492
3
Chemical Glycosylation Reactions
ing no other functional side chains (!), leading to direct reaction in the order Tyr > Ser > Thr,
as shown in > Scheme 25 [161]. The peptide was linked via a photolabile linker (PLL) to the
resin (→ 25a). Galactosylation with 25b (→ 25c), then O-deprotection (→ 25d), and galactosylation with 25b gave 25e; threonine did not undergo reaction in this case.
A particularly interesting case is the glycosylation of the vancomycin aglycone to achieve
the vancomycin total synthesis as successfully investigated by the Nicolaou group [162,163].
They obtained very good results on glycosylation of aglycone 26a with glycosyl donors 26b
and 26g affording intermediates 26c and 26g ( > Scheme 26), which were further transformed,
thus furnishing via 26d target molecule 26e. Similarly, vancomycin analogs were prepared by
⊡ Scheme 27
3
Chemical Glycosylation Reactions
ing no other functional side chains (!), leading to direct reaction in the order Tyr > Ser > Thr,
as shown in > Scheme 25 [161]. The peptide was linked via a photolabile linker (PLL) to the
resin (→ 25a). Galactosylation with 25b (→ 25c), then O-deprotection (→ 25d), and galactosylation with 25b gave 25e; threonine did not undergo reaction in this case.
A particularly interesting case is the glycosylation of the vancomycin aglycone to achieve
the vancomycin total synthesis as successfully investigated by the Nicolaou group [162,163].
They obtained very good results on glycosylation of aglycone 26a with glycosyl donors 26b
and 26g affording intermediates 26c and 26g ( > Scheme 26), which were further transformed,
thus furnishing via 26d target molecule 26e. Similarly, vancomycin analogs were prepared by
⊡ Scheme 27