Enzymatic resolution of α,α-disubstituted α-amino acid esters and amides
摘要:
The scope and limitations of the enzymatic resolution of alpha,alpha-disubstituted alpha-amino acid amides by an amino acid amidase from Mycobacterium neoaurum and of the corresponding ethyl esters with Pig liver esterase (PLE) have been studied. Moderate enantiomeric excesses were obtained with PLE, with only a narrow substrate specificity. Mycobacterium neoaurum on the contrary yields a broad range of S-alpha,alpha-disubstituted alpha-amino acids 1 and the corresponding R-amides 2.
Enantiopure Cα-tetrasubstituted α-amino acids. Chemo-enzymatic synthesis and application to turn-forming peptides
摘要:
By a chemo-enzymatic approach we carried out a large-scale synthesis of four enantiopure, sterically constrained, C-alpha-tetra-substituted alpha -amino acids, all characterized by a sidechain (CCdelta)-C-gamma double bond. By using one of them (L-Mag), we prepared an N-alpha-protected tetrapeptide benzylamide which was shown to adopt a beta -turn conformation and to efficiently undergo ring-closing olefin metathesis. (C) 2001 Elsevier Science Led. All rights reserved.