STEREOCHEMISTRY OF 3-OXO-5-PHENYLCYCLOPENTANECARBOXYLIC ACIDS .9. SYNTHESIS OF STEREOISOMERIC 5-(FLUOROPHENYL)-3-OXOCYCLOPENTANECARBOXYLIC ACIDS

The stereoselective synthesis of the cis- and trans 5-(fluorophenyl)-3-oxocyclopentanecarboxylic acids 5a-d/6a-d by combined Michael and Dieckmann reaction from trimethyl ethanetricarboxylate and the fluorinated methyl cinnamates 1a-d is described. Acidic and basic degradation of the trimethyl 5-phenyl-3-oxocyclopentane-1,1,t-4-tricarboxylates 2a-d proceeds via the 5-phenyl-c-1-methoxycarbonyl-3-oxocyclopentane-t-1-carboxylic acids 3a-d and the 5-phenyl-3-oxocyclopentane-1,1-dicarboxylic acids 4a-d. The structures were determined by diazomethane esterification of 5a-d to 7a-d, 6a-d to 8a-d, 3a-d and 4a-d to 9a-d.