Synthesis of aza-analogues of the glycosylated tyrosine portion of mannopeptimycin-E.

Two C4' amido disaccharide analogues of mannopeptimycin-E were synthesized via an iterative palladium glycosylation sequence. The stereoselective synthesis of the C4' acylated 1,4-alpha,alpha-manno,manno-amido disaccharide has been achieved in ten steps from a protected d-tyrosine. The path relies upon a regio- and diastereoselective palladium-catalyzed azide substitution reaction. The competence of the synthesis is demonstrated by the good overall yield (21%) from protected tyrosine.