A concise C-glycosyl amino acid synthesis by alkenyl C-glycoside-vinyloxazolidine cross-metathesis.: Synthesis of glycosyl serine, asparagine and hydroxynorvaline isosteres

A convergent synthesis has been developed to afford C-linked glycosyl amino acids by cross-metathesis of vinyl, allyl, and butenyl C-glycosides with N-Boc-vinyloxazolidine using the Grubbs 1,3-dimesityl-4,5-dihydroimidazol-2-ylideneruthenium carbene. the method has been employed to introduce through an alpha -linkage, an alpha -aminopentanoic acid chain,at the anomeric carbon of beta -D-C-gentiobiose to give a totally artificial glycosyl alpha -amino acid of a disaccharide. This compound represents the isostere of the alpha -linked glycosylasparagine moiety of the natural glycopeptide nephritogeno side.