One-dimensional and two-dimensional NMR spectroscopy of sterols

Abstract

Whereas 13C NMR spectra of sterols and other steroids are normally subjected to a full signal assignment, it has been customary with 1H NMR spectra to assign only the methyl, olefinic, or carbinol protons whose signals are significantly deshielded relative to TMSi. The rest of the spectrum is often complicated by severe peak overlap as the remaining protons are distributed in a narrow spectral range between ~1 and 2.5 p.p.m., the so-called ‘methylene envelope’. Full 1H signal assignment of a steroid, 17β-hydroxyandrosta-l,4-diene, at 400MHz was performed in 1980 [1] by the use of a combination of the then recently developed one- and two-dimensional NMR techniques. Since that time, complete or nearly complete 1H NMR assignments for a number of steroids have been obtained with the aid of these various techniques [2–11]. This chapter describes some of the one-dimensional (1D) and two-dimensional (2D) NMR techniques most frequently used for the structure elucidation and signal assignments of sterols and related compounds.