10.1021/acs.orglett.1c00206
The study investigates the enzymatic basis for quinine biosynthesis, focusing on the early and late steps of the pathway. Quinine, an alkaloid produced by Cinchona trees, is historically used as an antimalarial drug and as a flavor ingredient in beverages. The researchers combined metabolomics and transcriptomics data from different tissues of Cinchona pubescens to identify genes involved in quinine biosynthesis. They discovered three key enzymes: a medium-chain alcohol dehydrogenase (CpDCS), an esterase (CpDCE), and an O-methyltransferase (CpOMT1). CpDCS and CpDCE were involved in converting strictosidine aglycone to dihydrocorynantheal, an intermediate in quinine biosynthesis, through reduction and esterase-triggered decarboxylation. CpOMT1 was found to specifically act on 6′-hydroxycinchoninone, suggesting a preferred order for the late steps of quinine biosynthesis. The chemicals used in the study included strictosidine, corynantheine aldehyde, dihydrocorynantheine aldehyde, and cinchoninone, among others, which served as substrates, intermediates, and products in the biosynthetic pathway of quinine. The purpose of these chemicals was to elucidate the enzymatic steps and intermediates involved in the biosynthesis of quinine, providing insights into the metabolic pathways and potential for synthetic biology applications in quinine production.
10.1021/acs.orglett.8b01085
The study presents a metal-free photoredox C?H alkylation of heteroaromatics using hypervalent iodine dicarboxylates and an organic photocatalyst, 9-mesityl-10-methyl acridinium (MesAcr), under blue LED light. The method leverages readily available carboxylic acids as coupling partners and operates under mild conditions at room temperature. Key chemicals include bis(trifluoroacetoxy)iodobenzene (PIFA) as the oxidant, which helps avoid complications from forming undesired alkylated products and eliminates the need for additional trifluoroacetic acid. The study explores the scope of various carboxylic acids, which generate different alkyl radicals (primary, secondary, tertiary) under the reaction conditions, and tests a range of heteroaromatics and complex molecules, including drugs like voriconazole, varenicline, and quinine, demonstrating good functional group tolerance. Mechanistic investigations, including control experiments, photophysical studies, and DFT calculations, suggest a distinct reaction mechanism involving a chain reaction with a low quantum yield, likely due to an inefficient initiation step.