Stephen Craig Fields

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.

Total synthesis of (±)-8′-trifluoromethyl abscisic acid

Abstract While 8′-trifluoromethyl ABA ( 2a ) was known to be one of the most active and stable analogs tested in assays for ABA-like activity, a thorough evaluation of its biological properties was limited by compound availability. The current synthesis, which includes the preparation of a previously unknown key intermediate 2-methyl-2-trifluoromethyl-1,4-cyclohexanedione-mono ethylene ketal ( 18 ), has been accomplished in 14 steps and 3% yield. The key fluorinated ketal intermediate 18 was prepared in six steps and 20% yield.

TOTAL SYNTHESIS OF ()-PHOSPHONOTHRIXIN

Abstract Synthesis of the novel natural product Phosphonothrixin has been accomplished in 6 steps and 24% overall yield from the commercially available Baylis-Hillman adduct derived from acetaldehyde and methyl vinyl ketone. The synthesis features use of a trisubstituted olefin as a latent a-hydroxyketone, which formally reverses the oxidation states of the hydroxyl and carbonyl functionalities. This alleviates some of the difficulties encountered in alternative syntheses which proceed through metastable intermediates.

Bis-esters from maleic anhydrides under neutral conditions: Protection of the anhydride of the natural product cornexistin

Abstract Trimethylsilyldiazomethane converts maleic anhydride derivatives in alcoholic THF to bisesters. The highly acid and base sensitive natural product cornexistin was converted to its bis-methyl ester in 70–75% yield and to the mixed benzyl/methyl ester in 61% yield. The mixed ester can be converted back to cornexistin via transfer hydrogenation.