An acid catalysed rearrangement was employed for the enantiospecific conversion of isotwistanol to tricyclo[5.2.1.04,8]decanes, which provided support for the proposed biosynthesis of allopupukeananes from pupukeananes. The strategy has been further extended to the enantiospecific synthesis of a homobrexane. © 2005 Elsevier Ltd. All rights reserved.