
Captan (N-Trichloromethylthio~4-cyclohexene-1, 2-dicarboximide) 
The intercellular breakdown product of captan, thiophosgene, is 
capable of inhibiting certain enzyme systems that have cocarboxylase as 
a coenzyme (387, 692, 797, 911). Captan reacted with sulfhydryl com 
pounds, in general, such as cysteine and glutathione (889, 1121, 1208, 
1310). The reaction does not occur below pH 4.0 or 5.0, respectively, 
and the rate rises rapidly above pH 6.0 (889). Products of the reaction 
with cysteine were cystine, tetrahydrophthalimide, hydrogen sulfide, 2- 
thiazolidinethione-4-carboxylic acid, HCl, and what was then believed to 
be carbon disulfide. The trichloromethylthio group and thiophosgene 
were apparently intermediates in the formation of 2-thiazolidinethione-4- 
carboxylic acid. From aqueous solutions of thiophosgene, a compound with 
the melting point of di(thiophosgene) was isolated (912). Recent studies 
have indicated that the lack of specificity of Viles solution led to the 
erroneous identification of one metabolite as carbon disulfide. Infrared 
and gas chromatographic analyses have shown that this compound, derived 
either from the reaction of captan and glutathione or from the reaction 
of captan with N. crassa spores, was in fact carbonyl sulfide (1336). 
Although captan did not appear capable of reacting with other than 
sulfhydryl groups, the trichloromethyl group of phosgene released from 
captan by sulfhydryl groups was apparently capable of reacting with amino, 
hydroxy), sulfhydryl, and possibly other groups. Histidine and serine re- 
acted with thiophosgene to form UV-absorbing compounds (911, 912). 
Saccharomyces cerevisiae degraded captan to thiophosgene and 
di(thiophosgene) (910). 
Captan has been shown to react with NaDDC, Zn(DDC),, and 
Fe (DDC), (909). 
Captan + DDC + Bis(dimethylthiocarbamyl)trithiocarbonate 
TMTD + TMTM + Cl + COS 
69 
