Hemisynthesis of new labdane derivatives from (-)-sclareol.

A straightforward and very simple access to different analogues of (+)-subersic acid 7, the unnatural enantiomer (compounds 12) from naturally occurring (-)-sclareol 1 is described. We also report new conditions for the preparation of keto-intermediate 8 using maleic acid and describe hemiketal 11 as the new intermediate of degradative oxidation of 1.