(±) Camptothecol, a pair of ditetrahydrofuran lignans enantiomers from the fruit of Camptotheca acuminate and structure revision of biphenylneolignan

Abstract

A new pair of enantiomers, (+) camptothecol (1a) and (–) camptothecol (1b), together with two known compounds (2 and 3), were isolated from the fruits of Camptotheca acuminate. Their chemical structures were elucidated by 1D and 2D NMR, quantum chemical calculations, as well as HR-ESI-MS spectroscopic analysis. Computational methods aided by the DP4+ probability technique and Computer-assisted structure elucidation (CASE) algorithms enabled structural reassignment of 2 and 3 to have a hydroxyfuran instead of a ternary epoxide. Structural revisions of the two compounds 2* and 3* were proposed.