Further Anomeric Esters
3.3
543
Furthermore, Mukaiyama et al. investigated the glycosylation with N-acetyl-α-neuraminosyl
acetate for the stereoselective synthesis of N-acetyl-α-neuraminosyl-galactose disaccharide by
using a variety of combinations of Lewis acids, for example, SiCl 4 , TiCl 4 , SnCl 4 , MeSiCl 3 ,
Me 2 SiCl 2 , or PhSiCl 3 , with AgClO 4 , in which the combination of Me 2 SiCl 2 and AgClO 4
proved to be the most suitable promoter system ( > Scheme 39) [48]. Kakinuma et al. applied
the SnCl 4 /AgClO 4 combination as the promoter to the glycosylation of an O-TMS-aglycone
with the appropriately protected 1-O-acetyl aminosugar for the total synthesis of Vicenistatin,
a novel 20-membered macrocyclic lactam antitumor antibiotic ( > Scheme 40) [49].
⊡ Scheme 40
(Ref. [49])
⊡ Scheme 41
(Ref. [50])
⊡ Scheme 42
(Ref. [51])
3.3
543
Furthermore, Mukaiyama et al. investigated the glycosylation with N-acetyl-α-neuraminosyl
acetate for the stereoselective synthesis of N-acetyl-α-neuraminosyl-galactose disaccharide by
using a variety of combinations of Lewis acids, for example, SiCl 4 , TiCl 4 , SnCl 4 , MeSiCl 3 ,
Me 2 SiCl 2 , or PhSiCl 3 , with AgClO 4 , in which the combination of Me 2 SiCl 2 and AgClO 4
proved to be the most suitable promoter system ( > Scheme 39) [48]. Kakinuma et al. applied
the SnCl 4 /AgClO 4 combination as the promoter to the glycosylation of an O-TMS-aglycone
with the appropriately protected 1-O-acetyl aminosugar for the total synthesis of Vicenistatin,
a novel 20-membered macrocyclic lactam antitumor antibiotic ( > Scheme 40) [49].
⊡ Scheme 40
(Ref. [49])
⊡ Scheme 41
(Ref. [50])
⊡ Scheme 42
(Ref. [51])