Urs Müller

Synthesis and fungicidal activity of tubulin polymerisation promoters. Part 1: pyrido[2,3-b]pyrazines.

BACKGROUND The excellent fungicidal activity of [1,2,4]triazolo[1,5-a]pyrimidines suggested the search for further analogues with improved properties. RESULTS A series of novel trisubstituted pyrido[2,3-b]pyrazines has been designed and prepared as 6,6-biheterocyclic analogues of related 5,6-bicyclic [1,2,4]triazolo[1,5-a]pyrimidines. Their fungicidal activity was evaluated against the plant pathogens Puccinia recondita Rob. ex Desm. f. sp. tritici (Eriks.) CO Johnston (wheat brown rust), Mycosphaerella graminicola (Fuckel) Schroter (Septoria tritici Rob., leaf spot of wheat) and Magnaporthe grisea (Hebert) Barr (Pyricularia oryzae Cav., rice blast). Structure-activity relationship studies revealed the advantage of a fluoro substituent in position 6 and of a secondary amine in position 8. CONCLUSION 8-Amino-7-aryl-6-halogen-substituted pyrido[2,3-b]pyrazines have been prepared as 6,6-biheterocyclic analogues of similarly substituted triazolopyrimidine fungicides. A concise four-step synthesis route has been worked out to prepare these novel compounds from commercially available starting materials. [(R)-(1,2-Dimethylpropyl)]-[6-fluoro-7-(2,4,6-trifluorophenyl)pyrido[2,3-b]pyrazin-8-yl]amine showed excellent activity against three economically important phytopathogens.

Chemical crop protection research. Methods and challenges

Chemical crop protection, today a well-established technology to support sustainable production of food, feed, and fiber, will continue to play an important role in agribusiness in spite of the emergence of novel biotechnological solutions. Scientific progress in chemistry, biology, and molecular biology has revolutionized the way of searching for new agrochemicals over the past decade. Requirements, primarily in terms of safety to humans and the environment, have also changed. The search for and the development of novel agrochemicals with novel modes of action, improved safety profiles, and adapted to the changing requirement of the food and feed production chain are more than ever the challenge.

First preparative biocatalytic hydrolysis and S-methylation of cyclic trithiocarbonates

Abstract The biocatalytic degradation of a cyclic trithiocarbonate, 6-amino-5-methoxycarbonyl-thieno[2,3- d ]-1,3-dithiole-2-thione 1 , is reported. The product of the hydrolysis of the five-membered ring by Pseudomonas chlororaphis ATCC 9447 oxidatively dimerized to form the tetrathiocin derivative 2 . Furthermore, we performed the first preparative biocatalytic methylation of an unnatural compound employing Emericella unguis ATCC 10032 by cleaving the dithiole ring 1 followed by methylation of both thiol groups to form the methylated product 4 in 64% isolated yield.