3.2 Hz,
J = 1.6 Hz), 5.65 (dd, 1 H, J = 3.1 Hz, J = 10.0 Hz), 5.61 (s, 1
H), 5.52 (dd, 1 H, J = 3.2 Hz, J = 1.5 Hz), 5.36 (s, 2 H), 5.30
(dd, 1 H, CH2=CH-CH2), 5.24 (dd, 1 H, CH2=CH-CH2), 4.93
(s, 1 H), 4.86 (s, 1 H), 4.64-4.58 (m, 3 H), 4.53 (dd, 1 H,
J = 3.2 Hz, J = 10.0 Hz), 4.52-4.48 (m, 1 H), 4.43 (dd, 1 H,
J = 3.1 Hz, J = 10.0 Hz), 4.30-4.20 (m, 3 H), 4.16-4.09 (m, 3
H), 4.07-3.95 (m, 5 H), 3.77 (t, 1 H, J = 10.0 Hz), 2.35 (s, 3 H,
CH3CO). For 13: To a solution of 12 (1876 mg, 1 mmol) in
methyl alcohol (50 mL) acetyl chloride (0.05 mL, 0.7 mmol)
was added dropwise, and the mixture was stirred overnight at
room temperature. TLC (1.5:1 petroleum ether-ethyl acetate)
indicated that the reaction was complete. The mixture was
concentrated. Purification by column chromatography (1.5:1
petroleum ether-ethyl acetate) gave 13 (1628 mmg, 91%) as a
colorless solid; [ ]D 4.4o (c 1.2, CHCl3); 13C NMR 170.22,
(CH3CO), 167.60, 167.23, 166.40, 166.15, 165.43, 165.43,
165.40, 165.32, 165.20, 165.15, (10C6H5CO), 99.56, 99.36,
99.06, 98.98, (C-1I-IV), 76.45, (C-3), 72.39, 70.16, 70.06,
69.90, 69.64, 69.32, 69.01, 68.63, 67.97, 67.56, 66.49, 63.88,
63.76, 63.51, 62.31, 55.04, (C-2,3,4,5,6I-IV, some signals were
overlapped); 1H NMR 8.11-7.26 (m, 50 H, Bz-H), 6.11 (t, 1
H, J = 9.9 Hz), 6.07 (t, 1 H, J = 10.0 Hz), 5.95-5.85 (m, 3 H),
5.85-5.80 (m, 1H, CH2=CH-CH2), 5.76 (dd, 1 H, J = 3.0 Hz,
J = 1.5 Hz), 5.71 (d, 1 H, J = 1.6 Hz), 5.69 (dd, 1 H, J = 3.0 Hz,
J = 10.0 Hz), 5.51 (s, 1 H), 5.38 (dd, 1 H, J = 3.0 Hz, J = 1.6
Hz), 5.31 (dd, 1 H, CH2=CH-CH2), 5.20 (dd, 1 H, CH2=CH-
CH2), 5.02 (s, 1 H), 4.84 (d, 1 H, J 1.4 Hz), 4.63-4.51 (m, 9 H),
4.39 (dd, 1 H, J = 3.0 Hz, J = 1.5 Hz), 4.25 (dd, 1 H, J = 3.0
Hz, J = 10.0 Hz), 4.23-4.14 (m, 3 H), 4.00 (dd, 1 H), 3.89 (m,
2 H), 3.67-3.64 (m, 1 H), 2.18 (s, 3 H, CH3CO). For 15: The
disaccharide donor 6 (1268 mg, 1.1 mmol) and the
Acknowledgement
This work was supported by The Chinese Academy of Sciences
(Projects KJ952J1510 and RCEES9904) and by The National Natu-
ral Science Foundation of China (Projects 29802009, 30070185,
and 39970864).
References and Notes
(1) a) J. E. S. Hansen, H. Clausen, C. Nielsen, L. S. Teglbjaerg,
L. L. Hansen, C. M. Nielsen, E. Dabelsteen, L. Mathiesen, S.-
i. Hakomori, J.O. Nielsen, J. Virol. 1990, 64, 2833-2840. b) J.
E. S. Hansen, C. Nielsen, M. Arendrup, S. Olofsson, L.
Mathiesen, J.O. Nielsen, H. Clausen, J. Virol. 1991, 65, 6461-
6467. c) J. E. S. Hansen, H. Clausen, T. Sorensen, T. White,
H. H. Wandall, Alfred Benzon Symp. 1994, 36, 297-310. d) J.
E. S. Hansen, B. Hoffman, T. Sorensen, H. Clausen, Alfred
Benzon Symp. 1994, 36, 414-427.
