Carbon-13 Nuclear Magnetic Resonance Spectra of Prostaglandins and Some Prostaglandin Analogs

High-resolution pulsed Fourier-transform nuclear magnetic resonance spectroscopy at 22.63 MHz was used to observe the proton-decoupled natural-abundance13C nuclear magnetic resonance spectra of CDCl3solutions of the methyl esters of prostaglandins F1α , 15-epi-F1α, F2α, F2β, E2, A2, 13-dehydro-F2α, 13-dehydro-F3α, two intermediates on the synthetic pathway to 13-dehydro-PGF3α, and of 7-oxa-PGF1α. All resonances were assigned by chemical shift comparisons and single-frequency off-resonance proton decoupling. With two exceptions, all the lines of the spectra are well-resolved single-carbon resonances. Those due to the cyclopentane and vinyl carbons are most sensitive to structural changes. Some of these effects can be rationalized in terms of the preferred conformations of the molecules.