Synthesis of Saframycins. X. Transformation of (-)-Saframycin A to (-)-Saframycin Mx Type Compound with the Structure Proposed for Saframycin E

Abstract

Treatment of (-)-saframycin A (1a) with selenium oxide in acetic acid afforded (-)-saframycin G (1g), and a catalytic reduction and regionselective oxidation sequence afforded the saframycin Mx type compound (3). We applied this methodology to the transformation of (±)-5-hydroxysaframycin B (11) to the hydroquinone (1e). Acetylation of 1e with acetic anhydride in pyridine gave the triacetate (13), which is identical with the triacetyl derivative of natural saframycin E.