A practical synthesis of L-valyl-pyrrolidine-(2R)-boronic acid:: Efficient recycling of the costly chiral auxiliary (+)-pinanediol

A practical synthesis Of L-valyl-pyrrolidine-(2R)-boronic acid (1) is detailed. A previously disclosed synthesis of 1 (Snow, R.; Kelly, T. R.; Adams, J.; Coutts, S.; Perry, C. (Boehringer Ingelheirn Pharmaceuticals, Inc.). WO 93/10127, 1993) was significantly improved by developing an efficient process for recycling the costly chiral auxiliary (+)- pinanediol.