SelEXSIDE: Fast and Easy Measurement of Multiple-Bond ¹H,¹³C Coupling Constants for Stereochemical Analysis

Long-range ¹H,¹³C coupling constants (^<i>n</i><i>J</i>_CH) are underutilized parameters for stereochemical structure determination, primarily because they are not easy to measure. This report describes a rapid and easily interpreted method for the measurement of one or more ^<i>n</i><i>J</i>_CH values based on a ¹³C band-selective EXSIDE (SelEXSIDE), which reduces experiment times from many hours down to a few minutes while allowing a simple and straightforward readout of ^<i>n</i><i>J</i>_CH values from the resulting in-phase doublet signal

Quantitative NMR-Derived Interproton Distances Combined with Quantum Mechanical Calculations of ¹³C Chemical Shifts in the Stereochemical Determination of Conicasterol F, a Nuclear Receptor Ligand from <i>Theonella swinhoei</i>

Here we report the first application of combined accurate ROE-distance analysis with DFT calculations of NMR chemical shifts to achieve the relative configuration assignment of a marine natural product, conicasterol F, a new polyhydroxylated steroid isolated from the marine sponge <i>Theonella swinhoei</i>. We demonstrate the substantial advantages of this combined approach as a tool for structural studies of natural products, providing a powerful alternative to, or information to underpin, total synthesis when more classical NMR data analysis fails to provide unequivocal results. In this paper, we also describe the isolation and structure elucidation of conicasterol F and its 24-ethyl derivative, theonellasterol I, and their pharmacological evaluation as human nuclear receptor modulators