FR901483, A NOVEL IMMUNOSUPPRESSANT ISOLATED FROM CLADOBOTRYUM SP NO-11231 - TAXONOMY OF THE PRODUCING ORGANISM, FERMENTATION, ISOLATION, PHYSICOCHEMICAL PROPERTIES AND BIOLOGICAL-ACTIVITIES

FR901483, a novel immunosuppressant, has been isolated from the fermen tation broth of Cladobotryum sp. No. 11231. The molecular formula of F R901483 has been determined as C20H31N2O6P. FR901483 exerts a potent i mmunosuppressive activity in vitro and significantly prolongs graft su rvival time in the rat skin allograft model. This compound has an intr iguing tricyclic structure possessing a phosphate ester in its molecul e. The ester residue may play an important role in exerting immunosupp ressive activity because the desphosphoryl compound is devoid of activ ity. It is thought that the primary target of immunosuppression by thi s compound is inhibition of purine nucleotide biosynthesis.