1254
F. Ratajczak et al.
LETTER
Preferential acetylation of the known di-O-acetyl-thio- Coupling of 10 and the donors 16 or 18 led to the expected
galactoside (11)6 by using the 1-acetyloxy-benzotriazole tetrasaccharide 19 and pentasaccharide 20 in 56 and 68%
procedure,7 gave compound 12 in 50% yield. The free hy- yield respectively.10 Whereas 2 was easily obtained from
droxy group of compound 12 was then quantitatively es- the acyl precursor 19 by de-O-acylation under Zemplen
terified with trifluoromethanesulfonic anhydride (Tf2O) conditions,11 the deprotection of 20 was only accom-
in a mixture of CH2Cl2–pyridine. Coupling of the triflate plished in good yield by using guanidine hydrochloride,12
13 and the donor 148 as already described led stereo- due to the precipitation of partially de-O-acetylated com-
specifically to the triphenylmethyl 1,4-dithio-a-maltoside pound in MeONa/MeOH solution.
15, which was then converted into the nucleophilic cou-
pling compound 16 in 59% overall yield. The same
two-step procedure using compounds 13 and 16 gave the
Acknowledgment
This work was funded, in part, by the European Union under con-
tract BIO4-CT98-0022.
expected trisaccharides 17 then 18 in 78 and 96% yield
respectively (Scheme 2).9
References
R2O
OR3
OAc
(1) Driguez, H. ChemBioChem 2001, 2, 311.
(2) Hrmova, M.; De Gori, R.; Smith, B. J.; Fairweather, J. K.;
Driguez, H.; Varghese, J. N.; Fincher, G. B. Plant Cell 2002,
14, 1033.
(3) Blanc-Muesser, M.; Vigne, L.; Driguez, H.; Lehmann, J.;
Steck, J.; Urbahns, K. Carbohydr. Res. 1992, 224, 59.
(4) Quian, M.; Spinelli, S.; Driguez, H.; Payan, F. Protein Sci.
1997, 6, 2285.
O
O
AcO
AcO
AcO
AcO
SR1
AcO
SAc
11 R1 = C(C6H5)3, R2 = R3 = H
12 R1 = C(C6H5)3, R2 = H, R3 = Ac
13 R1 = C(C6H5)3, R2 = Tf, R3= Ac
14
(5) Bennett, S.; von Itzstein, M.; Kiefel, M. J. Carbohydr. Res.
1994, 259, 293.
(6) Blanc-Muesser, M.; Vigne, L.; Driguez, H. Tetrahedron
Lett. 1990, 31, 3869.
(7) Blanc-Muesser, M.; Driguez, H.; Lehmann, J.; Steck, J.
Carbohydr. Res. 1992, 223, 129.
(8) Blanc-Muesser, M.; Defaye, J.; Driguez, H. J. Chem. Soc.,
Perkin Trans. 1 1982, 15.
(9) General Procedure for Coupling Reactions. To a solution
in DMF (1 mL) of freshly prepared triflate (0.04 mmol) was
added 1,4-dithioerytritol (0.04 mmol), the acceptor (0.05
mmol) and at 0 °C diethylamine (0.08 mmol). After stirring
for 40–60 min at r.t., DMF was removed and the residue was
diluted in CH2Cl2, washed with water and purified by flash
chromatography.
OAc
O
AcO
AcO
OAc
O
AcO
S
AcO
AcO
R
13 + 14
15 R = SC(C6H5)3
16 R = SAc
OAc
O
(10) Selected physical and spectroscopic data for key
compounds. Ascending order of roman numerals were
assigned to the residues starting from the reducing end.
Compound 9: [a]D20 = +123 (c = 1.6, CHCl3). 13C NMR (75
MHz, CDCl3): d = 97.1 (C-1I), 84.7 (C-1II), 55.5 (CH3), 45.5
AcO
AcO
OAc
O
AcO
S
OAc
O
AcO
AcO
S
AcO
(C-4I). Compound 16: [a]D20 = +261 (c = 2.6, CHCl3). 13
C
AcO
13 + 16
R
17 R = SC(C6H5)3
18 R = SAc
NMR (75 MHz, CDCl3): d = 82.3 (C-1II), 80.1 (C-1I), 43.3
(C-4I). Compound 18: [a]D20 = +268 (c = 1.8, CHCl3). 13
C
NMR (75 MHz, CDCl3): d = 82.3, 82.4 (C-1II, 1III), 80.1 (C-
1I), 43.6 (C-4I, 4II). Compound 19: [a]D20 = +237 (c = 6.2,
CHCl3). 13C NMR (75 MHz, CDCl3): d = 97.0 (C-1I), 82.6,
83.3, 83.5 (C-1II, 1III, 1IV), 55.4 (CH3), 43.6, 45.5, 45.6 (C-4I,
OAc
O
4II, 4III). Compound 20: [a]D20 = +258 (c = 1.1, CHCl3). 13
C
AcO
OBz
O
AcO
NMR (75 MHz, CDCl3): d = 97.0 (C-1I), 82.5, 82.6, 83.3,
83.5 (C-1II, 1III, 1IV, 1V), 55.4 (CH3), 43.6,43.9, 45.5, 45.6
(C-4I, 4II, 4III, 4IV). Compound 2: 13C NMR (75 MHz, D2O):
d = 99.7 (C-1I), 85.9 (C-1II, 1III, 1IV), 55.4 (CH3), 47.0 (C-4I,
4II, 4III). Compound 3: 13C NMR (75 MHz, D2O): d = 99.7
(C-1I), 86.0, 86.1 (C-1II, 1III, 1IV, 1V), 55.4 (CH3), 47.0 (C-4I,
4II, 4III, 4IV).
AcO
S
OBz
O
BzO
n
BzO
S
BzO
BzO
19 n = 2
20 n = 3
10 + 16
10 + 18
OCH3
Scheme 2
(11) Thompson, A.; Wolfrom, M. L. Methods Carbohydr. Chem.
1963, 2, 215.
(12) Kunesch, N.; Miet, C.; Poisson, J. Tetrahedron Lett. 1987,
28, 3569.
Synlett 2003, No. 9, 1253–1254 ISSN 1234-567-89 © Thieme Stuttgart · New York