Structural studies of loteprednol etabonate and other analogs of prednisolone using NMR techniques

Abstract

Severed structural analogy of prednisolone, prepared by esterification of the carboxylic and/or the C(17)-hydroxy group of 11β,17α-dihydroxy-3- oxo-androsta-1,4-diene-17β-carboxylic acid, were invextigated by NMR. Step- by-step analysis of the 1H and 13C NMR spectra of these steroids, including proton-proton selective decoupling, nuclear Overhuaser effect difference spectra, attached proton test, proton-carbon correlation (HETCOR), proton-proton correlation (COSY), and long-range proton-carbon decoupling (INAPT) techniques, led to unequivocat assignments of all their proton and carbon resonances. The stereochemical structure of loteprednol etabonate (chloromethyl 17α-ethoxycarbonyloxy-11β-hydroxy,-3-oxoandrosta-1,4 diene- 17β-carboxylate, 1), a soft corticosteroid antiinflammatory drug, was proved to be analogous to prednisolone.