Total synthesis of bleomycin A(sub 2) and related agents. 4. Synthesis of the disaccharide subunit: 2-O-(3-O-carbamoyl-alpha-D-mannopyranosyl)-L-gulopyranose and completion of the total synthesis of bleomycin A(sub 2)

The total synthesis of bleomycin A (sub 2) involves the incorporation of the disaccharide subunit 2-O-(3-O-carbamoyl-alpha-D-mannopyranosyl)- L-gulopyranose into the procedure. A diasteroselective alpha-O-glycosidation is the vital step for the synthesis of the disaccharide. Order of assemblage of subunits is critical for the total synthesis of bleomycin A(sub 2).