Importance of chemical polymorphism in modern crop protection.

The development of agrochemical products faces many scientific challenges. After selection of an agrochemical candidate its properties will have to be optimized to guarantee best bioavailability and stability under many different conditions in various formulation types. These challenges are influenced by the solid-state properties of the active ingredient and this makes the selection of an optimized solid-state form of modern agrochemicals at early development stages very valuable. The increasing awareness of the solid state of agrochemicals is reflected in the importance of polymorphism patent applications, which may enhance the risk of litigations. This review aims to present strategies for the solid-form selection process of agrochemical development candidates. It introduces the different techniques for crystallization and analytics and demonstrates the influence of the solid state on different formulation types. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Artemisinin biosynthesis in growing plants of Artemisia annua. A 13CO2 study.

Artemisinin from Artemisia annua has become one of the most important drugs for malaria therapy. Its biosynthesis proceeds via amorpha-4,11-diene, but it is still unknown whether the isoprenoid precursors units are obtained by the mevalonate pathway or the more recently discovered non-mevalonate pathway. In order to address that question, a plant of A. annua was grown in an atmosphere containing 700 ppm of 13CO2 for 100 min. Following a chase period of 10 days, artemisinin was isolated and analyzed by 13C NMR spectroscopy. The isotopologue pattern shows that artemisinin was predominantly biosynthesized from (E,E)-farnesyl diphosphate (FPP) whose central isoprenoid unit had been obtained via the non-mevalonate pathway. The isotopologue data confirm the previously proposed mechanisms for the cyclization of (E,E)-FPP to amorphadiene and its oxidative conversion to artemisinin. They also support deprotonation of a terminal allyl cation intermediate as the final step in the enzymatic conversion of FPP to amorphadiene and show that either of the two methyl groups can undergo deprotonation.