A variable-temperature ¹³C NMR study of (η⁵-C₅H₅)₂Mo₂(CO)₄ complexes of chiral alkynes derived from a terpene or a hormonal steroid: interconversion of diastereomers via exchange of terminal and semi-bridging carbonyls

Abstract

the steroidal hormone 11P-(4-dimethylaminopheny1)-17P-hydroxy-17a-(1-propyny1)-estra-4,9-dien-3-one (RU 38486) or with propynylborneol yields in each case a chiral cluster that exhibits two cyclopentadienyl resonances in both the 'H and I3c NMR regimes. At low temperature the interconversion of diastereomers arising from the different orientations of the semi-bridging carbonyl ligand can be slowed on the NMR time scale. The barrier to diastereomer interchange has been determined for the terpenoid cluster and the mechanism of this process is discussed. La reaction du (C,H,)IMo,(CO)4 avec l'hormone steroidale 11~-(4-dim~thylamino)-17~-hydroxy-17a-(l-propynyl)-estra-4,9-dikn-3-one (RU 38486) ou avec le propynylborneol conduit dans chaque cas h un cluster chiral qui presente deux resonances de cyclopentadienyles en RMN tant du 'H que du I3c. A basses temperatures, sur 17Cchelle de temps de la RMN, on peut ralentir l'interconversion des diaster~oisom&res provenant des differentes orientations dans le ligand carbonyle agissant comme demi-pont.[Traduit par la redaction]

Synthesis of Transition-Metal Steroid Derivatives

“…Compounds 475 and 476a , b were thus directly generated, respectively, from ethisterone 119 and mefipristone 449 (Figure ) and isolated in reasonable to excellent yields. Compound 476b was thoroughly studied by NMR spectroscopy by McGlinchey et al, and the existence of several diastereomers (due to the chirality introduced by the organometallic moiety) was evidenced at low temperature …”