Preparation and Improved Stability of N-Boc-α-amino-5-acyl Meldrum's Acids, a Versatile Class of Building Blocks for Combinatorial Chemistry

The preparation of novel N-Boc-α-amino-5-acyl Meldrum's acids is described. The synthetic inaccessibility and instability of several of these products have led to the development of a protocol that allows the synthesis of their corresponding 4-(dimethylamino)pyridine (DMAP) salts (5-AMA-DMAP's), which exhibit superior stability compared to that of the free 5-AMA. A simple and expedient ion-exchange method was developed for the quantitative removal of DMAP to liberate the synthetically useful DMAP-free form when needed.