Unambiguous assignment of 13C NMR signals in epimeric 4,5-epoxy-3-oxo-steroids assisted by X-ray diffraction and gauge invariant atomic orbitals calculation of absolute isotropic shieldings

Abstract

Complete assignments of the 13 C signals of diastereomeric 4,5-epoxy-3-oxo steroids based on a combination of 1D and 2D NMR techniques are described The assignments were corroborated or corrected by calculation of the absolute isotropic 13 C NMR shieldings using the Gauge Invariant Atomic Orbitals (GIAO) method at B3LYP/6-31+G(d,p) level.