Fragranol A: a new class of spiro-triflavanoid hybrid with an unprecedented carbon skeleton from Anneslea fragrans

Abstract Phytochemical investigation of Anneslea fragrans twigs resulted in the discovery of fragranol A (1), a new class of structurally challenging and sterically hindered “spiro-triflavanoid” type compound possessing an unprecedented carbon skeleton. Fragranol A (1) consists of 45 carbons having six chiral carbons, including two spiro-chiral centers. Structural elucidation of 1 was achieved by HRFABMS, 1D and 2D NMR, analysis of spatial anisotropic effects, and quantum ECD calculations. A plausible biogenetic pathway of 1 is also proposed.