Structural characterisation of two pharmaceutically important steroids by solid-state NMR

Abstract

Several crystal modifications of two steroids (androsterone and beclomethasone dipropionate) have been characterised by solid-state NMR methods, and the chemical shifts between the different forms compared. The gradual loss of water from androsterone hemihydrate has been monitored by XRPD. The crystal structures are discussed in relation to the NMR data. That of the beclomethasone dipropionate ethyl acetate solvate has been determined for the first time. It is found that there are clear channels containing the ethyl acetate molecules, which are apparently not incorporated by hydrogen bonding. Carbon-13 CPMAS spectra with long contact times and MAS proton spectra are used to show the mobility of ethyl acetate molecules in the BDP solvate. The second-order effect of chlorine on the 13C spectrum of beclomethasone dipropionate monohydrate has been explored by varying the applied magnetic field.