Synthesis and insecticidal activity of N-(5-phenylpyrazin-2-yl)-benzamide derivatives: Elucidation of mode of action on chitin biosynthesis through symptomology and genetic studies.

Among the six-membered heterocycles, the pyrazine ring is poorly explored in crop protection and does not feature in any product listed in the current IRAC MoA classification. In an effort to identify new leads for internal research, we synthesized a series of N-(5-phenylpyrazin-2-yl)-benzamide derivatives and evaluated them for their insecticidal activity. N-(5-phenylpyrazin-2-yl)-benzamide derivatives 3 were prepared using an automated two-step synthesis protocol. These compounds were tested for their initial biological activity against a wide range of sucking and chewing insect pests and found to be active against lepidopterans only. More detailed experiments, including symptomology studies on the diamondback moth, Plutella xylostella (L.) and the Egyptian cotton leafworm, Spodoptera littoralis (Boisduval) showed that analog 3q causes severe abnormalities in the lepidopteran cuticle leading to larval mortality. Compound 3q shows strong potency against both P. xylostella and S. littoralis, whereas analog 3i shows better potency against S. littoralis causing also impaired cuticular structure and death of the larvae. Additionally, P. xylostella genetic studies showed that compound 3q resistance is linked to Chitin Synthase 1. Our studies show that N-(5-phenylpyrazin-2-yl)-benzamide derivatives 3, and in particular analogs 3i and 3q, act as insect growth modulator insecticides. Conformational similarities with lufenuron are discussed.

The Bioorthogonal Isonitrile-Chlorooxime Ligation.

Bioorthogonal reactions are valuable tools for the selective labeling and imaging of natural products and proteins. Here, we present the reaction between isonitriles and chlorooximes as a ligation that proceeds quickly (k ≈ 1 M-1 s-1) and with high chemoselectivity in an aqueous environment. Imaging of metabolically labeled cell surface glycans underlined the tolerance of the ligation to common functional groups in cellular systems. Live-cell dual-labeling experiments revealed that the isonitrile-chlorooxime ligation is orthogonal to the strain-promoted azide-alkyne cycloaddition.

The Rabe amination after a century: direct addition of N-heterocycles to carbonyl compounds.

A catalytic version of the Rabe electrophilic amination is presented. This kind of reaction was originally employed in 1918 in a key step for the conversion of quinotoxine to quinine. Ketones and α-substituted aldehydes give the corresponding α-aminated carbonyl compounds in moderate yield. α,α-Unsubstituted aldehydes give rise to amino ketones via a novel rearrangement.

Biomimetic organocatalytic asymmetric synthesis of 2-substituted piperidine-type alkaloids and their analogues.

Natural substances such as pelletierine and its analogues have been prepared in up to 97% ee and good yield by a protective-group-free, biomimetic approach. Usage of benzonitrile or acetonitrile as solvents effectively prevents product racemization.

Unsaturated beta-ketoesters as versatile electrophiles in organocatalysis.

Beta-ketoesters, which have widely been employed as nucleophiles, are also useful electrophiles in organocatalytic quinine mediated cascade reactions, leading to the formation of products bearing multiple stereocenters in high stereoselectivity.