Stereocontrolled synthesis of ara-type cyclohexenyl nucleosides.

A highly stereocontrolled synthesis of a new class of carbocyclic nucleosides, ara-type cyclohexenyl nucleosides, was developed. The key intermediate (+/-)-9 was obtained after a series of transformations starting from easily available endo-bicyclo carboxylic acid (+/-)-3. The allylic hydroxyl group of (+/-)-9 was masked via oxidation with manganese dioxide and released, after protection of the 2'-hydroxyl group, via reduction with NaBH(4) in the presence of CeCl(3).7H(2)O. The base moiety was introduced with use of the Mitsunobu methodology.