Efficient access to 2,5-substituted tetrahydrofurans via a one-pot cyclization of di- and triepoxides

Production of Enantiopure Chiral Epoxides with E. coli Expressing Styrene Monooxygenase

Styrene monooxygenases are a group of highly selective enzymes able to catalyse the epoxidation of alkenes to corresponding chiral epoxides in excellent enantiopurity. Chiral compounds containing oxirane ring or products of their hydrolysis represent key building blocks and precursors in organic synthesis in the pharmaceutical industry, and many of them are produced on an industrial scale. Two-component recombinant styrene monooxygenase (SMO) from Marinobacterium litorale was expressed as a fused protein (StyAL2StyB) in Escherichia coli BL21(DE3). By high cell density fermentation, 35 g_DCW/L of biomass with overexpressed SMO was produced. SMO exhibited excellent stability, broad substrate specificity, and enantioselectivity, as it remained active for months and converted a group of alkenes to corresponding chiral epoxides in high enantiomeric excess (˃95–99% ee). Optically pure (S)-4-chlorostyrene oxide, (S)-allylbenzene oxide, (2R,5R)-1,2:5,6-diepoxyhexane, 2-(3-bromopropyl)oxirane, and (S)-4-(oxiran-2-yl)butan-1-ol were prepared by whole-cell SMO.

Formation of tetrahydrofurans via a 5-endo-tet cyclization of aziridines--synthesis of (-)-pachastrissamine

The formation of tetrahydrofurans from 2-hydroxyalkyl-oxirane or aziridine is reported. The 5-endo-tet cyclization/ring opening of aziridine proceeded smoothly to give tetrahydrofurans (THFs) under mild conditions. In contrast, the corresponding process of oxirane was unsuccessful and a sequence of SN2 substitution/cyclization was required to form THFs. The application of the process to prepare ent-(-)-pachastrissamine is described.