5-Methoxyjusticidin A, a new arylnaphthalene lignan from Protium unifoliolatum.

A new arylnaphthalene lignan, 9-(1,3-benzodioxol-5-yl)-4,5,6, 7-tetramethoxynaphtho[2,3-C]furan-1(3H)-one (5-methoxyjusticidin A, 1), was isolated from a Et2O extract of the wood of Protium unifoliolatum. The structure of 1 was determined by both spectroscopic and X-ray crystallographic methods.