Biomedical subjects

James A Turner

Publications and source records attributed to James A Turner.

3 recordsLinked to original sources

PubMed2003

Diaryloxyacetate herbicides.

The discovery and investigation of a novel family of herbicides containing a diaryl acetal are described. The stability of the acetal limited herbicidal efficacy and recognizing that fact led to the design of analogs with commercial levels of post-emergence activity on broadleaf weeds. These compounds inhibited acetolactate synthase and in vitro activity data were used to guide target design. However, no members of this family provided a commercially valuable combination of herbicidal efficacy and crop selectivity.

Acetolactate Synthase↗

PubMed2002

Origin of enantiomeric selectivity in the aryloxyphenoxypropionic acid class of herbicidal acetyl coenzyme A carboxylase (ACCase) inhibitors.

Molecular modeling was used to propose an "active conformation" for the R-2-phenoxypropionic acid portion of the aryloxyphenoxypropionic acid series of herbicidal acetyl CoA carboxylase (ACCase) inhibitors. This candidate active conformation is a low-energy conformer with the R-methyl distal to the phenoxy fragment, stabilized by the generalized anomeric effect around the propionate ether bond; the inactive S-enantiomer has difficulty accessing this conformation due to steric interaction of the S-methyl with the o-hydrogen of the phenyl. This candidate conformation was challenged by preparation of a series of novel rigid analogues. ACCase inhibition data suggest that the systems which contain a fused five-membered, but not a six-membered, ring present the necessary pharmacophore to the active site of ACCase, confirming the active conformation hypothesis and demonstrating that the precise placement of the carboxylate relative to the phenyl group is more critical than the placement of the methyl.

Acetyl-CoA Carboxylase↗

PubMed2002

Synthesis and herbicidal activity of phenyl-substituted benzoylpyrazoles.

A novel series of substituted 3-phenyl benzoylpyrazoles were prepared and tested as potential grass herbicides. The targeted materials were prepared by three newly developed synthetic routes, which allowed a comprehensive study of the SAR (structure-activity relationships) of this series. The best combination of grass weed activity (Avena fatua L, Setaria viridis (L) Beauv and Alopecurus myosuroides Huds) and wheat selectivity was obtained with an alkoxy group in the 4-position of the phenyl ring. Activity was further enhanced by the presence of tert-butyl on the pyrazole and a methyl group at the C-2 position of the benzoyl moiety. The alkoxy-substituted 3-phenylbenzoylpyrazoles are a novel class of herbicides with potential utility for control of important grass weeds in cereals.

4-Hydroxyphenylpyruvate Dioxygenase↗