Desmethylcephalotaxinone and its correlation with cephalotaxine

A new alkaloid, desmethylcephalotaxinone (IIIa) has been isolated from Cephalotaxus harringtonia (Forbes) K. Koch var. harringtonia cv. Fastigiata. Its structure has been established by spectral methods and by a partial synthesis from cephalotaxine (Ia) via cephalotaxinone (II). Methylation of IIIa with dimethoxypropane yields II along with some isocephalotaxinone (IIIb). Compound II was confirmed as a naturally occurring minor Cephalotaxus constituent. Reduction of II with sodium borohydride proceeds stereospecifically to give Ia.