CHEMISTRY OF THE SCROPHULARIACEAE .14. IRIDOID GLYCOSIDES AND A PYRIDINE MONOTERPENE ALKALOID FROM ORTHOCARPUS - NEW ARTIFACTUAL IRIDOID DIENALS

Euphroside [1] was found to be the major iridoid of Orthocarpus purpureoalbus, Orthocarpus luteus, Orthocarpus tolmei, and Orthocarpus tenuifolius, all species of the Section Orthocarpus in the genus Orthocarpus (Scrophulariaceae). Small amounts of plantarenaloside, adoxoside, ixoroside, geniposidic acid, and mussaenosidic acid were encountered in some of the species. Two closely related new iridoid glucoside dienals 2 and 3, which appeared to be the MeOH adducts from a bisdehydration process on euphroside [1], were isolated from extracts of all species. Attempts to prepare the dienals by dehydration of euphroside [1] were unsuccessful and yielded a monodehydrated MeOH adduct 6 rather than the isolated dienals. Euphrosine [16], a new pyridine monoterpene alkaloid, was isolated from O. luteus. It was synthesized from 1 through the intermediacy of 6. © 1990, American Chemical Society. All rights reserved.