Highly Stereoselective Syntheses of Proline-Derived Vicinal Amino Alcohols through Grignard Addition onto N-Tosylprolinal

A highly diastereoselective Grignard addition to N-tosyl-l-prolinal has been developed to deliver a variety of proline-derived vicinal amino alcohols in good to excellent yields with high diastereoselectivities. A similar selectivity was also obtained by using N-tosyl-d-prolinal. The methodology has been applied to the synthesis of medicinally important 3-hydroxy-2-phenylpiperidines.