Steve Fields | University of Wisconsin-Madison (original) (raw)

Papers by Steve Fields

Pure and Applied Chemistry, 1993

Abstract

Journal of the American Chemical Society, 1999

Oxazaborolidinones 3, 25, 32, 42, 49, and 53 can be obtained as single diastereomers by crystalli... more Oxazaborolidinones 3, 25, 32, 42, 49, and 53 can be obtained as single diastereomers by crystallization-induced asymmetric transformation (AT). Asymmetric memory is maintained in the derived enolates because the stereogenic boron resists equilibration with achiral, trivalent boron-containing species on the time scale of enolate alkylation with methyl iodide, allyl bromide, or benzyl bromide. Conditions were found for alkylating oxazaborolidinone enolates derived from phenylalanine (5, 33), alanine (18, 26), phenylglycine (43), and valine (54) without significant loss of boron configuration. The phenylglycine-derived oxazaborolidinone alkylation products 44 and 45 slowly undergo boron epimerization at room temperature, and the C-allyl product 44b partially racemizes during hydrolytic cleavage, apparently by a 2-aza-Cope rearrangement. These complications were not encountered with phenylalanine derivatives. Preparatively useful results were obtained with oxazaborolidinones 3 and 32, derived from phenylalanine. AT favors a different boron configuration in the B-naphthyl analogue 32 compared to 3. This provides access to either quasi-enantiomeric enolate 5 or 33 by starting from the same phenylalanine enantiomer.

Molecular biology of the cell, 2006

Sodium-dependent neurotransmitter transporters participate in the clearance and/or recycling of n... more Sodium-dependent neurotransmitter transporters participate in the clearance and/or recycling of neurotransmitters from synaptic clefts. The snf-11 gene in Caenorhabditis elegans encodes a protein of high similarity to mammalian GABA transporters (GATs). We show here that snf-11 encodes a functional GABA transporter; SNF-11-mediated GABA transport is Na+ and Cl- dependent, has an EC50 value of 168 microM, and is blocked by the GAT1 inhibitor SKF89976A. The SNF-11 protein is expressed in seven GABAergic neurons, several additional neurons in the head and retrovesicular ganglion, and three groups of muscle cells. Therefore, all GABAergic synapses are associated with either presynaptic or postsynaptic (or both) expression of SNF-11. Although a snf-11 null mutation has no obvious effects on GABAergic behaviors, it leads to resistance to inhibitors of acetylcholinesterase. In vivo, a snf-11 null mutation blocks GABA uptake in at least a subset of GABAergic cells; in a cell culture system,...

4-Aminopicolinic acids having aryl or heteroaryl substituents in the 6-position and their amine a... more 4-Aminopicolinic acids having aryl or heteroaryl substituents in the 6-position and their amine and acid derivatives are potent herbicides demonstrating a broad spectrum of weed control.

Bioorganic & Medicinal Chemistry, 2015

Multiple classes of commercially important auxin herbicides have been discovered since the 1940s ... more 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.

Organic Letters, 2002

9-Borabicyclononane (9-BBN) has been utilized to protect functionalized amino acids for potential... more 9-Borabicyclononane (9-BBN) has been utilized to protect functionalized amino acids for potential chemoselective side chain manipulation. The 9-BBN group imparts organic solubility to otherwise hydrophilic molecules and is tolerant of a wide range of reaction conditions. The high degree of solubility of these molecules in THF is particularly noteworthy. It is cleaved with either aqueous HCl or by exchange with ethylenediamine in methanol. [reaction: see text]

Tetrahedron Letters, 1998

Abstract Synthesis of the novel natural product Phosphonothrixin has been accomplished in 6 steps... more 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.

Tetrahedron Letters, 2010

An unusually high yielding fluorination of aminopyralid (3) using F-TEDA (SELECTFLUOR TM) in warm... more An unusually high yielding fluorination of aminopyralid (3) using F-TEDA (SELECTFLUOR TM) in warm water, followed by kinetic resolution (via iterative esterification/saponification) of the crude fluorination product with dry HCl in methanol produced pure ring-fluorinated pyridine 2 in an overall yield of 31% for the two steps.

Tetrahedron Letters, 1996

Trimethylsilyldiazomethane converts maleic anhydride derivatives in alcoholic THF to bisesters. T... more 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.