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J(2,2*) = -14.0 J(23) = 6.8 J(2,3*) = 7.3 J(2*, 3) =7.3 J(2*, 3*)=6.8 J(34) = 6.8 J(3,4*) = 8.2 J(3*, 4) = 8.2 J(3*, 4*) = 6.8 J(4,4*)= -14.0 J(45) = J(4*, 5) = 6.7b J(5.6aa) =small J(5.6aS) = smallb J(5,7@)=smallb J(6aa,6ap)=15.OC J(6aa, 9) = 2 J(6a@, 91~8.9' J(7a, 78) = 14.8 J(3,3*) = -14.0 J(5.7a) = -O.!jb J(7a. 8) =small igi ' ' 1 = 8.7' J(8.12) = 9.7' J(9.10a) =7.7 J(lOa, 100) = 12.2 J(lOa, 11)=10.0 J(9,lOfl) = 8.2" J(lOP, 11)=7.OC J(11,12)=9.8 J(12, 13)=8.1d 20 0.89 J(19.20) = 6.8 Hz 'The proton chemical shifts and coupling constants are to first order, with the exception of H-2,2*, H-3,3* and H4,4* which were obtained from a spectral simulation. The coupling constants designated as small are difficult to measure.Value obtained from decoupled spectra. Value obtained from NOE difference spectra. Value obtained from inversion recovery spectra.

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The proton magnetic resonance (1H nmr) spectrum at 400 MHz of prostacyclin at pH 10.4 in glycine buffer has been completely analyzed utilizing homonuclear double resonance, inversion recovery, and difference nOe experiments. The spectral analysis shows that the two protons at C-4 are non-equivalent even though they are removed from the asymmetric centres at C-8 and C-9 by five bonds. The difference nOe measurements verify the configuration at C-5.Proton longitudinal relaxation times (T1) were measured at 400 and 200 MHz. From the T1 frequency dependence, effective rotational correlation times ranging from 2.3 × 10−10 to 3.0 × 10−10 s were calculated for H-5, H-9, H-11, and H-15. This indicates that the portion of the molecule encompassed by these protons has a longer correlation time than is observed for the C-2 and the C-17 to C-19 protons, for which the average correlation time is 1.2 × 10−10 s. Hence the aliphatic side chains have more segmental motion.