584
3
Chemical Glycosylation Reactions
a variety of sugar alcohols to give β and α disaccharides 97 and 99, respectively, in moderate
to good yields ( > Scheme 13a,b) [65,66]. 2-Deoxy-2-N-tetrachlorophthaloyl NPGs, e. g. 100,
103, [67,68,69] are useful donors for the stereocontrolled access to 1,2-trans glycosides as
exemplified in > Scheme 13c,d. Good yields of disaccharide 102, and aminoacid 104 were
obtained by the use of NIS/TESOTf as promoter. β-N-Linked glycopeptide 106 was prepared
by treatment of 105 with acid 88 in dry MeCN containing NBS ( > Scheme 13e).
Controversial results have been reported when 2-deoxy-2-azido NPGs were used as glycosyl donors ( > Scheme 14). Fraser-Reid and co-workers reported that 107 failed to give
pseudo-disaccharide 109 upon reaction with acceptor 108 under the agency of NIS/TESOTf
⊡ Scheme 14
Glycoside formation from pent-4-enyl 2-deoxy-2-azido NPGs
3
Chemical Glycosylation Reactions
a variety of sugar alcohols to give β and α disaccharides 97 and 99, respectively, in moderate
to good yields ( > Scheme 13a,b) [65,66]. 2-Deoxy-2-N-tetrachlorophthaloyl NPGs, e. g. 100,
103, [67,68,69] are useful donors for the stereocontrolled access to 1,2-trans glycosides as
exemplified in > Scheme 13c,d. Good yields of disaccharide 102, and aminoacid 104 were
obtained by the use of NIS/TESOTf as promoter. β-N-Linked glycopeptide 106 was prepared
by treatment of 105 with acid 88 in dry MeCN containing NBS ( > Scheme 13e).
Controversial results have been reported when 2-deoxy-2-azido NPGs were used as glycosyl donors ( > Scheme 14). Fraser-Reid and co-workers reported that 107 failed to give
pseudo-disaccharide 109 upon reaction with acceptor 108 under the agency of NIS/TESOTf
⊡ Scheme 14
Glycoside formation from pent-4-enyl 2-deoxy-2-azido NPGs