A NEW ASYMMETRIC APPROACH TOWARDS 2-PYRROLIDINONES AND PYRROLIDINES -SIMPLE VERSUS DOUBLE STEREODIFFERENTIATION

The condensation of a chiral 2-silyloxypyrrole derivative with achiral and chiral formyl cation equivalents has been studied for the first t ime. The methodology allows to build-up pyroglutammic aldehydes and pr olinal systems with a stereocontrol from good to excellent. Whereas th e chiral auxiliary residing on the pyrrole system shows an intrinsic g ood level of diastereoface discrimination at C-5, the combined use of a 2-methoxy-3-tosyl-oxazolidine as a chiral formylating agent allows a total stereocontrol of the condensation. A rationale for the observed stereochemical outcome is presented.