Improvement of the chemoenzymatic synthesis of both enantiomers of keto-protected 4-amino-2-pentanone

An improved enantioselective synthesis (five steps, 37-44% yield versus sev en to 10 steps, 13.5 and 12% yield, respectively) of both enantiomers of ke to-protected 4-amino-2-pentanone has been realized, the key step being the microbiological reduction of 2,4-pentanedione. This study shows that microb iological reductions of the mono acetal-protected 2,4-pentanedione afforded in most cases the corresponding ketol with moderate to excellent enantiome ric excesses, depending on the microorganism used. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.