Synthetic studies to highly functionalised B ring labdanes

Several 6,7-dioxygenated (cis or trans) labdanes have been synthesised starting from sclareol. A new strategy that allows the obtention of diols α-cis as well as β-cis or trans is described. In particular, the syntheses of three natural highly functionalised labdanes in the B rings of 2, 3 and 4 with different side chains are reported. The syntheses have permitted to correct the proposed structure for one of them.