title: Complete 1H and 13C NMR spectra of pregnenolone.
abstract: Assignments for signals from 1H and 13C in the NMR spectra of pregnenolone (1), 16-dehydropregnenolone (2), and the 3-acetate of 1 (3) were validated by two-dimensional correlated spectroscopy (2D COSY) and heteronuclear single quantum coherence (HSQC). The narrow band of overlapping signals from H-7, H-2, and H-4 was resolved by exploiting three-bond coupling in the 2D COSY spectra and heteronuclear correlation. Assignments were based on high intensity cross peaks from long-range coupling by H-18 with H-17 and H-12 (axial). Similar cross peaks were observed for H-17 with H-21. Low intensity cross peaks were seen for H-4 coupled with H-6 and H-7, and also H-16 (quasi-axial) with H-14 of 1 and 3. Assignments based on 2D COSY spectra were confirmed by correlation peaks from HSQC. This now corrects the earlier conflicts among assignments reported for 13C signals of 1 and 3. Accurate assignments were similarly derived for signals from C-2, C-7, C-8, and C-21 of 1 and 3, and C-15 and C-16 of 1, 2, and 3. The complete sets of 1H and 13C NMR data for pregnenolone, pregnenolone 3-acetate, and 16-dehydropregnenolone serve as reference standards.
authors.affiliation: Institute of Organic Chemistry, Attila József University, Szeged, Hungary.
authors.forename: Z
authors.initials: Z
authors.lastname: Szendi
authors.forename: P
authors.initials: P
authors.lastname: Forgó
authors.forename: F
authors.initials: F
authors.lastname: Sweet
mesh_terms: D002247:Carbon Isotopes; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy; D011284:Pregnenolone / Q000031:analogs & derivatives / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; C003592:16-dehydropregnenolone; D011284:Pregnenolone; D006859:Hydrogen