Synthese ab-trans-anellierter derivate des tricyclischen diterpens pleuromutilin durch intramolekulare 1,5-hydrid-verschiebung

The Diterpene Pleuromutilin(1) reacts with orthoformicacid-trimethylester at room temperature almost quantitatively to give the 11-keto-3-methylester 2 with AB-trans-configuration. This conversion is shown to occur through a 1,5-hydride-shift between C3 and C11. Treatment of 2 with Lewis acid (ZnCl₂) initiated a retro-1,5-hydride-shift which resulted in the formation of Pleuromutilin(1). Mechanistic aspects and structure assignments, which are based on chemical and spectroscopic (¹H- and ¹³C-NMR) data are discussed.