The first synthetic example of phosphoric acids with a binaphthyl group appeared in 1971. Since then, their use as chiral molecular tools slowly increased. In contrast, the reports in 2004 that those acids with 3,3’-disubstituted binaphthyl groups catalyzed Mannich-type asymmetric reactions dramatically facilitated the development of catalytic reactions with those acids as chiral Brønsted acids. One simple idea to design isologues of those acids was the replacement of the oxygen atom of P=O and P-O groups with heavier elements in the Periodic Table. In fact, some isologues with a P=S bond appeared, but no derivatives with a P=Se bond were seen in 2001. We then started to develop the synthetic chemistry of selenium isologues of phosphoric acid derivatives with a binaphthyl group. The accidental finding of the formation of phosphoroselenoyl chlorides with a binaphthyl group stimulated our studies, and we developed a range of the derivatives with oxygen-, nitrogen-, and carbon-containing substituents on the phosphorus atom. Some of them can be used as a chiral discriminating agent, key starting materials to optically active alcohols, diselenides, organophosphorus compounds with a chiral carbon atom adjacent to the phosphorus atom, optically active trivalent organophosphorus compounds. During our studies, we also found the reaction involving the transfer of the axial chirality of a binaphthyl group to the central chirality of the phosphorus atom.

Glycans, considered as the third life chain following nucleic acids and proteins, are involved in various biological phenomena, including signal transduction, immune regulation, infection, aging, and cancer. However, the synthesis of glycans with complex and diverse structures has not been established, and thereby, the glycan functions have not been well elucidated at the molecular level. Small glycan fragments, such as monosaccharides and disaccharides, can exhibit biological activities through interactions with their recognition proteins (lectins). On the other hand, complex structures of glycans show emergent functions via multivalent recognition, conformational control and so on. Furthermore, glycans cover the cell surface as a glycocalyx, and form dynamic and flexible interaction networks with various biomolecules to realize complicated regulation of biological phenomena. We have been exploring such higher-order glycan functions by chemical biology approach based on organic synthesis. Namely, we have synthesized complex glycans and glycoconjugates, and these synthesized compounds were utilized for analyzing and regulating glycan functions.

In the recent two decades, stimuli-responsive photoluminescent (PL) solid materials have attracted much attention because their materials can dramatically change luminescent colors in response to external stimuli. However, applications used by organic solid materials are limited to luminescent colors only. Designs and fabrications of materials outputting changes in physical properties other than PL properties can expand application scenes and options as well as create novel material designs instead of solid materials. In this article, we describe developments of stimuli-responsive photoluminescent liquid materials by a synergy between experimental and theoretical investigations. Room-temperature liquid material is promising as an organic solvent free material with a low environmental load. Moreover, a fluidic property of liquid can retain the high-process reproducibility of coating film without formations of defects and grain boundaries by anyone, anytime, and anywhere. In this article, material designs of stimuli-responsive PL liquids are very easy, of which liquids can show dramatic changes in multiple physical properties by a single stimulus only, as not observed for solid materials. Stimuli-responsive PL liquids can show liquid-solid (disorder-order) phase transition in response to external stimuli at a micro-scale level. The elucidation of these behaviors can be predicted by experimental methods, but only speculation. Theoretical methods have helped us out of five miles in the fog, which can elucidate this stimuli-responsive behavior at a molecular level. These results are almost consistent with those predicted by experimental ones and disorder-order phase transition can be clearly elucidated over multiscale. Moreover, novel stimuli-responsive liquids designed based on theoretical results can show desired functions in experiments. These results prove the synergy between experimental and theoretical methods opens a new strategy to develop stimuli-responsive liquid materials with desired functionalities.

Oxygen-containing ring structure is one of the characteristic substructures found in many natural organic compounds. Among them, a lot of natural products with ether ring structures have been reported to exhibit noteworthy and potentially useful biological activities, attracting much attention from natural product chemists and medicinal chemists. In addition, oxacyclic natural products listed as lead candidate compounds for pharmaceuticals often have unique chemical structures, which have been the attractive targets for extensive studies on their total synthesis by synthetic organic chemists. Although, needless to say, the shortness of the total reaction steps is the primary target of pursuit, in general, steric control of chiral centers as well as geometry is also an important issue for the efficient synthesis of complex natural products. The authors, in this research, have taken up amphirionin-4, anthecularin, and celafolin B1, B2, and B3, ether ring-containing natural products that exhibit remarkable biological activities, as synthetic targets, and have conducted synthetic studies toward their total syntheses with a particular focus on stereoselective construction of chiral centers. As a result, the authors found out stereospecific reactions based on the three-dimensional characteristics of certain synthetic intermediates, which abled construction of efficient and scalable synthetic routes. In this paper, the details of our synthetic studies on the asymmetric total syntheses of amphirionin-4, anthecularin, isocelorbicol, and celafolin B1, B2, and B3 are described.

Polycyclic structures are found in many natural products and pharmaceuticals. The transition-metal-catalyzed cycloisomerization of unsaturated compounds is one of the most powerful methods for construction of polycyclic frameworks in a single operation. In particular, 1,6-diyne is the structural motif widely used for the cycloisomerization as it readily reacts with low-valent metal catalysts to form metallacyclopentadiene intermediates. However, this method has been mainly exploited for the synthesis of aromatic compounds such as benzenes and pyridines. This article describes our recent studies regarding the synthesis of various polycyclic structures including non-aromatic carbocycles, such as 5-6-5 tricyclic cyclohexadienes bearing a quaternary bridgehead carbon and tetralone-containing exocyclic dienes, via the group 9 metal-catalyzed cycloisomerization reaction of 1,6-diyne derivatives. In the course of our study, we elucidated that the cobalt/photoredox dual catalysis is very efficient for the cycloisomerization of 1,6-diyne derivatives such as enediynes. We also found a novel cascade cyclization of 1,6-diynyl esters to form various cyclic compounds through the formation of vinylallene intermediates.

The direct modification of molecular skeletons through single-atom manipulation is complementary to peripheral modifications (i.e., C-H functionalization) and is of particular significance. This short review describes the recent advances in the development of ring-expansion reactions by single-atom skeletal editing.