Diffusion in heterogeneous polymer systems : a nuclear magnetic resonance study

Abstract

Both enantiomers of 1-(1,3-dithian-2-yl)-2-propanol (5) 1-(1,3-dithiolan-2-yl)-2-propanol (6), and halogenated derivatives of 5 was obtained by microbial reductions and lipase catalyzed esterifications. (2S)-1-(1,3-dithian-2-yl)-3-chloro-2-propanol and (2R)-(1,3-dithian-2-yl)-3-chloro-2-propanol were converted to both enantiomers of 2-(1,3-dithian-2-ylmethyl)oxirane.

3-(1,3-Dithiane-2-yl)-3-buten-2-one (3) was biologically transformed to (S)-3-(1,3-dithian-2-yl)-2butanone.

Efficient methods have been developed for lipase catalyzed kinetic resolution of series of 1-(2-thienyl-alkanoles using lipase B from Candida antartica. 1-(2-Thienyl)-ethanone (13) was reduced to (S)-1-(2-theinyl)-ethanol with fermenting cells and various cell-preparations of Geotrichum candidum.

Cyclohexyl 4-bromo-3hydroxybutanoate (24) and benzyl 4-bromo-3-hydroxybutanoate (25) was tested in lipase catalyzed kinetic resolutions with limited success.

Ethyl 3-oxobutanoate and halogenated derivatives (21-23) were reduced enantioselectively by Geotrichum candidum. This revealed that G.candidum seems to contain at least two dehydrogenases with opposite stereoselectivity.

(1E)-1-Phenylhexa-1,5-dien-3-ol (26) was resolved by transeterifications using lipase B from Candida antartica and vinyl acrylate. Seperation of the enantiomers by column chromatography, subsequent chemical esterification of the unreacted enantiomer and ring closing metathesis yielded both enantiomers of the biologcally active compound Goniothalamin.