The α,α-difluoro-β-hydroxyketone skeleton is an important pharmacodynamic structure in the synthesis study of pharmaceuticals. Herein, we describe a novel iron mediated Reformatsky reaction of iododifluoroacetophenones with aldehydes, which offers a relatively more economical and environment friendly route for the construction of α,α-difluoro-β‑hydroxyl ketone with good yield. In addition, iron shows
The bioreduction of alpha,alpha-difluorinated ketones, ethyl 2,2-difluoro-3-oxobutanoate (2a) and 2,2-difluoro-1-phenyl-1,3-butanedione (2b), with cells of recombinant Escherichia coli overproducing SCR (Saccharomyces cerevisiae carbonyl reductase from bakers' yeast) and GDH (glucose dehydrogenase from Bacillus megaterium) gave enantiomerically pure alcohols, ethyl (S)-2,2-difluoro-3-hydroxybutanoate ((S)-1a) and (S)-2,2-difluoro-3-hydroxy-1-phenyl-1-butanone ((S)-1b), respectively, in the presence of NADP(+) and glucose in buffer. The reductions of 2a and 2b proceeded completely at the substrate concentrations of 0.4 M (67 g/L) and 1.0 M (200 g/L), respectively. The opposite enantiomers (R)-1a and (R)-1b were also produced by enzyme E039 (a mixture of carbonyl reductase and formate dehydrogenase) contained in Chiralscreen OH (Daicel Chemical Industries) in the presence of NADH and sodium formate in buffer. Enantiomerically pure (S)-1a was converted by organic synthetic methods into an a,a-difluorinated derivative of (R)-beta-aminobutyric acid (BABA) in three steps. (C) 2010 Elsevier B.V. All rights reserved.
TSUKAMOTO, TAKASHI;YAMAZAKI, TAKASHI;KITAZUME, TOMOYA, SYNTH. COMMUN., 20,(1990) N0, C. 3181-3186