Biomimetic Diels-Alder Reactions in Natural Product Synthesis: A Personal Retrospect

Total Synthesis of Carolacton and Demethylcarolactons with Potent Antiviral Activity

Carolacton, a naturally occurring MTHFD1 inhibitor, exhibits potent inhibitory activity against various RNA viruses including SARS-CoV-2. Herein, we present a concise total synthesis of carolacton, featuring the Krische allylation, Marshall coupling, NHK coupling, and RCM reaction as key elements. Additionally, we have synthesized three simplified carolacton analogues, one of which, namely, 14-demethyl-carolacton, exhibited notable antiviral activity. The present work paves the way for further exploration of the therapeutic potential of carolacton and its analogues.

Aza-Povarov Reaction. A Method for the Synthesis of Fused Tetracyclic Chromeno[4,3-d]pyrido[1,2-a]pyrimidines

A cornerstone in drug discovery is the development of strategies to provide privileged small molecules with specific structural and stereochemical complexity, allowing access to new potential therapeutic entities. In this work, a new strategy based on the [4 + 2] Povarov reaction involving 1,3-diazadiene was developed. This approach is applied for a straightforward procedure in the preparation of chromeno[4,3-d]pyrido[1,2-a]pyrimidine derivatives, with accessible substrates, 2-aminopyridine and unsaturated aldehydes, and excellent atom economy to obtain four fused ring heterocycles, in a regio- and diastereoselective way.

Elucidation of the stereocontrol mechanisms of the chemical and biosynthetic intramolecular Diels-Alder cycloaddition for the formation of bioactive decalins

The intramolecular Diels-Alder reaction (IMDA) is a powerful method for regioselective and stereoselective construction of functionalised decalin skeletons, and the recent discovery of enzymes that catalyse IMDA cycloaddition in biosynthesis has generated considerable interest. This study focused on the role of the absolute configuration of the C-6 carbon of the substrate polyene in the stereocontrol of the IMDA reaction catalysed by Fsa2 and Phm7, which construct different enantiomeric decalin skeletons. Their enantiomeric precursor polyenes were synthesised and subjected to enzymatic or thermal IMDA reactions to isolate various diastereomeric decalines and determine their absolute configuration. Furthermore, density functional theory calculations were performed to elucidate the stereocontrol mechanism underlying the formation of decalin. The results showed that Fsa2 exhibits the same equisetin-type stereoselectivity for enantiomeric substrates regardless of the 6-methyl group configuration of the substrate, while Phm7 shows two types of stereoselectivity depending on the configuration of the 6-methyl group. We also found a unique stereochemistry-activity relationship in antibacterial activity for decalin diastereomers, including new derivatives. This study provides new insights into the stereoselectivity of DAase, which is important in the synthesis of natural product skeletons.

Cluster Preface: Development and Applications of Novel Ligands/Catalysts and Mechanistic Studies on Catalysis

Zhipeng Zhang (left) received his B.S. degree from Shandong University (China) in 2004, and his Ph.D. degree from the Shanghai Institute of Organic Chemistry (SIOC) in 2010 under the supervision of Professor Kuiling Ding. In 2011, he began his postdoctoral studies with Professor Benjamin List at the Max Planck Institute for Coal Research in Mülheim an der Ruhr, Germany. After three years of research on asymmetric organocatalysis, he joined the group of Professor Jin-Quan Yu at The Scripps Research Institute in La Jolla, California as a postdoctoral research associate in 2014. He subsequently worked at the Genomics Institute of the Novartis Research Foundation (GNF) from 2016, before he began his independent career as a professor at the East China University of Science and Technology (ECUST) in 2017. His current research interests include asymmetric catalysis and synthetic methodology, focusing on the design and development of novel chiral ligands and catalysts.

Baoguo Zhao (right) received his B.S. degree from Wuhan University in 1996, his M.S. degree from Nanjing University under the supervision of Professor Jianhua Xu in 2002, and his Ph.D. degree from the Shanghai Institute of Organic Chemistry (SIOC) under the supervision of Professor Kuiling Ding in 2006. He subsequently worked with Professor Yian Shi for five years as a postdoctoral fellow at the Department of Chemistry of Colorado State University. In 2011, he joined Shanghai Normal University at the Department of Chemistry as a full professor. His current research interests are in the area of biomimetic asymmetric catalysis, including the development of bioinspired chiral catalysts and synthetic methodologies.

Gram-Scale Enantioselective Synthesis of (+)-Lucidumone

The first enantioselective total synthesis of (+)-lucidumone is described through a 13-step synthetic pathway (longest linear sequence). The key steps involve the formation of a bridged bicyclic lactone by an enantioselective inverse-electron-demand Diels-Alder cycloaddition, C-O bond formation to assemble two fragments, and a one-pot retro-[4 + 2]/[4 + 2] cycloaddition cascade. The synthesis is scalable, and more than one gram of natural product was synthesized in one batch.