Regio- and stereochemistry of the acid catalyzed and of a highly enantioselective enzymatic hydrolysis of some epoxytetrahydrofurans

• Published in: Tetrahedron Vol. 49; no. 28; pp. 6263 - 6276
• Main Authors: Barili, Pier Luigi, Berti, Giancarlo, Mastrorilli, Ettore
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.1993; Elsevier
• Subjects: Bioconversions. Hemisynthesis; Biological and medical sciences; Biotechnology; Chemistry; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Heterocyclic compounds; Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives; Methods. Procedures. Technologies; Organic chemistry; Preparations and properties; Hydrolysis; Enantioselectivity; Model compound; Epoxide; Chiral compound; Acid catalysis; Oxygen heterocycle; Glycol; Enzymatic reaction
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(01)87964-3

3,4-Epoxytetrahydrofuran is hydrolyzed by rabbit liver microsomal epoxide hydrolase (MEH) with a high preference for the attack by water at the ( S) epoxide carbon to give the ( R,R)-diol with an e.e. of 96.5±0.3%. In the acid catalyzed hydrolysis of trans-3,3a-epoxyoctahydrobenzofuran the oxirane ring is opened with inversion exclusively on the tertiary carbon atom to give the corresponding trans-diol, whereas hydrolysis of the cis isomer is less regioselective, the ratio of attack at the tertiary and secondary carbons being 81:19. The MEH catalyzed hydrolysis of the same two substrates occurs exclusively at their secondary epoxide carbons and with a very high enantioselectivity: only enantiomers of configuration (3 S,3a R) of the cis- and trans-epoxide are substrates for the enzyme and give the corresponding (3 R,3a R)-diols with at least 98% e.e., the corresponding (3 R,3a S)-epoxides being totally resistant to enzymatic hydrolysis. These results agree well with previously formulated rules on steric requirements of MEH subtrates. Absolute configurations and optical purities of new chiral compounds were obtained by chiroptical, NMR and chiral chromatographic techniques. Conformations of the octahydrobenzofuran derivatives were derived from coupling constants and found to be in fairly good agreement with those deduced from molecular mechanics calculations. Highly enantioselective hydrolyses with microsomal epoxide hydrolase (MEH). Opposite regioselectivity in acid catalyzed hydrolyses