Synthesis of enantiopure (αMe)Dip and other α-methylated β-branched amino acid derivatives
摘要:
This report describes the synthesis of the two enantiomerically pure a-methylated P-branched phenylalanine derivatives, (S)- and (R)-alpha-methyl-beta,beta-diphenylalanine-(alphaMe)Dip-starting from the chiral building blocks (R)- and (S)-N-Boc-N,O-isopropylidene-alpha-methylserine methyl esters, respectively. The key step involves a double alkylation with a Grignard reagent on an ester group. The use of the same protocol for the preparation of other alpha-methylated beta-branched serine derivatives is also described. (C) 2003 Elsevier Science Ltd. All rights reserved.