狩野 直和

We report conjugated methine compounds generated from N-arylpyridiniums and amines; streptocyanines can be used as a new activation mode for amine catalysis and applied to the conversion of pyridine rings to benzene rings.

Abstract Ligand coupling on sulfur, as an alternative to transition-metal-catalyzed cross-coupling reactions, is a useful method for connecting sp2 carbons. Although pioneered more than 50 years ago, its synthetic utility has been overlooked until recently. This short review summarizes progress in C(sp2)–C(sp2) bond formation using ligand coupling on sulfur and discusses control of selectivity, expansion of the scope, and applications of the reaction. 1 Introduction 2 Cross-Coupling of Heteroaryl Reagents 3 Phenothiazinium-Mediated C(sp2)–C(sp2) Cross-Coupling 4 C(sp2)–C(sp2) Bond Formation Mediated by Sulfuranes Generated from Arynes and Sulfoxides 5 S-Alkenylbenzothiophenium-Mediated Alkenyl-Alkenyl Coupling 6 Conclusion

Trifluoromethylated thermally activated delayed fluorescent molecule 4[Cz(CF₃)₂]IPN has been demonstrated as a versatile photocatalyst that facilitates radical reactions via electron transfer and dearomative cycloaddition via energy transfer.

Enzymes involved in the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs) often have relaxed specificity profiles and are able to modify diverse substrates. When several such enzymes act together during precursor peptide maturation, a multitude of products can form, yet usually the biosynthesis converges on a single natural product. For the most part, the mechanisms controlling the integrity of RiPP assembly remain elusive. Here, we investigate the biosynthesis of lactazole A, a model thiopeptide produced by five promiscuous enzymes from a ribosomal precursor peptide. Using our in vitro thiopeptide production (FIT-Laz) system, we determine the order of biosynthetic events at the individual modification level and supplement this study with substrate scope analysis for participating enzymes. Our results reveal an unusual but well-defined assembly process where cyclodehydration, dehydroalanine formation, and azoline dehydrogenation events are intertwined due to minimal substrate recognition requirements characteristic of every lactazole enzyme. Additionally, each enzyme plays a role in directing LazBF-mediated dehydroalanine formation, which emerges as the central theme of the assembly process. Cyclodehydratase LazDE discriminates a single serine residue for azoline formation, leaving the remaining five as potential dehydratase substrates. Pyridine synthase LazC exerts kinetic control over LazBF to prevent the formation of overdehydrated thiopeptides, whereas the coupling of dehydrogenation to dehydroalanine installation impedes generation of underdehydrated products. Altogether, our results indicate that substrate-level cooperation between the biosynthetic enzymes maintains the integrity of lactazole assembly. This work advances our understanding of RiPP biosynthesis processes and facilitates thiopeptide bioengineering.

<p>Aryllithiums were arylated with <italic>S</italic>-arylphenothiazinium ions through selective ligand coupling of intermediary sulfuranes. Various unsymmetrical biaryls were obtained without transition-metal catalysis.</p>