Studies on griseolic acid derivatives. VII. Synthesis and phosphodiesterase inhibitory activity of the C4'-C5' hydrogenated products of griseolic acid and their base-exchanged derivatives.

Addition reactions of the C4'-C5' double bond of griseolic acid were investigated. C4'-C5' Dihydrogriseolic acid was obtained by reduction of the adduct having halogen at the 4'-position. The ring juncture of the two five-membered rings of the C4'-C5' dihydro derivatives was of all-"cis" configuration. Acetolysis of the protected dihydrogriseolic acid gave the corresponding 1 '-acetoxy sugar derivative. Reaction of this sugar derivative with silylated bases gave guanine and uracil derivatives of the dihydrogriseolic acid. The cyclic nucleotide phosphodiesterase (PDE)-inhibitory activity of the C4'-C5' cis dihydrogriseolic acid derivative was weaker than that of griseolic acid. The uracil derivative of C4'-C5' cis dihydrogriseolic acid completely lost the inhibitory activity against both adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) PDE, whereas the guanine derivative showed reduced inhibitory activity against cAMP PDE, but retained its activity against cGMP PDE. It was also apparent that the C4'-C5' trans dihydro derivative which was obtained as a minor product from the same culture broth of griseolic acid had almost the same inhibitory activity as griseolic acid. Keywords-griseolic acid; base-exchanged derivative; adenosine 3',5'-cyclic monophosphate; guanosine 3',5'-cyclic monophosphate; inhibitory activity; cAMP phosphodiesterase; cGMP phosphodiesterase