Biotransformations of Mannich bases and propiophenones by Brazilian microorganisms and enzymatic resolution of phenylpropanols by lipase from Candida antarctica (Novozym 435)

Abstract

Mannich base derivatives 1–3 were biotransformed through tandem enzymatic reactions by using several microorganisms isolated from Brazilian biomes. The hydrochlorides 1 and 3 produced propiophenone 1a, α,β-unsatured ketone 2c and alcohol ( S)- 1b (yield 40%, e.e. 81%, Aspergillus terreus). The hydrochloride 2 underwent the Baeyer–Villiger oxidation producing exclusively para-methoxy-phenol by A. terreus and A. niger. The propiophenone 1a was reduced to their corresponding enantiomerically enriched phenylpropanol ( S)- 1b (yield 65%, e.e. 81%, A. terreus). The para-methoxy-propiophenone 2a afforded Baeyer–Villiger reaction hydrolyzed product, the para-methoxy-phenol (yield 80%, A. terreus). The racemic phenylpropanols 1b, 2b were resolved by lipase-catalyzed kinetic resolution (Novozym 435) affording ( S)-alcohols 1b, 2b and ( R)-acetates 1d, 2d in high enantiomeric excesses (up to 99%) and good yields (40–45%). We screened new microorganisms in biotransformation of Mannich bases, propiophenones and applied enzymatic resolution of phenylpropanols by Candida antarctica lipase.