Biological activity of alkyl 2-(acylthio)benzoates

Of a series of synthetic alkyl 2-(acylthio)benzoate (1-20), all the derivat ives except for n-butyl 2-butyrylthiobenzoate (18) and n-butyl 2-n-valerylt hiobenzoate (20) showed clear photogrowth-inhibitory activity. All the comp ounds tested except for methyl 2-butyrylthiobenzoate (3) exhibited cytotoxi c activity on mouse splenic T cells, Strong phytogrowth-inhibition and cyto toxic activity were found with 1, 6, 11 and 16 with an acetylthio group at C-2, suggesting that the acetyl group seems to play an important role in bo th activities of alkyl 2-(acylthio)benzoates. Among them, methyl 2-acetylth iobenzoate (1) was the strongest inhibitor. On the other hand, potent inhib ition of prolyl endopeptidase was exhibited by 2, 7, 12 and 17 with a propi onylthio group at C-2. These findings imply that a propionyl group might be useful for increasing the inhibitory activity against on prolyl endopeptid ase.