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HO
OH
O
HO
O
8
D
-glucose
1-octanol (1.5 equiv)
FeCl
3
(3 equiv)
THF or 1,4-dioxane
OH
13
, 72%
D
-galactose
9
HO
O
O
HO
OH
HO
14
, 60%
Scheme 4 Glycosylation of unprotected hexoses with the ferric chloride-modified
version.
O
H
N
HO
O
O
O
N
P
P
O
O
HO
O
O
O
O
O
OH
15
HO
HO
OH
steps,
ref. 20
HO
O
OMe
HO
OH
12
HO
steps,
ref. 21
HO
OH
O
HO
OH
O
HO
O
O
HO
OR
O
O
O
n
HO
HO
HO
OH
HO
OH
HO
16
, n = 1
17
, n = 2
Scheme 5 Synthesis of hexofuranoside-containing compounds starting from furanoside 12.
chloride-catalyzed glycosylation in a route to UDP-a-
D
-galactofuranose 15
that was developed by Marlow and Kiessling (scheme 5).
20
The sugar nucleotide 15 is the biosynthetic glycosyl donor used in the
incorporation of galactofuranose motifs in glycoconjugates and poly-
saccharides produced by pathogenic microorganisms. The same residue
is found in the repeating unit of the O-polysaccharide of the lipopoly-
saccharide of pathogenic Gram-negative bacteria Klebsiella pneumonia.
With the purpose of studying structure-activity relationships, Zhu and
Yang described the preparation of linear tetra- and hexa-saccharides
16-17 which began with the same step (Scheme 5).
21
3 Iron(
III
) chloride hexahydrate-promoted cascade
cyclization to bioactive dihydropyrans
An iron-promoted cascade cyclization to dihydropyran motifs was dis-
covered while preparing zanamivir analogues and other probes useful in
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