910
Y. Cao, H. Yamada / Carbohydrate Research 341 (2006) 909–911
OAc
4
O
AcO
AcO
1
2
3
5
BnO OAc
6
Scheme 2. Corrected simultaneous debenzylation–acetolysis sequence of 1. Reagents and conditions: Ac2O, 1% (v/v) H2SO4, rt.
However, the isolated mono-O-benzylated product was
not the tetraacetate of the 4-O-benzylated glucose 4 as
reported, but the 2-O-benzylated tetraacetate 6 (Scheme
2). The structure of 6 was confirmed by comparing the
NMR data to that reported in the literature after HPLC
separation of the anomeric mixture into the pure a and b
anomers (6a and 6b, respectively).11 Comparison of
Sakai’s 13C NMR data with ours revealed that the com-
pound we isolated as 6a was identical with the com-
pound they isolated as 4 (a anomer).8a Consequently,
the sequence of the simultaneous debenzylation–acetol-
ysis should be corrected as 6-O-Bn > 3-O-Bn > 4-O-
Bn > 2-O-Bn.
tific Research on Priority Areas (17035086) from
MEXT.
Supplementary data
Supplementary data is available for this paper: Charac-
1
terization data and copies of H and 13C NMR spectra
for both a and b isomers of compounds 2, 3, and 6. Sup-
plementary data associated with this article can be
In summary, the benzyl groups of methyl 2,3,4,6-
tetra-O-benzyl-a-D-glucopyranoside (1) were stepwise
cleaved in the order of 6-O-Bn > 3-O-Bn > 4-O-Bn > 2-
O-Bn under acid-mediated acetolysis conditions in ace-
tic anhydride. This should serve as basic knowledge
for preparation of partly benzylated sugar compounds
that are known or potential building blocks, not only
for more complex sugar compounds, but also for opti-
cally active natural products.12
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