GS-13005 [0,0—dimethyl S-[2-methoxy-1,3,4-thiadiazol-5-(4H) ony1l-(4) methyl ]- 
dithiophosphate ] 
Rats were dosed orally with labeled GS-13005. Distribution patterns 
indicated complete absorption and intense metabolism of the compound with 
cleavage of the heterocyclic to CO, as the main result. GS-13005 was 
distributed rapidly but the radioactive content of all organs was below the 
limit of detection 48 hours after dosage except for traces in the muscles. 
Most of the dose was excreted in the urine as polar metabolites or expired. 
The most important metabolites observed were 4-methylsulfinylmethyl- and 4- 
methylsulfonyl-2-methoxy-1,3,4-thiadiazole-5-one. These metabolites origi- 
nate by methylation and oxidation of the mercaptomethyl derivative liberated 
after hydrolysis of the P-S bond (418, 1566). Dimethyl phosphate, dimethyl 
phosphorothioate, methyl phosphate, inorganic phosphate and desmethyl GS-13005 
were also found in urine and/or feces (1629). 
Young bean plants (Phaseolus vulgaris L.), to which GS-13005 had been 
applied, also split the heterocyclic moiety of the insecticide to CQ). 
Small amounts of unidentified metabolites were also detected (418). 
Cotton plants of the Delta-pine Smoothleaf variety were grown and 
treated with P34-labeled GS-13005. Examination of various parts of the 
plants revealed the presence, in varying amounts, of desmethyl GS-13005, 
the oxon (or thiolate) analog of GS-13005, dimethyl phosphorothiolate, mon- 
and di-methyl phosphate, inorganic phosphate, an unidentified metabolite, 
and some unextracted radioactivity. The latter probably represented incor- 
poration of liberated inorganic P°4 into natural plant constituents (1629). 
In 5th instar tobacco budworms, GS-13005 was completely metabolized 
uring the first 4 hours. Small amounts of the thiolate analog and the 
desmethyl analog formed during this time but was depleted after 4 hours. 
Dimet’:yl phosphorothioate and dimethyl phosphate were the major hydrolytic 
p..oducts detected in internal extracts and excreta. Other unidentified polar 
metabolites were also observed (1629). 
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