It has been demonstrated for the first time that Rh(I)-catalyzed asymmetric hydrogenation of cyclic β-enamino acid derivatives 1 using chiral bisphosphines could be a highly efficient synthetic method for optically active homoproline derivatives. The enantioselectivity and conversion yield were largely dependent upon the chiral ligand. Using the Me-BDPMI forming a seven-membered metal chelate, the N-acetylated β-enamino acid methyl ester 1a was hydrogenated to give optically active homoproline derivative 2a with 100% conversion and 96% ee.
Bibliographical noteFunding Information:
This work was supported by a Korea National Center for Cleaner Production, a National Research Laboratory Program from MOST, a Center for Molecular Design and Synthesis at KAIST and a KIST. We would also like to thank Professor K. M. Kim for X-ray analysis and Leadgene Co. Ltd who generously supplied the cyclic β-enamino acid derivatives.