RHODES
Metabolism of [2-14C]Terbacil in Alfalfa Robert C. Rhodes Alfalfa, treated with [ 2-14C]terbacil(3-tert-butyl-5-chloro-6-methyluracil) in the dormant stage at a rate of 1lb of active ingredient/acre, contained average radiochemical residues of 2.2 and 0.4 ppm (calculated as terbacil) at the first and second harvests, 6 and 8 months after treatment, respectively. TLC analyses of extracts from the treated alfalfa showed a total of six 14C-labeled areas. Three compounds were identified by mass spectral analyses; terbacil (12.5% of the 14C in the extract), 3-tert-butyl-5-chloro6-hydroxymethyluracil (metabolite A, 11.9%) and 6-chloro-2,3-dihydro-7-(hydroxymethyl)-3,3-dimethyl-5H-oxazolo[3,2-a]pyrimidin-5-one (metabolite B, 41.2%). The structures of metabolites C and D, 18.3 and 5.670, respectively, were assigned on the basis of their Rf values on the TLC plates. The remainder of the 14Cactivity (10.5%) was material at the origin of the TLC plate. No 5-chlorouracil was detected (
