exo-glycal approaches to C-linked glycosyl amino acid synthesis

Two novel routes to C-linked glycosyl amino acids are described; the first involves elaboration of an exo-glycal and subsequent Ramberg-Backlund rearr angement of a sulfone intermediate to give, after functional group manipula tion, a protected C-glycosyl serine, while the second uses hydroboration-Su zuki coupling of the same exo-glycal to produce ultimately the correspondin g C-glycosyl asparagine analogue.