STEREOCHEMICAL ASPECTS OF CYTOSOLIC EPOXIDE HYDROLASE HYDRATION OF METHYL DIEPOXYSTEARATES

Hydration of methyl diepoxystearate (2) al high cytosolic epoxide hydrolase (CEH) concentration produces the corresponding tetraol, while al physiological CEH concentration four tetrahydrofuran diol products (3-6) are produced. These same four products are obtained in the acid-catalyzed hydration of 2. Spectroscopic studies, primarily EI mass spectrometry and difference spectrum NOE, are reported which establish the regio- and stereoselectivity of 2 --> 3-6 (MS differentiating 3/4 from 5/6 and NOE differentiating 315 from 4/6). The observed syn arrangement of the two adjacent groups (i.e., substituents at C2 and C3) in the four THF-diols can only arise from an A2 type opening of the first epoxide. The resulting epoxydiol intermediate then cyclizes by A2 opening of the second cis-epoxide as established by synthesis of these hypothetical epoxydiol intermediates and their subsequent conversion to THF-diols 3-6.