Access to ring-expanded analogues of 2-amino sugars.

Ring-expanded 2-N-acetylamino sugar analogs of D-glucose, D-galactose, and D-mannose have been prepared by a new synthetic route. Aspects of the highly substituted alpha-amino aldehyde intermediates made them central to the approach. First, they were accessed via diastereoselective addition of a vinyl Grignard onto protected glycosyl amines. Also, the sterics of the bis-protected amine favored the formation of only one glycoside anomer. The new analogues reported here should prove useful in the development of tools to investigate the role of 2-amino sugars in biology.