(2) a) H. Lis, N. Sharon, J. Biol. Chem. 1978, 253, 3468-3473.
b) E. Li, S. Kornfeld, J. Biol. Chem. 1979, 254, 1600-1606.
c) L. Dorland, H. van Halbeek, J. F. G. Vliegenthart, H. Lis,
N. Sharon, J. Biol. Chem. 1981, 256, 7708-7714.
(3) a) H. Paulsen, Angew. Chem. Int. Ed. Engl. 1990, 29, 823-827
and references therein. b) J. R. Merritt, E. Naisang, B. Fraser-
Reid, J. Org. Chem. 1994, 59, 4443-4449. c) Y. Nakahara, S.
Shibayama, Y. Nakahara, T. Ogawa, Carbohydr. Res. 1996,
280, 67-84.
(4) P. Grice, S. V. Ley, J. Pietruszka, H. W. M. Priepke, Angew.
Chem. Int. Ed. Engl. 1996, 35, 197-200.
(5) Y. Zhu, F. Kong, Synlett. 2001, 1783-1788.
(6) a)W. Wang, F. Kong, J. Org. Chem. 1998, 63, 5744-5745.
b) W. Wang, F. Kong, Angew. Chem. Int. Ed. Engl. 1999, 38,
1247-1250.
(7) Y. Zhu, F. Kong, Synlett. 2001, 663-667.
(8) All of the new compounds were identified by 1H, 13C NMR,
optical rotations, and elemental analysis. Selected physical
data and preparations for some important compounds are
presented below. For 11: The trisaccharide donor 9 (1677 mg,
1 mmol) and the monosaccharide acceptor 10 (308 mg, 1
mmol) were dried together under high vacuum for 2 h, then
dissolved in anhydrous dichloromethane (50 mL). TMSOTf
(15 L, 0.08 equiv) was added dropwise at 20 C with N2
protection. The reaction mixture was stirred for 2 h, during
which time the reaction temperature gradually raised to
ambient temperature. Then the mixture was neutralized with
triethylamine, concentrated under reduced pressure to an oily
residue. Purification by column chromatography (1:1.5
petroleum ether-ethyl acetate) gave 11 (1651 mg, 90%) as
colorless crystals; mp 131-133 °C; [ ]D 11.5o (c 1.1, CHCl3);
1H NMR 8.07-7.24 (m, 50 H, Bz-H), 6.03 (t, 1 H, J = 9.9
Hz), 5.95-5.90 (m, 3 H), 5.81-5.76 (m, 3 H), 5.73 (d, 1 H,
J = 1.6 Hz), 5.58 (s, 1 H, Ph-C-H), 5.55 (dd, 1 H, J = 3.1 Hz,
J = 1.5 Hz), 5.45 (s, 1 H), 5.28 (dd, 1 H, CH2 = CH-CH2), 5.20
(dd, 1 H, CH2 = CH-CH2), 5.02 (s, 1 H), 4.93 (s, 1 H), 4.62 (dd,
1 H), 4.55-4.45 (m, 2 H), 4.43-4.33 (m, 4 H), 4.30-4.17 (m, 8
H), 4.05-3.97 (m, 2 H), 3.90-3.85 (m, 1 H), 3.81 (t, 1 H,
J = 10.0 Hz). For 12: To a solution of 11 (1834 mg, 1 mmol)
in pyridine (30 mL) acetic anhydrate (1 mL, 10 mmol) was
added dropwise, and the mixture was stirred overnight at room
temperature. TLC (1.5:1 petroleum ether-ethyl acetate)
indicated that the reaction was complete. The mixture was
monosaccharide acceptor 14 (103 mg, 0.5 mmol) were dried
together under high vacuum for 2 h, then dissolved in
anhydrous dichloromethane (30 mL). TMSOTf (15 L, 0.08
equiv) was added dropwise at 20 C with N2 protection. The
reaction mixture was stirred for 3 h, during which time the
reaction temperature gradually raised to ambient temperature.
Then the mixture was neutralized with triethylamine,
concentrated under reduced pressure to an oily residue.
