N-Glycosylation with sulfoxide donors for the synthesis of peptidonucleosides.

The synthesis of glycopyranosyl nucleosides modified in the sugar moiety has been less frequently explored, notably because of the lack of a reliable method to glycosylate pyrimidine bases. Herein we report a solution in the context of the synthesis of peptidonucleosides. They were obtained after glycosylation of different pyrimidine nucleobases with glucopyranosyl donors carrying an azide group at the C4 position. A methodological study involving different anomeric leaving groups (acetate, phenylsulfoxide and ortho-hexynylbenzoate) showed that a sulfoxide donor in combination with trimethylsilyl triflate as the promoter led to the best yields.

Synthesis of enantioenriched 1,2-trans-diamines using the borono-Mannich reaction with N-protected α-amino aldehydes.

The three-component Petasis borono-Mannich reaction starting with easily accessible N-protected α-amino aldehydes produces efficiently and diastereoselectively 1,2-trans-diamines with an enantiomeric excess of up to 98%.