DECOUPLED PROTON NMR-SPECTRA

High-resolution proton NMR spectra are recorded in a new form where all resonances are singlets at the chemical-shift frequencies, with no spin-spin splittings. These ''decoupled'' proton spectra are derived from two-dimensional J spectra after real Fourier transformation (without frequency discrimination in F-1) so that each spin multiplet lies along both the 45 degrees and the 135 degrees diagonal, forming a pattern similar to St. Andrew's cross, with C-4 symmetry. The chemical shifts are located by searching for these centers of symmetry with a postacquisition data-processing algorithm. This is designed to facilitate the separation of overlapping and interpenetrating spin multiplets. The method is illustrated with applications to the 400 MHz high-resolution proton spectra of dehydrotestosterone and 4-androsten-3,17-dione. It is also possible to separate the spectra of components in a mixture and this is illustrated by breaking down the spectrum of an aqueous solution of D-glucose into subspectra from the ct and p anomers, in order to follow the time evolution of the mutarotation. (C) 1994 Academic Press, Inc.