Prostaglandin chemistry—VIII : Synthesis of optically active 7-oxoprostaglandins

Regiospecific α-acylation of β-alkenylated enolates generated by conjugate addition of lithium organocuprates to α,β-unsaturated ketones is described. Several new 7-oxoprostaglandin analogues, 7-oxoprostaglandin E₁ (18), 11-deoxy-7-oxoprostaglandin E₁ (23), and their 15-epi enantiomers 17 and 22, were synthesized by conjugate addition-acylation method. From optically active 4(R) -t - butyldimethylsiloxycyclopent - 2 - en - 1 - one (R-11), 7-oxoprostaglandin E₁ (18) was synthesized. Determination of the absolute configuration of 11-deoxy-7-oxoprostaglandin E₁ (23) and its 15-epi enantiomer (22) on the basis of CD study is described. Successful acylation of β-alkenylated lithium copper enolates with reactive acylating agents such as thiol esters and N-acyl imidazole as well as acyl halides is described.