Stereoselective alkylation of oxathiazinane N,O-ketals for the construction of AZA-quaternary carbon centers

Stereoselective construction of aza-quaternary carbon centers was achieved using the alkylation of oxathiazinane N,O-ketals prepared by Rh(II)-catalyzed C-H amination of sulfamates. The addition of alkyl Grignard reagents into N,O-ketals in the absence of any Lewis acid proceeded stereoselectively to provide the corresponding alkylated products with an aza-quaternary carbon center in high yields. The obtained product could be converted into an α-amino alcohol derivative, which is a potential synthetic intermediate for sphingofungin F and its derivatives.