Chemoenzymatic Synthesis of Vitamin B5-Intermediate
(<i>R</i>)‑Pantolactone via Combined Asymmetric Organo-
and Biocatalysis
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Abstract
The combination of an asymmetric
organocatalytic aldol reaction
with a subsequent biotransformation toward a “one-pot-like”
process for the synthesis of (<i>R</i>)-pantolactone, which
to date is industrially produced by a resolution process, is demonstrated.
This process consists of an initial aldol reaction catalyzed by readily
available l-histidine followed by biotransformation of the
aldol adduct by an alcohol dehydrogenase without the need for intermediate
isolation. Employing the industrially attractive starting material
isobutanal, a chemoenzymatic three-step process without intermediate
purification is established allowing the synthesis of (<i>R</i>)-pantolactone in an overall yield of 55% (three steps) and high
enantiomeric excess of 95%