Structure-Biodegradability Relationships of Dialkyl Dithiolanylidenemalonates in Rice Plants and Rat Liver Homogenate

All dialkyl 1, 3-dithiolan-2-ylidenemalonates examined are considerably stable in rice plants, showing their t1/2 of 2.0-3.8 days. A non-cyclic analog with the t1/2 of 0.8 day, however, is rapidly metabolized probably through the oxidation at its thioether groups. Although the rat liver homogenate has both oxidation and hydrolysis activities, it shows predominantly the esterase activity in the absence of NADPH. In the rat liver homogenate, again, the non-cyclic analog is much more susceptible to oxidative metabolism in the presence of NADPH than, but as stable against the ester hydrolysis as the cyclic counterparts. The ester hydrolysis rates of the compounds well relate to the branching (s) at the α-position or the resulting electronic (σ*) or steric (Ecs) effects of alcoholic alkyl groups.