Photoadditions of enones 4 or 18 with cyclopentene gave in good yield adducts 516 or 20121, respectively, with the anti isomers predominating by a ratio of-9: l. These adducts were converted to hydroxy ketones 9 or 24 by the following sequence: ketalization, LiAlH4 reduction, and hydrolysis. The alcohol function in these ketones was converted to a good leaving group, and the resultant derivatives were solvolyzed to give ring-expanded ...