Efficient Pathways to Precursors of Pyrrolidine Azasugar Structures.

Hydroxy-substituted pyrrolidines are important structural elements in azasugars. Effective precursors for such compounds are pyrrolo-oxazolidinones of type 1. Short asymmetric syntheses starting from easily available low-priced precursors are desirable. Two efficient pathways to these structures starting from the 4-methoxylated oxazolidinones 2 and 3, easily accessible from the chiral pool, have been successfully developed. These oxazolidinones can be used as amidoalkylation reagents. Via Sakurai reactions and subsequent intramolecular cyclization, the synthesis of bicyclic pyrrolidines is possible in a stereocontrolled way.