An asymmetric synthesis of enantiopure chair and twist trans-cyclooctene isomers

A pair of enantiopure chair and twist trans-cyclooctenes isomers were prepared by regioselective Sharpless asymmetric dihydroxylation of the central olefin of (E)-1,5,9-dectriene triene, with subsequent ring-closing metathesis to form an enantiomerically pure cis-cyclooctene. Epoxidation and ring-opening with lithium diphenylphosphide gives after oxidation two diastereomeric hydroxyphosphine oxides. Separate syn-elimination of these diastereomers gives enantiomerically pure chair and twist trans-cyclooctenes. A discussion of the molecular motion required to achieve the chair and twist isomers is discussed with reference to the X-ray crystal structure obtained for the hydroxyphosphine oxide leading to the chair trans-cyclooctene. (C) 2004 Elsevier Ltd. All rights reserved.