Stereocontrol utilizing intermolecular interaction

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Dynamic control of intermolecular interaction is indispensable for achieving highly stereocontrolled reactions. We have developed various new stereocontrolled reactions on the basis of new knowledge on the factors controlling intermolecular reactions.(1) Study with metallosalen complexesThe X-ray structural analysis of metallosalen complexes clarified that conformation of the salen ligands is strongly influenced by weak-bond interactions such as OH-π and CH-π interactions and by the presence or absence of a donor ligand. With this knowledge, highly cis- and enantio-selective cyclopropanation was achieved for the first time. Furthermore, new type of asymmetric catalysts activated by photo-irradiation were introduced and, with these complexes, catalytic asymmetric oxidation using molecular oxygen as the terminal oxidant was developed.(2) New methodologies for acyclic stereocontrolStereospecific and regioselective epoxide-ring opening using new aluminum and borane reagents enabled efficie … More nt construction of consecutive asymmetric centers. High efficient construction of chiral quaternary carbons was also developed. With these reactions as key steps, various natural products of complex architectures were synthesized in a highly straightforward manner.(3) Asymmetric induction based on dynamic chirality of enolate structureDirect α-alkylation of optically active α-amino acids was achieved in an enantiospecific manner in the absence of any external chiral sources. Newly introduced nucleophylic catalyst bearing p-aminopyridine moiety enabled highly enantiomer-differentiating acylation. The origin for the observed selectivity was attributed to enantiomer-selective acceleration.(4) Transition metal catalysts in stereoselective carbohydrate synthesisVarious carbohydrate derivatives were synthesized efficiently from protected and unprotected glucals by using transition metal catalysts.(5) Desymmetrization of meso-diols and memory of chirality in carbenium ionAsymmetric desymmetrization of meso-diols was achieved efficiently by mono-acylation using chiral binaphthyltin dibromide as a catalyst. Optically acive α-amino acids were converted into optically active aminals via the corresponding acylinium ions in the absence of any external chiral sources. These results disclosed that memory of chirality can be observed in the reactions proceeding through a carbenium intermediate. Less