NAPHTHOQUINONE ESTERS FROM THE ROOT OF RHINACANTHUS-NASUTUS

Reinvestigation of the root of Rhinacanthus nasutus afforded, in addit ion to rhinacanthin-A to -D reported previously, two new dimethyldihyd ropyranonaphthoquinone esters (5, 6) and eight new 2-hydroxy-1,4-napht hoquinone esters (7-14) were isolated, The stereochemistry of rhinacan thin-A was determined as the R configuration, Compounds rhinacanthin-G to -N, belong to a class of -(3-hydroxy-2,2-dimethylpropyl)-1,4-napht hoquinone esters, and so far have been isolated only in this plant, Th eir biosynthesis is also discussed.