Purification by column chromatography (1:1.5 petroleum
ether-ethyl acetate) gave 15 (940 mg, 86%) as a colorless
solid; mp 141-144 °C; [ ]D 11.5o (c 1.1, CHCl3); 1H NMR
7.98-7.25 (m, 60 H, Bz-H), 6.03-5.85 (m, 8 H), 5.67 (dd, 1 H,
J = 3.0 Hz, J = 1.7 Hz), 5.64 (dd, 1 H, J = 3.1 Hz, J = 1.7 Hz),
5.53 (s, 1 H), 5.26 (q, 1 H, CH3-CH), 5.20 (s, 1 H), 5.12 (d, 1
H, J = 1.6 Hz), 5.08 (d, 1 H, J = 1.7 Hz), 5.05 (d, 1 H, J = 1.7
Hz), 4.60-4.46 (m, 13 H), 4.42 (dd, 1 H, J = 3.0 Hz, J = 1.7
Hz), 4.20 (dd, 1 H, J = 3.0 Hz, J = 1.7 Hz), 4.04 (t, 1 H,
J = 10.0 Hz), 3.98-3.94 (m, 1 H), 3.83 (dd, 1 H, J = 3.2 Hz,
J = 10.0 Hz), 3.75-3.68 (m, 1 H), 3.41-3.37 (m, 1 H), 2.01 (s,
3 H, CH3CO), 2.00 (s, 3 H, CH3CO), 1.50 (d, 3 H, CH3-CH).
For 17: 16 (2228 mg, 1 mmol) was treated with 90%
F3CCOOH (10 mL) at room temperature for 1 h, the solution
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1220
Y. Zhu, F. Kong
LETTER
under reduced pressure to an oily residue. Purification by
was concentrated and co-concentrated with toluene. The
residue was dissolved in pyridine (10 mL) and treated with
Ac2O (3 mL) for 2 h. After conventional work-up, the residue
was subjected to column chromatography (1.5/1 petroleum
ether/EtOAc) to yield 2-O-acetyl-3,4,6-tri-O-benzoyl- -D-
mannopyranosyl-(1 2)-3,4,6-tri-O-benzoyl- -D-
mannopyranosyl-(1 3)-[-2-O-acetyl-3,4,6-tri-O-benzoyl- -
D-mannopyranosyl-(1 2)-3,4,6-tri-O-benzoyl- -D-
mannopyranosyl-(1 6)]-1,2,4-tri-O-acetyl- , -D-
mannopyranose as a solid (1941 mg, 85%). A solution of the
solid (1142 mg, 0.5 mmol), ammonium carbonate (790 mg, 10
mmol) in DMF (20 mL) was stirred for 12 h at r.t. At the end
of which time TLC (2/1 petroleum ether/EtOAc) showed that
the reaction was complete. Water was added, and the mixture
was diluted with dichloromethane, washed with 1 N
hydrochloric acid, water, and sat. aq. solution of sodium
bicarbonate subsequently. The organic layer was combined,
dried, and concentrated. The obtained residue was passed
through a short silica gel column with 2/1 petroleum ether/
ethyl acetate as the eluent to give 17 as a solid consisting of
anomer predominantly (1021 mg, 91%),: [ ]D 13.2o (c 1.1,
CHCl3); 13C NMR 170.52, 170.04, 169.31, 169.26,
(4CH3CO), 166.66, 166.53, 166.45, 166.15, 165.70, 165.67,
165.65, 165.55, 165.42, 165.28, 165.11, 164.98, (12C6H5CO),
100.47, 99.76, 99.36, 98.97, 92.36 (C-1I-V), 79.08 (C-3),
77.28, 77.28 (C-2), 72.86, 71.32, 70.59, 70.06, 69.94, 69.73,
69.70, 69.67, 69.64, 69.61,69.58, 69.38, 69.11, 68.47, 68.20,
67.49, 67.12, 66.88, 63.97, 63.86, 63.33, 63.04, (C-2,3,4,5,6 I-
V); 1H NMR 8.01-7.26 (m, 60 H, Bz-H), 5.95-5.83 (m, 7 H),
5.70 (dd, 1 H, J = 3.0 Hz, J = 10.0 Hz), 5.64 (dd, 1 H, J = 3.1
Hz, J = 1.5 Hz), 5.60 (dd, 1 H, J = 3.0 Hz, J = 1.5 Hz), 5.49
(dd, 1 H, J = 3.0 Hz, J = 1.5 Hz), 5.40 (s, 1 H), 5.24 (s, 1 H),
5.22 (t, 1 H, J = 10.0 Hz), 5.20 (s, 1 H), 5.08 (s, 1 H), 5.02 (s,
1 H), 4.66-4.37 (m, 14 H), 4.22 (dd, 1 H, J = 3.0 Hz, J = 1.5
Hz), 4.00-3.95 (m, 1H), 3.77-3.73 (dd, 1 H), 3.58-3.55 (m, 1
H), 2.30 (s, 3 H, CH3CO), 2.19 (s, 3 H, CH3CO), 2.01 (s, 3 H,
CH3CO), 2.00 (s, 3 H, CH3CO). For 18: The compound 17
(2244 mg, 1 mmol) was dissolved in dichloromethane (20
mL), then CCl3CN (0.1 ml, 1 mmol) and DBU (14 L, 0.1
mmol) were added. The reaction mixture was stirred for 2 h,
at the end of which time TLC (2/1 petroleum ether/ethyl
acetate) indicated that the reaction was complete.
