| Abstract
| - Tandem Stille coupling and Diels−Alder reaction of steroidaliodoalkenyl substrates [17-iodoandrosta-16-ene (2),17-iodo-3-keto-4-methyl-4-azaandrosta-16-ene (10), and17-iodo-3-keto-4-azaandrosta-16-ene (11)] were examined in the presence ofvinyltributyltin, a dienophile (diethyl maleate,methyl acrylate, dimethyl acetylenedicarboxylate, diethyl fumarate,(−)-di[(1R)-menthyl] fumarate,maleic anhydride), and a palladium catalyst. The yields of novelpentacyclic steroids and thestereochemical outcome of the cycloaddition reaction were investigatedunder different reactionconditions. In some cases mixtures of isomers were formed, butwith dimethyl acetylenedicarboxylate, diethyl fumarate, (−)-di[(1R)-menthyl]fumarate, and maleic anhydride the products couldbe produced in good yields with high stereoselectivity. Theunequivocal assignment of stereoisomerswas carried out by various NMR techniques including1H−1H COSY and NOE experiments.
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