A short synthesis of camptothecin via a 2-fluoro-1,4-dihydropyridine

Abstract

Addition of the enolate derived from isopropyl α-(methylsulfanyl)butyrate to N-(quinolylmethyl)-2-fluoro- pyridinium triflate 7, followed by oxidation–hydrolysis of the resultant 2-fluoro-1,4-dihydropyridine 8b afforded pyridone 9b, from which 20-deoxycamptothecin (11), a known precursor of camptothecin, was synthesized by a radical cyclization–desulfurization, with subsequent elaboration of the lactone E ring by chemoselective reduction.