Glycosyl Halides
3.1
433
Alternatively, Sasaki et al. [31] provided a glycosylation method using glycosyl bromide in
the presence of hindered amines such as 2,6-lutidine or TMU under high-pressure conditions
( > Scheme 1). In addition, Nishizawa et al. [32] developed a thermal glycosylation of glycosyl
chloride in the presence of α-methylstyrene or TMU as an acid scavenger without any metal
salts ( > Scheme 2).
2 Chemical Glycosylation of Glycosyl Iodide
Among the glycosyl halides, only a few examples of the use of glycosyl iodide as an isolatable glycosyl donor are demonstrated due to their instability ( > Table 4). Thus, LiClO 4 [33],
TBAI-DIEA [34], FeCl 3 -I 2 [35], CuCl-I 2 [35], and NIS-I 2 -TMSOTf [35] were reported as the
activators of the glycosyl iodides ( > Scheme 3).
⊡ Table 4
Glycosylation of glycosyl iodide
Activator
X
Ref.
LiClO 4
H
[33]
TBAI-DIPEA
H
[34]
NIS-I 2 -TMSOTf
H
[35]
FeCl 3 -I 2
H
[35]
CuCl-I 2
H
[35]
⊡ Scheme 3
3 Preparation and Chemical Glycosylation of Glycosyl Fluoride
3.1 Preparation of Glycosyl Fluoride
Glycosyl fluorides have been widely and effectively used for glycosylation reactions. One of
the notable advantages of the glycosyl fluoride as a glycosyl donor is its higher thermal and
chemical stability as compared to other glycosyl halides such as glycosyl chlorides, bromides,