Efficient synthesis of β-halogeno protected l-alanines and their β-phosphonium derivatives

Stereoselective synthesis of unsaturated and functionalized L-NHBoc amino acids, using Wittig reaction under mild phase-transfer conditions

The stereoselective synthesis of a new amino acid phosphonium salt was described by quaternization of melting triphenylphosphine with the γ-iodo NHBoc-amino ester, derived from L-aspartic acid. The deprotection of the carboxylic acid function to afford the phosphonium salt with a free carboxylic acid group was achieved by a palladium-catalyzed desallylation reaction. This phosphonium salt was used in the Wittig reaction with aromatic or aliphatic aldehydes and trifluoroacetophenone, under solid-liquid phase-transfer conditions in chlorobenzene and in the presence of K(3)PO(4) as weak base, to afford the corresponding unsaturated amino acids without racemization. Thus, the reaction with substituted aldehydes allows to graft various functionalized groups on the lateral chain of the amino acid, such as trifluoromethyl, cyano, nitro, ferrocenyl, boronato, or azido. In addition, the reaction of the amino acid Wittig reagent with α,β-unsaturated aldehydes leads to amino acids bearing a diene on the lateral chain. Finally, this amino acid phosphonium salt appears to be a new powerful tool for the preparation of unsaturated and non-proteinogenic α-amino acids, directly usable for the synthesis of customized peptides.

A highly efficient route to enantiomerically pure l-N-Bz-Pmp(t-Bu)2-OH and incorporation into a peptide-based protein tyrosine phosphatase inhibitor

Phosphonomethyl phenylalanine (Pmp), a nonhydrolyzable mimic of phosphotyrosine, is an important building block in the development of peptide-based PTP inhibitors. We have designed a novel, efficient synthesis of N-Bz-Pmp(t-Bu)2-OH. A Pmp-containing peptide based on a known biological substrate of the tyrosine phosphatase CD45 (Ac-TEGQ-Pmp-QPQP-NH2) inhibits CD45 with an IC50 value of approximately 100 microM with virtually no inhibition of TCPTP up to concentrations of 120 microM.

Taking control of P1, P1' and double bond stereochemistry in the synthesis of Phe-Phe (E)-alkene amide isostere dipeptidomimetics

A protocol for the stereocontrolled independent preparation of both C-2 epimers of Phe-Phe trans-vinyl amide isostere dipeptidomimetics has been devised based on a Wittig-type reaction, in which two chiral building blocks were joined with excellent E-selectivity to give compounds of the type PhePsi[(E)-CH[double bond, length as m-dash]CH]-PheOH.