The key compound 9 was readily prepared in larger quantities by an improvement of a known procedure. Addition of carbanions to the unprotected ketone 9 gives the hydroxy ketones 16-21 via the acetals 10-15. Dehydration of 16-20 furnishes the dienones 2-6 while 7 is available in fair yield via the acetoacetate 21. Through intramolecular cyclization also the ester 26 is formed which affords with NaOH the keto ester 29 by a retro-Michael ...
