Developments of Novel Synthetic Reactions under High Pressure Conditions

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(a) Diels-Alder Reaction of Resin Acids : Novel Diels-Alder reaction of methyl palustrate with maleic anhydride and N-phenylmaleimide has been established under high pressure conditions.(b) Synthetic Study of AI-77-B : High pressure approach to construct the amide bond between a dihydroisocoumarin and a hydroxyamino acid part of AI-77-B has been investigated. Thus, as a model reaction, the N-Boc lactam derivative prepared from D-ribose was efficiently condensed with cyclohexylamine at 10 kbar pressure without using any catalysis.(c) Aminolysis of Epoxides with Glycine Esters : Uncatalyzed aminolysis of epoxides with glycine esters has been efficiently performed under high pressure conditions. In connection with this study, we found that silica gel acted as a powerful solid acid catalyst for this type of epoxide opening reaction.(d) Reaction of Epoxides with Nitrogen Heterocycles : The reaction of epoxides with nitrogen heterocycles such as indoles, pyrroles, and pyrazoles has been perf … More ormed under high pressure-promoted or silica gel-catalyzed conditions. The stereochemical feature for an epoxide opening reaction with indole has been proposed as having a concerted S_N2 mechanism.(e) Synthetic Design of Novel Chiral Ligands : High pressure reaction of chiral epoxides with pyrazoles provided novel procedure to obtain chiral diazole ligands. These ligands were successfully applied for an enantioselective alkylation of benzaldehyde with diethylzinc.(f) Synthesis of Diolmycin A2 : A new short synthesis of diolmycin A2 has been performed by using high pressure-promoted epoxide opening reaction with indole as a key step.(g) Transformation of epoxides to the Corresponding Halohydrins : A variety of epoxides have been efficiently converted into the corresponding halohydrins by treatment with silica gel-supported lithium halides in dry media.(h) Functionalization of Silica Gel under High Pressure Conditions : As a final project to use high pressurt chemistry, a new method to functionalize silica gel with chiral substances has been developed and its utility for HPLC analysis has been also demonstrated. Less