O-Glycosyl Donors
3.4
639
5.5 2 -(Allyloxycarbonyl)benzyl (ACB) Glycosides: New “Latent” Donor
for the Preparation of “Active” 2-Azido-2-deoxy BC Glycosyl Donors
Kim and co-workers introduced 2 -(allyloxycarbonyl)benzyl (ACB) glycosides, e. g. 426a,
as new “latent” glycosyl donors for 2-azido-2-deoxy-glucosides [212]. Introduction of the
new ACB group in the place of the previously used BCB group was necessary because the
azide functionality at C-2 was also reduced during the conversion of the BCB group into the
CB group under the normally used hydrogenolysis conditions (Pd/C, H 2 , NH 4 OAc, MeOH).
2-Azido-2-deoxy ACB glycosides could be converted into active CB glycosyl donors (e. g.
426b, > Scheme 68) without affecting the azide functionality on treatment with a catalytic
amount of Pd(Ph 3 P) 4 in the presence of morpholine [213].
⊡ Scheme 68
2 (Allyloxycarbonyl)benzyl (ACB) glycosides
⊡ Scheme 69
Synthesis of trisaccharide 431