Chemical and Enzymatic Synthesis of Dehydropeptides and Their Fluoro Analogs

Abstract

Fluorine-substituted dehydroalanine can lead to irreversible linkages of nucleophile to dehydroalanines by an addition elimination mechanism and can be applied to the design of enzyme inhibitors and active site affinity labels. Fluorodehydroalanine has been synthesized from serine in 7 steps with a fluoro-Pummerer rearrangement as the key step. The stereochemical integrity at the alpha-carbon in the fluoro-Pummerer rearrangement was investigated and proven to be retained. Furthermore, dehydropeptides and their fluoro analogs were prepared in an enzymatic fashion. For instance, fluorinated dipeptides, L-alanine-D-fluoroalanine and L-alanine- D,L-difluoroalanine were treated with the epimerase YcjG to produce L-Ala-Dha and L-Ala-Dha(F), respectively, as determined by 1H NMR, 19F NMR and MS (ESI).