Giancarlo Fantin

Anti-Prelog microbial reduction of prochiral carbonyl compounds

Abstract Yarrowia lipolytica strains isolated from various habitats were tested in the reduction of prochiral carbonyl groups. The anti-Prelog reduction ( R -enantiomer) is observed with different yields and enantiomeric excesses depending on the structure of the ketones 1a-e .

Thiazolylmethylenetriphenylphosporane and its benzo derivative: stable and practical wittig reagents for the synthesis of vinylthiazoles and vinylbenzo : two-carbon homologation of aldehydes

Abstract The title thiazolyl phosphorane is a stable yet quite reactive Wittig-type reagent which upon reaction with various aldehydes affords vinylthiazoles, mainly or exclusively as E -isomers, in very good yields. Also the benzothiazolyl phosphorane derivative, unlike a literature report, prove to react with aldehydes. Vinylthiazoles subjected to formyl deblocking from thiazole nucleous afford two-carbon homologated satured aldehydes. As an example, one of these vinylthiazoles, viz. the β-phenyl derivative 8f, proves to add n -butyl lithium cuprate to give after the formyl deblocking 3-phenylheptanal.

Plants in organic synthesis: an alternative to baker's yeast

The reduction of acetophenone 1 and the hydrolysis of 1-acetoxy-2-methylcyclohexene 3 with various commercially available plants to the corresponding S-carbinol 2 and S-ketone 4 are described. The further incubation of 2-methylcyclohexanone 4 with some plants affords the enantiomerically pure trans- and/or cis-alcohol 5 and 6, respectively.

Combined microbial oxidation and reduction: a new approach to the highyield synthesis of homochiral unsaturated secondary alcohols from racemates

Abstract The oxidation of racemic secondary alcohols with Bacillus stearothermophilus followed by reduction of the mixture with Yarrowialipolytica to afford high yields of the enantiomerically pure R-alcohols 1a, b, d is described. Comparisons with Yarrowia lipolytica reduction, Bacillus stearothermophilus oxidation, and the contemporary use of the two microrganisms have been made.

Kinetic resolution of racemic secondary alcohols via oxidation with Yarrowia lipolytica strains

Abstract Cyclic and alicyclic racemic secondary alcohols are kinetically resolved via oxidation with Yarrowia lipolytica strains. The comparison of the oxidation reactions with the reductions of the corresponding ketones supports the hypothesis of the presence of two alcohol dehydrogenases with opposite enantioselectivity.

Stereospecific homologation of d-xylo and d-galacto dialdoses by 2-trimethylsilylthiazole

Abstract Homologation of the title dialdoses is carried out by diastereogenic addition of 2-trimethylsilylthiazole (1) to the side-chain aldehyde and unmasking the formyl group from thiazole ring; further addition of 1 to the resulting homologated dialdoses exhibited good levels of diastereoselectivity.

Asymmetric epoxidation of cinnamic acid derivatives using dioxiranes generated in situ from dehydrocholic acid

Abstract The asymmetric epoxidation of different cinnamic acid derivatives in water–NaHCO 3 has been achieved using dehydrocholic acid as the optically active ketone and Oxone® as the oxygen source (with product e.e. values of up to 75%).

Xanthomonas maltophilia CBS 897.97 as a source of new 7β- and 7α-hydroxysteroid dehydrogenases and cholylglycine hydrolase: Improved biotransformations of bile acids

The paper reports the partial purification and characterization of the 7beta- and 7alpha-hydroxysteroid dehydrogenases (HSDH) and cholylglycine hydrolase (CGH), isolated from Xanthomonas maltophilia CBS 897.97. The activity of 7beta-HSDH and 7alpha-HSDH in the reduction of the 7-keto bile acids is determined. The affinity of 7beta-HSDH for bile acids is confirmed by the reduction, on analytical scale, to the corresponding 7beta-OH derivatives. A crude mixture of 7alpha- and 7beta-HSDH, in soluble or immobilized form, is employed in the synthesis, on preparative scale, of ursocholic and ursodeoxycholic acids starting from the corresponding 7alpha-derivatives. On the other hand, a partially purified 7beta-HSDH in a double enzyme system, where the couple formate/formate dehydrogenase allows the cofactor recycle, affords 6alpha-fluoro-3alpha, 7beta-dihydroxy-5beta-cholan-24-oic acid (6-FUDCA) by reduction of the corresponding 7-keto derivative. This compound is not obtainable by microbiological route. The efficient and mild hydrolysis of glycinates and taurinates of bile acids with CGH is also reported. Very promising results are also obtained with bile acid containing raw materials.

Kinetic resolution of vic-diols by Bacillus stearothermophilus diacetyl reductase

Abstract The kinetic resolution of several racemic syn- and anti-1,2-diols by enzymatic oxidation with Bacillus stearothermophilus diacetyl reductase is described. The enantiomerically pure (R,R)- and (R,S)-diols are recovered in almost quantitative yield.

Microbial oxidation with Bacillus stearothermophilus : high enantioselective resolution of 1-heteroaryl and 1-aryl alcohols

Abstract The enantioselective resolution of the racemic 1-heteroaryl- and 1-arylethanols 1a-h via microbial oxidation with Bacillus stearothermophilus to give the R -enantiomers with high enantiomeric excesses is described. The kinetic resolution of 1-(2-thienyl)ethanol 1b by oxidation with Acinetobacter calcoaceticus anitrat to S -enantiomer (ee 100%) is also reported.