METABOLIC PRODUCTS OF MICROORGANISMS. 261 OBSCUROLIDES, A NOVEL CLASS OF PHOSPHODIESTERASE INHIBITORS FROM STREPTOMYCES: I. PRODUCTION, ISOLATION, STRUCTURAL ELUCIDATION AND BIOLOGICAL ACTIVITY OF OBSCUROLIDES A1 TO A4

A novel class of butyrolactones, named obscurolides, was isolated from the culture nitrate of Streptomyces viridochromogenes by chemical screening methods. The structural elucidation of the obscurolides A1 to A4 (1-4) is described. The carboxy group of the 4-aminobenzoic acid moiety of obscurolide A1 (1) is reduced in the other compounds. The isolated natural products have been proved to be diastereomeric mixtures by a partial racemization at C-7 which belongs to an allylic alcohol system. The obscurolides showed a weak inhibitory activity against calcium/calmodulindependent and independent phosphodiesterases from bovine.