Concentration of the reaction mixture followed by purification
on a silica gel column with 2/1 petroleum ether/EtOAc as the
eluent furnished the pentasaccharide donor 18 as crystals in a
good yield (2150 mg, 90%): mp 135-137 °C; [ ]D 9.5o (c 1.3,
CHCl3); 1H NMR 9.03 (s, 1 H, C = NH), 8.10-7.26 (m, 60 H,
Bz-H), 6.35 (d, 1 H, J1,2 = 1.5 Hz, H-1), 6.05 (t, 1 H, J = 10.0
Hz), 5.96 (t, 2 H, J = 10.1 Hz), 5.91 (t, 1 H, J = 10.1 Hz), 5.88
(dd, 1 H, J = 3.0 Hz, J = 10.0 Hz), 5.85 (dd, 1 H, J = 3.0 Hz,
J = 10.0 Hz), 5.80 (dd, 1 H, J = 3.0 Hz, J = 10.1 Hz), 5.74 (dd,
1 H, J = 3.0 Hz, J = 10.1 Hz), 5.68-5.66 (m, 2 H), 5.64 (dd, 1
H, J = 3.0 Hz, J = 1.5 Hz), 5.45 (t, 1 H, J = 10.0 Hz), 5.43 (s,
1 H), 5.17 (s, 1 H), 5.09 (s, 2 H), 4.61-4.43 (m, 13 H), 4.33 (dd,
1 H, J = 3.0 Hz, J = 1.5 Hz), 4.30 (dd, 1 H, J = 3.0 Hz, J = 1.5
Hz), 4.22-4.18 (m, 1 H), 3.89-3.84 (m, 1 H), 3.59-3.56 (m, 1
H), 2.26 (s, 3 H, CH3CO), 2.10 (s, 3 H, CH3CO), 2.02 (s, 3 H,
CH3CO), 2.00(s, 3 H, CH3CO). For 19: The pentasaccharide
donor 18 (1193 mg, 0.5 mmol) and the tetrasaccharide
acceptor 13 (894 mg, 0.5 mmol) were dried together under
high vacuum for 2 h, then dissolved in anhydrous
column chromatography (1:1 petroleum ether-ethyl acetate)
gave 19 (1606 mg, 80%) as a colorless solid; [ ]D 4.8o (c 1.0,
CHCl3); 1H NMR 8.10-7.26 (m, 110 H, Bz-H), 6.17 (t, 1 H,
J = 9.9 Hz), 6.14-5.70 (m, 13 H), 5.65-5.50 (m, 7 H), 5.42 (s,
1 H), 5.40 (s, 1 H), 5.38 (s, 1 H), 5.35 (dd, 1 H, CH2=CH-CH2),
5.25 (dd, 1 H, CH2=CH-CH2), 5.23 (s, 1 H), 5.18 (s, 2 H), 5.04
(s, 1 H), 4.95 (s, 1 H), 4.84 (s, 1 H), 4.70-4.25 (m, 26 H), 4.20-
4.10 (m, 4 H), 4.03-3.98 (m, 2 H), 3.85-3.78 (m, 2 H), 3.65-
3.61 (m, 1 H), 3.55-3.51 (m, 1 H), 2.27 (s, 3 H, CH3CO), 2.18
(s, 3 H, CH3CO), 2.12 (s, 3 H, CH3CO), 2.00 (s, 3 H, CH3CO),
1.98 (s, 3 H, CH3CO); MALDI-TOF MS Calcd for
C221H194O73: 4015.15 [M]. Found: 4015.39 [M]. For 20: To a
solution of 19 (1204 mg, 0.3 mmol) in pyridine (20 mL) acetic
anhydrate (1 mL, 10 mmol) was added dropwise, and the
mixture was stirred overnight at room temperature. TLC
(1.5:1 petroleum ether-ethyl acetate) indicated that the
reaction was complete. The mixture was diluted with
dichloromethane, washed with 1 N hydrochloric acid, water,
and saturated aqueous solution of sodium bicarbonate
subsequently. The organic layers were combined, dried, and
concentrated. Purification by column chromatography (1.5:1
petroleum ether-ethyl acetate) gave 20 quantitatively as a
colorless solid; [ ]D 2.5o (c 1.0, CHCl3); 13C NMR 170.10,
170.06, 169.56, 169.31, 168.79, 168.70, (6CH3CO), 165.99,
