Introduction

Abstract

New methods for the construction of condensed five-membered ring systems continue to be developed at an accelerated pace. The challenges underlying this tremendous current upsurge of interest arise from several directions. One stems from the desire to elucidate and resolve those special problems associated with the incorporation of added strain not present when six-membered rings are mutually fused. The many structurally interesting polyquinane natural products isolated and characterized in recent years have provided a particularly delightful forum for application of various new synthetic protocols, many of which must equally well accommodate the particular stereochemical demands of each individual target. Synthetic elaboration of a marvellous array of new unnatural molecules also holds continued fascination.