CARBON-13 NUCLEAR MAGNETIC RESONANCE SPECTRA OF VITAMINS D AND RELATED COMPOUNDS

Abstract

1. The natural abundance carbon-13 nmr of vitamins D (D₂ and D₃) and several isomers (5, 6-trans-vitamin D₂, isotachysterol₂ and isovitamin D₂) have been completely assigned by employing offresonance noise-decoupling, acetylation shifts, and lanthanide-induced shifts experiments. The last two techniques were especially useful for the present study.
2. Carbon-13 nmr spectral characteristics of the three main conjugated triene moieties (sE-Z-sZ, sE-E-sZ, or sE-E-sE), involved in the molecules of vitamin D and its isomers, were revealed. Thus, the striking dependence of the shieldings on molecular geometries and high sensitivity of the resonances to the environments of conjugated systems were surveyed.
3. Conformational preferences in solutions of the hydroxyl groups in vitamins D₂ and D₃ as well as 5, 6-trans-vitamin D₂ were conveniently determined.