Resolving Entangled J(H-H)-Coupling Patterns for Steroidal Structure Determinations by NMR Spectroscopy

For decades, high-resolution (1)H NMR spectroscopy has been routinely utilized to analyze both naturally occurring steroid hormones and synthetic steroids, which play important roles in regulating physiological functions in humans. Because the (1)H signals are inevitably superimposed and entangled with various J(H–H) splitting patterns, such that the individual (1)H chemical shift and associated J(H–H) coupling identities are hardly resolved. Given this, applications of thess information for elucidating steroidal molecular structures and steroid/ligand interactions at the atomic level were largely restricted. To overcome, we devoted to unraveling the entangled J(H–H) splitting patterns of two similar steroidal compounds having fully unsaturated protons, i.e., androstanolone and epiandrosterone (denoted as 1 and 2, respectively), in which only hydroxyl and ketone substituents attached to C3 and C17 were interchanged. Here we demonstrated that the J(H–H) values deduced from 1 and 2 are universal and applicable to other steroids, such as testosterone, 3β, 21-dihydroxygregna-5-en-20-one, prednisolone, and estradiol. On the other hand, the (1)H chemical shifts may deviate substantially from sample to sample. In this communication, we propose a simple but novel scheme for resolving the complicate J(H–H) splitting patterns and (1)H chemical shifts, aiming for steroidal structure determinations.