The cyclization transformation of the sulfonylurea herbicide flupyrsulfuron in the soil of winter wheat crops

Abstract

The synthesis of 1-(4,6-dimethoxypyrimidine-2-yl)-7-trifluoromethyl-1,2,3,4-tetrahydropyrido [2,3-d]pyrimidin-2,4-dione has been carried out in such a way that the dimethoxypyrimidine substituent was unambiguously in position 1 of the pyrido[2,3-d]pyrimidine ring. This regioisomer was obtained by cyclization with phosgene of 2-(4,6-dimethoxypyrimidin-2-ylamino)-6-trifluoromethylnicotinamide which had previously been ionized with sodium hydride. It was shown to be identical to the metabolite generated in the soil of winter wheat crops treated previously with the sulfonylurea herbicide flupyrsulfuronmethyl [(methyl 2-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)-6-trifluoromethylnicotinate]. The position of the dimethoxypyrimidine substituent had not previously been assigned unambiguously to positions 1 or 3 of the pyrido[2,3-d]pyrimidine ring. The regioisomer was also identical to the cyclization compound generated chemically from flupyrsulfuron in a sterile water buffer at pH 9. The metabolism pathways of flupyrsulfuron in soil are discussed in the light these structure determinations and compared with the soil metabolism pathways frequently observed with other sulfonylurea herbicides.

Selective Deamination of Mutagens by a Mycobacterial Enzyme

“…These compounds are commercially important. For example, 5-azacytosine and its derivatives are reported to have several applications in medicine and are used as chemotherapeutic agents, , whereas acetoguanide is a major degradation product of several s -triazines, which are an extensively used class of herbicides . Moreover, the precursor of ammeline, melamine, is a prominent food adulterant that has been associated with several pet and infant deaths and is considered an environmental hazard .…”

“…For example, 5azacytosine and its derivatives are reported to have several applications in medicine and are used as chemotherapeutic agents, 25,26 whereas acetoguanide is a major degradation product of several s-triazines, which are an extensively used class of herbicides. 27 Moreover, the precursor of ammeline, melamine, is a prominent food adulterant that has been associated with several pet and infant deaths and is considered an environmental hazard. 28 It appears that the Mycobacterium genus and other soil bacteria in group 5 have developed specific machineries to combat against these mutagens, thereby becoming resistant to these causative agents.…”