368
2
General Synthetic Methods
⊡ Scheme 41
C-glycosyl phosphonates are important inhibitors of enzymes [87]. An interesting approach to
such derivatives was proposed recently [88].
The synthesis was initiated from the unsaturated phosphonate 95 prepared in several steps
from the D-glucal as shown in > Scheme 41. The 1,4-addition of a soft nucleophile provided
the adduct which, upon acetylation, was easily converted into the target 96.
An interesting approach to symmetrical C-disaccharides was proposed recently by Lowary.
1-O-Acetyl-sugar 97 was converted into 1-C-allyl derivative 97a by classical reaction with
allyltrimethylsilane, and this derivative was ‘dimerized’ under the metathesis conditions with
Grubbs’ catalyst ( > Scheme 42) [89].
Unsaturated sugars are used also as starting materials for the preparation of complex natural
products and their analogs. For example, radical cyclization of 98 (readily prepared in well
defined steps from D-glucal) led to synthon 99, a precursor of antifungal agent GM222712
(a close analog of sordarin) [90]. The cascade reaction of 100 with the nucleophile catalyzed
with gold-III provided also the bicyclic skeleton with a different arrangement of unsaturated
bonds ( > Scheme 43) [91].
⊡ Scheme 42
2
General Synthetic Methods
⊡ Scheme 41
C-glycosyl phosphonates are important inhibitors of enzymes [87]. An interesting approach to
such derivatives was proposed recently [88].
The synthesis was initiated from the unsaturated phosphonate 95 prepared in several steps
from the D-glucal as shown in > Scheme 41. The 1,4-addition of a soft nucleophile provided
the adduct which, upon acetylation, was easily converted into the target 96.
An interesting approach to symmetrical C-disaccharides was proposed recently by Lowary.
1-O-Acetyl-sugar 97 was converted into 1-C-allyl derivative 97a by classical reaction with
allyltrimethylsilane, and this derivative was ‘dimerized’ under the metathesis conditions with
Grubbs’ catalyst ( > Scheme 42) [89].
Unsaturated sugars are used also as starting materials for the preparation of complex natural
products and their analogs. For example, radical cyclization of 98 (readily prepared in well
defined steps from D-glucal) led to synthon 99, a precursor of antifungal agent GM222712
(a close analog of sordarin) [90]. The cascade reaction of 100 with the nucleophile catalyzed
with gold-III provided also the bicyclic skeleton with a different arrangement of unsaturated
bonds ( > Scheme 43) [91].
⊡ Scheme 42