A stereochemical examination of the equine metabolism of 17α-methyltestosterone

An investigation was conducted into the stereochemistry of the equine urinary metabolites of 17 alpha-methyltestosterone observed after oral administration. Standards of the complete range of C3/C5/C16 stereoisomeric 17 alpha-methylandrostane-3,17 beta-diols, 17 alpha-methylandrostane-3,16,17 beta-triols and 17 alpha-hydroxymethylandrostane-3,17 beta-diols were purchased or synthesised, and were used to unequivocally identify the absolute structures of the metabolites. Phase I metabolism was found to involve combinations of Delta(4)-3-ketone reduction with both 5 alpha,3 beta- and 5 beta,3 alpha-stereochemistry, hydroxylation at C16 with both 16 alpha- and 16 beta-stereochemistry and hydroxylation of the 17 alpha-methyl substituent. Phase II metabolism involved mainly sulfation with a lesser degree of beta-glucuronidation. (c) 2006 Elsevier B.V. All rights reserved.