Enzymatic preparation and absolute configuration of (+)-2-(hydroxymethyl)cyclohexanone

Lipase mediated treatment of racemic 2-(hydroxymethyl)cyclohexanone, (+/-)-1, with vinyl acetate allows enantioselective acetylation to give the acetate (R)-(+)-4 and unreacted (S)-(+)-1 in satisfactory yield and enantiomeric purity. The absolute configuration of (S)-(+)-1 (and therefore that of (R)-(+)-4 as well) was determined by the analysis of the n-->pi* Cotton effect at 290 nm present in the CD spectrum of (S)-(+)-1 by means of the octant rule and CNDO/S calculations. Furthermore the optical rotatory power of optically pure (S)-(+)-1 and (R)-(+)-4 have been determined

HIGH DIASTEREO-SELECTIVITY AND ENANTIOSELECTIVITY IN THE ENZYMATIC-HYDROLYSIS OF A RACEMIC ANHYDRODEOXYSUGAR - A TOTALLY SYNTHETIC APPROACH TO BOTH ENANTIOMERS OF BOIVINOSE

The microsomal epoxide hydrolase-promoted hydrolysis of racemic isobutyl 3,4-anhydro-2,6-dideoxy-β-lyxohexopyranoside, which is easily prepared from isobutyl vinyl ether and but-3-en-2-one, occurs with very high regio-and enantio-selectivity, with kinetic resolution leading to the L-and D-forms of isobutyl β-boivinoside, both with an enantiomeric excess of at least 96%

Efficient differentiation of the hydroxyl groups of 3,4-O-isopropylidene-D-galactopyranosides by lipase catalyzed esterification and de-esterification

The Pseudomonas sp. (LPS) promoted acyl transfer from vinyl acetate to selected 3,4-O-isopropylidene-D-galactopyranosides takes place in a completely selective manner giving in high yield the corresponding 6-O-acetates. The acetylation rate is strongly dependent on the type and the orientation of the aglycon, varying from a maximum of reactivity for the 1-deoxy derivative, 1,5-anhydro-3,4-O-isopropylidene-D-galactitol (1d), to a minimum for beta configurated alkyl glycosides and showing a complete loss of reactivity for 3',4':2,3:5,6-tri-O-isopropylidenelactose dimethyl acetal (1e). The latter compound is, however, selectively 6'-O-esterified in good yield by lipase from Candida Antarctica and vinyl acetate. Also the course of the enzymatic hydrolysis of 2,6-di-O-acetyl-3,4-O-isopropylidene-D-galactopyranosides 2 is dependent on the type of the aglycon, both for the reaction rate and the selectivity. The 2-O-acetates 4 are selectively obtained in good yields with porcine pancreatic lipase (PPL) promoted hydrolysis in the case of beta- and alpha-methyl, and 1-deoxy derivatives (2a, 2b and 2d), while for beta-benzyl (2c) and lactose (2e) analogues satisfactory results are obtained with lipase from Mucor miehei (IM20)

A SIMPLE STEREOSPECIFIC ROUTE TO 5-C-ALKOXY-D-GALACTOPYRANOSIDES AND TO L-ARABINO-HEXOS-5-ULOSES

5-C-alkoxy-beta-D-galactopyranosides, which are easily convertible into L-arabino-hexos-5-uloses, can be prepared from beta-D-galactopyranosides via peroxyacid oxidation in an alcoholic solvent of intermediate 4-deoxy-alpha-L-threo-hex-4-enopyranoside

NEW SYNTHETIC PATHWAYS TO 5-C-ALKOXYPYRANOSIDES AND TO HEXOS-5-ULOSE DERIVATIVES

Several new 5-C-alkoxy-D-galactopyranosides, e.g., I, (R=PhCH2, Me) have been obtained by oxidn. of 4-deoxy-alfa-L-threo-hex-4-enopyranosides, e.g., II (easily available from beta-D-galactopyranosides), with 3-ClC6H4CO3H in alc. solvents. They have been converted into the so far unreported L-arabino-hexos-5-ulose and some of its derivs. through hydrolytic and hydrogenolytic steps. Tautomeric equil. for these keto aldoses have been investigated by NMR technique