Exploiting π-shielding interactions: a highly selective chiral auxiliary derived from a biogenic building block

A chiral auxiliary template, designed on the basis of π-shielding capability has been prepared from readily available L-proline. Cycloaddition to an acrylate derivative gave high endo preference, and diastereoselectivity as high as 99% was attainable. The electronic factors contributing to selectivity were probed, and the technology successfully applied to a polymer supported variant.