Abstract Alkylation of bicyclo [3.3. 0] octane-2, 8-dione (1), which is prepared by a modification of the procedure described in the literature, gives the methyl-and propynyl- derivatives 6 and 7 (Scheme 1). In addition to the method described previously (Scheme 2), 9-methyl-cis-decalin-1, 8-dione 9 is obtainable stereoselectively either by cyclization of keto- acid 16, or by aldol cyclization of keto-aldehyde 26 and oxydation of the resulting alcohols ...
