Nicholas Martin Irvine

The discovery of Arylex™ active and Rinskor™ active: Two novel auxin herbicides.

Multiple classes of commercially important auxin herbicides have been discovered since the 1940s including the aryloxyacetates (2,4-D, MCPA, dichlorprop, mecoprop, triclopyr, and fluroxypyr), the benzoates (dicamba), the quinoline-2-carboxylates (quinclorac and quinmerac), the pyrimidine-4-carboxylates (aminocyclopyrachlor), and the pyridine-2-carboxylates (picloram, clopyralid, and aminopyralid). In the last 10 years, two novel pyridine-2-carboxylate (or picolinate) herbicides were discovered at Dow AgroSciences. This paper will describe the structure activity relationship study that led to the discovery of the 6-aryl-picolinate herbicides Arylex™ active (2005) and Rinskor™ active (2010). While Arylex was developed primarily for use in cereal crops and Rinskor is still in development primarily for use in rice crops, both herbicides will also be utilized in additional crops.

Synthesis and characterization of synthetic analogs of cinnacidin, a novel phytotoxin from Nectria sp.

BACKGROUND The novel natural product cinnacidin was isolated from a fungal fermentation extract of Nectria sp. DA060097. The compound was found to contain a cyclopentalenone ring system with an isoleucine subunit linked through an amide bond. Initial biological characterization of cinnacidin suggested promising herbicidal activity. RESULTS Two synthetic analogs, (2S,3S)-2-[(3RS,3aSR,6aRS)-3-methoxy-4-oxo-3,3a,4,5,6,6a-hexahydropentalen-1-ylcarbamoyl]-3-methylvaleric acid and benzyl (2S,3S)-2-[(3RS,3aSR,6aRS)-3-methoxy-4-oxo-3,3a,4, 5,6,6a-hexahydropentalen-1-ylcarbamoyl]-3-methylvalerate, were prepared for further characterization, and their herbicidal activities were compared with that of cinnacidin. CONCLUSIONS The synthetic compounds were highly phytotoxic on a range of weeds. Based on the symptoms in treated plants, the mode of action of these compounds is suggested to be similar to that of coronatine and jasmonic acid. Coronatine was more active against warm-season grasses, while the cinnacidin benzyl ester analog was more effective on cool-season grasses. In a seedling growth bioassay conducted on bentgrass, the cinnacidin analog was equivalent in activity to coronatine.

Characterization of two hydroxytrichloropicolinic acids: application of the one-bond chlorine-isotope effect in 13C NMR.

The structures of 4‐hydroxy‐3,5,6‐trichloropyridine‐2‐carboxylic acid (1a) and 6‐hydroxy‐3,4,5‐trichloro‐2‐carboxylic acid (1b) were verified by the NMR analysis of their corresponding methylated and decarboxylated derivatives 2,3,5‐trichloro‐4‐methoxypyridine (5) and 3,4,5‐trichloro‐2‐methoxypyridine (8), respectively. The 6‐hydroxy isomer (1a) was found to be in equilibrium with its pyridinone tautomer as evidenced by the formation of significant amounts of 3,4,5‐trichloro‐1‐methyl‐6‐oxo‐1,6‐dihydropyridine‐2‐carboxylic acid methyl ester (6b) on exhaustive methylation. The one‐bond chlorine‐isotope effect was used and shown to be an effective tool for the identification of chlorinated carbons in 13C NMR spectra providing an additional tool for solving structural problems in chlorinated compounds. Copyright