Unequivocal Synthesis of (<i>Z</i>)-Alkene and (<i>E</i>)-Fluoroalkene Dipeptide Isosteres To Probe Structural Requirements of the Peptide Transporter PEPT1

Abstract

[reaction: see text] Described is a novel synthetic route for dipeptide isosteres containing (Z)-alkene and (E)-fluoroalkene units as cis-amide bond equivalents via organocopper-mediated reduction of gamma-acetoxy- or gamma,gamma-difluoro-alpha,beta-unsaturated-delta-lactams. The synthesized isosteres were evaluated in terms of their affinities for the peptide transporter PEPT1. trans-Amide isosteres tended to possess higher affinities for PEPT1 as compared to the corresponding cis-amide bond equivalents.