Keiichi Sorimachi

Enantioselective direct aldol-type reaction of azlactone via protonation of vinyl ethers by a chiral Brønsted acid catalyst.

Highly enantio- and diastereoselective direct aldol-type reaction of azlactones with oxocarbenium ions generated by protonation of vinyl ethers using a chiral phosphoric acid catalyst is presented. The method provides efficient access to biologically and pharmaceutically intriguing beta-hydroxy-alpha-amino acid derivatives having a quaternary stereogenic center at the alpha-carbon atom.

Relay Catalysis by a Metal-Complex/Brønsted Acid Binary System in a Tandem Isomerization/Carbon−Carbon Bond Forming Sequence

A one-pot tandem isomerization/carbon-carbon bond forming sequence catalyzed by a ruthenium complex/Brønsted acid binary system is demonstrated. The method enables the use of readily available allylamides to deliver reactive imines under relay catalysis using a binary catalytic system. Subsequent Brønsted acid catalyzed carbon-carbon bond forming reactions of the generated imines with nucleophilic components afforded Friedel-Crafts and Mannich products in good yields.

Activation of Hemiaminal Ethers by Chiral Brønsted Acids for Facile Access to Enantioselective Two-Carbon Homologation Using Enecarbamates†

An enriching experience: Chiral phosphoric acids have been used to catalyze the title transformation for aromatic and aliphatic hemiaminal ethers. The process affords the corresponding products in good to high enantioselectivity (see scheme; Boc = tert-butoxycarbonyl, G = aromatic group). The method enables facile access to highly enantioenriched 1,3-diamine derivatives.

Chiral Brønsted Acid Catalyzed Stereoselective Addition of Azlactones to 3-Vinylindoles for Facile Access to Enantioenriched Tryptophan Derivatives**

Syn-gled out: The syn diastereo- and enantioselective addition of azlactones to 3-vinylindoles was accomplished by using a chiral, binapthol-derived, Brønsted acid catalyst (see scheme). This method enables facile access to tryptophan derivatives with adjacent quaternary and tertiary stereogenic centers, which are potentially useful for the synthesis of peptidomimetics.