Abstract
Labdane diterpenoids have a bicyclic framework illustrated in the basic skeleton below and are the most common diterpenoids, which are widely distributed in terrestrial as well as marine organisms. Recent progress on the isolation of labdane diterpenoids are compiled in the review by Hanson.1 Biogenetically, cyclization of geranylgeranylpyrophosphate provides the bicyclic framework of labdane diterpenoids. In contrast to other diterpenoids, there is less structural diversity in labdane diterpenoids. In most of these compounds, the relative stereochemistry of the ring junctures is trans. With regard to the absolute stereochemistry, there are two enantio-series. Some of these compounds exhibit a wide range of biological properties2 such as anti-mutagenic,2c anti-bacterial and anti-fungal,2d cytotoxic,2e anti-inflammatory and analgesic activities,2g etc. In view of such interesting biological activities of labdane diterpenoids, many synthetic studies have been reported so far and still much efforts are being devoted to develop more efficient, stereo-controlled and general synthetic approaches. This article covers recent progress in the synthetic studies of labdane diterpenoids from 1996 to present.