Among the common alpha -amino acids, proline is useful as a chiral source in asymmetric synthesis. Many methods including asymmetric synthesis of proline has been reported [1]. However, development of a new and convenient method for preparation of optically active proline derivatives is still required. We now report that treatment of L-or D-N-protected 2-amino-5-bromopentanoic acid ester (1), which was prepared from protected glutamic acid, with sodium hydride gave the corresponding L- or D-proline derivative (2) in high yield respectively (Scheme 1).
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