Stephen Christopher Smith

Cyclic ketones and substituted α-keto acids as alternative substrates for novel Biginelli-like scaffold syntheses

The reactions of benzocyclic ketones and α-ketoacids as carbonyl components in the Biginelli reaction were investigated. These unusual Biginelli substrates furnished novel drug-like dihydropyrimidinone scaffolds suitable for further elaboration.

Encapsulation of palladium in polyurea microcapsules

An interfacial polymerisation approach is adopted to encapsulate palladium(II) acetate and palladium nanoparticles in polyurea microcapsules for use in catalysis.

Tandem cyclisation and [2,3]-Stevens rearrangement to 2-substituted pyrrolidines

Abstract Reaction of N-methylallylamine with diethyl meso-2,5-dibromoadipate in DMF at ambient temperature in the presence of potassium carbonate led directly to the two diastereomers of diethyl 2-allyl-N-methylpyrrolidine-2,5-dicarboxylate. The reaction proceeds via a [2,3]-sigmatropic Stevens rearrangement, which occurred spontaneously under the reaction conditions. This gave a higher yield under milder conditions than the traditional Stevens reaction of diethyl N-allylpyrrolidine-2,5-dicarboxylate with iodomethane. The sequence was a key step in the synthesis of a series of analogues of the alkaloid stemofoline.

Double decarboxylative Claisen rearrangement reactions: microwave-assisted de novo synthesis of pyridines

Microwave-assisted double decarboxylative Claisen rearrangement of bis(allyl) 2-tosylmalonates provides substituted 1,6-heptadienes, which may be alkylated, and then converted into pyridines by ozonolysis followed by reaction with ammonia generated in situ under microwave conditions.

Targeting Chemical Inputs and Optimising HTS for Agrochemical Discovery

In vivo high throughput screening (HTS) has been adopted by most of the larger crop protection companies as an important tool for the discovery of new agrochemicals. There has been a paradigm shift in capabilities from screening a few thousand compounds a year to several hundred thousand and the quantity of screening sample required has fallen dramatically. The unifying goal now bringing together screens and inputs is the need to maximise the flow of useful information from HTS and thereby minimise the time taken to discover robust leads and new products. This review examines the positive changes that have occurred towards targeted design and selection of chemical inputs for agrochemical discovery over the last ten years and corresponding developments in HTS assays, data analysis and the logistics of compound storage and dispensing.

Combinatorial chemistry in the development of new crop protection products

Stephen Smith from Syngenta at Jealotts Hill International Research Centre in the UK describes the impact that combinatorial chemistry is having on the discovery process in the crop protection industry.

Synthesis and agrochemical screening of a library of natural product-like bicyclo[2,2,2]octenones

A general route to a series of differentially substituted bicyclo[2,2,2]octenones has been developed, making use of the in situ intramolecular Diels Alder reaction of masked ortho-benzoquinones. This approach was used to synthesize a series of thirteen key acid-containing templates from which a solution phase discovery library of 1126 diverse amides was then constructed. The rigid polycyclic nature of the templates and the prevalence of oxygenated functionality confer natural product-like qualities and three-dimensional diversity. The library was screened in HTS in vivo against a number of weed, insect and fungal model organisms leading to the discovery of a novel series of herbicidally active compounds. The development, production and biological activity of the library are described.