Synthesis and evaluation of the molluscicidal activity of the 5,6-dimethyl-dihydro-pyran-2,4-dione and 6-substituted analogous.

Five dihydro-piran-2,4-diones, including 5,6-dimethyl-dihydro-piran-2,4-dione one of the intermediates of the synthesis of caloverticilic acid, were synthesized and submitted to molluscicidal bioassay. The compound's yields varied from moderate to good (42%- 80%) and were achieved through the preparation of the dianion of ethyl acetoacetate, reaction with and aldehyde followed by hydrolysis of the ester (NaOH, H(2)O, 2 h, T.A.) and lactonization in acidic medium (HCl, 0 degrees C). The 5,6-dimethyl-dihydro-piran-2,4-dione and three analogous dihydro-piran-2,4-diones 6-substituted,-phenyl, (4-methoxy-phenyl), and -propenyl, showed significant activities against the Biomphalaria glabrata egg masses, while the analogous 6-(3,4-dimethoxy-phenyl) was inactive as molluscicide. This activity is reported for the first time, extending the range of biological activities of this group.