Resolution of limonene 1,2-epoxide diastereomers by mercury(II) ions

When HgCl2 was added to a diastereomeric mixture of cis- and trans-(4S)-lim onene 1,2-epoxide, the Hg(II) ions stereoselectively complexed to the cis e poxide, enabling ring opening by water. The resulting mercuric salt could b e demetalated by treatment with NaBH4, giving a mixture of diastereomeric ( 1S,2S,4S)- and (1R,2R,4S)-diols. The remaining trans-(4S)-epoxide was obtai ned in > 98% d.e. and 40% yield. For reactions on a larger scale, the most convenient reaction system was Hg(OAc)(2) in 50% acetone/tris-HCl buffer pH 7.0. The reaction rate was affected by the pH, with pH 6-8 as optimum. (C) 2001 Elsevier Science Ltd. All rights reserved.