Protonenresonanzspektrosopie und Steroidstruktur. II. Die Lage der C‐18‐ und C‐19‐Methylsignale in Abhängigkeit von den Substituenten am Steroidgerüst

Abstract

Abstract The proton NMR spectra of 265 steroids of known structure have been recorded for 0,1M solutions in deuterochloroform and the positions of the signals of the 18‐and 19‐hydrogen atoms have been measured. The additional chemical shifts due to various substituents at many different positions of the steroid skeleton are compiled in a table. With its help most chemical shifts of the 18‐ and 19‐hydrogen atoms of these and unknown steroids may be computed with an accuracy of ± 0,015 ppm. An example show how to calculate the chemical shifts. The physical basis of teh influences due to substituents and double bond, as well as the reasons for the generally small deviations from the calculated chemical shifts, are reviewed and illustrated. The additional chemical shifts due to identical funcitonal groups in equivalent positions, i. e. in approximately the same steric relation to one of the tertiary methyl groups, are collected in a table. Possible reason for teh variation of these additional chemical shifts within sets of identical functional functional groups in equivalent positions are discussed. The table furnishes interesting insights into the conformation of certain steroids and shows the average values and deviations one has to reckon with if the chemical shifts on methyl groups in non‐steroidal compounds due to functional groups in corresponding positions to those in steroids are to be computed.