Novel synthetic approaches to prostanoic acid derivatives

The singlet and triplet photochemical behaviour of β,γ-unsaturated ketones is reviewed. The synthesis of 5-acetoxy-2,2-dimethylcyclohept-3-enone (95) is described and attempts to prepare other 5-substituted cycloheptenones are reported. The photolysis of acetate (95) gave 2-isobutenylcyclopent-2-enone (99) and attempts to elaborate this molecule to a prostanoic acid derivative are described. Syntheses of prostaglandins are reviewed with particular emphasis on the Harvard iodolactone approach and those routes involving the base catalysed condensations of dicarbonyl compounds. The Claisen condensation of diethyl azelate and undecan-2-one to give ethyleicos-9,11-dionoate (179), the subsequent methylation to give ethyl-10,10-dimethyleicos-9,11-dionoate (185), and the successful cyclisation to ethyl 10,10-dimethylprost-8,(12)-on-9,11-dionoate (188) using sodium ethoxide and iodine are reported. Attempts are also outlined on the use of benzylidene and hydroxymethylene as removable protecting groups for C-10. Finally the syntheses of substituted undecan-2-ones are described and attempts to utilise them in the general synthetic sequence outlined above are reported.