for example episclareolid and isosclareolid reducing the cyclization product to the corresponding diol mixed and finally dehydrating the diol product a typical multistage process for the conversion of the compound s of formula i into the mixture of 3a u03b1 5a u03b2 9a u03b1 9b u03b2 dodecahydro3a 6 6 9a tetramethylnaphthol 2 1 b furan and 3a u03b1 5a u03b2 9a u03b1 9b u03b1 dodecahydro3a 6 6 9a tetramethylnaphtho 2 1 b furan is given in the following reaction scheme in which the notations 34 34 and 34 34 signify that the corresponding residue is situated above and respectively below the plane of the molecule str5 according to lucius archiv der pharmazie 291 55 1958 chem ber 1960 2663 angew chem 68 247 1956 and ddr patent 13535 the cyclization can be carried out using a mixture of formic acid and sulphuric acid although the exact stereochemistry of the thus obtained three lactones could not be characterized unequivocally a saito et al chem lett 1981 757 760 and chem lett 1983 729 732 have investigated the cyclization in detail and have assigned the exact stereochemistry to these lactones this cyclization comprises treating e 6 2 39 6 39 6 39 trimethyl cyclohex 1 39 en 1 39 yl 4 methyl hex 3 enoic acid ia with tin tetrachloride in methylene chloride at 78 u00b0 c which gives a mixture of u00b1 sclareolid and u00b1 episclareolid in a weight.