We have synthesized different 713-derivatives of the diterpene forskolin, which are presumably more hydrophilic than the parent compound. Their activity was tested on the adenylate cyclase system of human platelet membranes. The 713-glyceryl and 713-dimethylacryloyl derivatives were as potent as native forskolin while 7-deacetylforskolin was 10 fold less active. Pyranosyl derivatives were unable to stimulate adenylate cyclase although they displayed a weak antagonistic effect against forskolin activation.