Abstract: Withajardins A-D are new class of withanolides isolated from the leaves of Deprea orinocensis and characterized by having a bicyclic C-17.beta. system and hydroxyl group at C-14 and C-17. The bicyclic system consists of a lactone and a homocyclic ring with six carbon atoms unlike the acnistins which have a five-membered homocyclic ring. The two classes of compounds were differentiated and their structures were identified by a series of HMQC, HMBC and finally X-ray diffraction experiments. Withajardins and acnistins would seem to evolve along quite dissimilar biosynthetic pathways although both types of compound show a marked immunosupressive effect on in vitro cultures of human lymphocytes.