165.93, 165.84, 165.75, 165.55, 165.51, 165.41, 165.28,
165.20, 165.14, 165.10, 165.05, 165.01, 164.95, 164.89,
164.78, 164.70, 164.67, 164.56, 164.42, 164.38, 164.27,
(22C6H5CO), 99.94, 99.80, 99.72, 99.50, 99.41, 98.90, 98.18,
97.16, 96.05, (C-1I-IX), 76.85, 76.78, (C-3), 73.43, 73.25,
70.53, 70.46, 70.25, 70.08, 69.86, 69.57, 69.32, 69.17, 68.47,
68.24, 68.11, 66.80, 66.76, 66.70, 66.60, 66.54, 66.48, 66.40,
66.30, 66.17, 66.06, 65.81, 63.26, 63.05, 62.64, 62.27, 61.90,
59.93, (C-2,3,4,5,6 I-IX, some signals overlapped); 1H NMR
8.09-7.26 (m, 110 H, Bz-H), 6.09 (t, 1 H, J = 9.9 Hz), 6.06-
5.77 (m, 17 H), 5.68-5.60 (m, 3 H), 5.40 (dd, 1 H, J = 3.0 Hz,
J = 1.5 Hz), 5.38 (s, 1 H), 5.34 (s, 1 H), 5.32 (dd, 1 H,
CH2 = CH-CH2), 5.27 (s, 1 H), 5.26 (dd, 1 H, CH2 = CH-CH2),
5.24 (s, 1 H), 5.21 (s, 1 H), 5.11 (s, 1 H), 5.08 (s, 1 H), 5.02 (s,
1 H), 4.88 (s, 1 H), 4.63-4.42 (m, 20 H), 4.39-4.19 (m, 6 H),
4.16-4.00 (m, 5 H), 3.89-3.80 (m, 2 H), 3.60-3.56 (m, 1 H),
3.45-3.40 (m, 1 H), 2.29 (s, 3 H, CH3CO), 2.15 (s, 3 H,
CH3CO), 2.11 (s, 3 H, CH3CO), 2.09 (s, 3 H, CH3CO), 2.00 (s,
6 H, 2CH3CO); MALDI-TOF MS Calcd for C223H196O74:
4057.16 [M]. Found: 4057.36 [M]. For 21: A saturated
solution of ammonia in MeOH (5 mL) was added to a solution
of 20 (811 mg, 0.2 mol) in MeOH (4 mL). After a week at
room temperature, the reaction mixture was concentrated and
the residue was purified by chromatography on Sephadex LH-
20 (MeOH) to afford 21 (243 mg, 80%) as a syrup; 13C NMR
136.22, 118.17 (CH2=CH-CH2), 104.32, 104.32, 104.32,
102.83, 102.83, 102.72, 102.72, 101.24, 100.10, (C-1I-IX),
80.73, 80.54, (C-3), 72.85, 72.46, 70.70, 70.12, 69.85, 69.56,
69.50, 69.44, 69.32, 69.10, 66.45, 66.32, 66.28, 66.24, 66.09,
65.24, 65.03, 64.76, 64.60, 60.90, 60.68, 60.48, 60.22, 59.96,
58.25, (C-2,3,4,5,6 I-IX, some signals overlapped); 1H NMR
5.90 (m, 1 H, CH2=CH-CH2), 5.30 (s, 1 H), 5.27 (dd, 1 H,
CH2=CH-CH2), 5.24 (s, 1 H), 5.22 (dd, 1 H, CH2=CH-CH2),
5.18 (s, 1 H), 5.05 (s, 1 H), 4.95 (s, 3 H), 4.72 (s, 1 H), 4.68 (s,
1H), 4.05-3.53 (m, 56 H); MALDI-TOF MS Calcd for
C57H96O46: 1516.52 [M]. Found: 1539.27 [M+Na].
dichloromethane (30 mL). TMSOTf (7.5 L, 0.08 equiv) was
added dropwise at 20 C with N2 protection. The reaction
mixture was stirred for 3 h, during which time the reaction
temperature gradually raised to ambient temperature. Then the
mixture was neutralized with triethylamine, concentrated
Article Identifier:
1437-2096,E;2001,0,08,1217,1220,ftx,en;Y08801ST.pdf
Synlett 2001, No. 8, 1217–1220 ISSN 0936-5214 © Thieme Stuttgart · New York