title: Organocatalytic asymmetric nitroaldol reaction: cooperative effects of guanidine and thiourea functional groups.
abstract: Catalytic enantio- and diastereoselective nitroaldol reactions were explored by using designed guanidine-thiourea bifunctional organocatalysts under mild and operationally simple biphasic conditions. These catalytic asymmetric reactions have a broad substrate generality with respect to the variety of aldehydes and nitroalkanes. Based on this catalytic nitroaldol process, straightforward syntheses of cytoxazone and 4-epi-cytoxazone were achieved. These catalytic nitroaldol reactions require KI as an additive for highly asymmetric induction; it operates by inhibiting the retro mode of the reaction. On the basis of studies of structure and catalytic-activity relationships, a plausible guanidine-thiourea cooperative mechanism and a transition state of the catalytic reactions are proposed. Drastic substituent effects on the catalytic properties of this catalyst may lead to the development of new chiral surfactants.
authors.affiliation: Graduate School of Pharmaceutical Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Sohtome
authors.forename: Nobuko
authors.initials: N
authors.lastname: Takemura
authors.forename: Keisuke
authors.initials: K
authors.lastname: Takada
authors.forename: Rika
authors.initials: R
authors.lastname: Takagi
authors.forename: Toshitsugu
authors.initials: T
authors.lastname: Iguchi
authors.forename: Kazuo
authors.initials: K
authors.lastname: Nagasawa
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D002853:Chromatography, Liquid; D019791:Guanidine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D013890:Thiourea / Q000737:chemistry*
chemical_list: D000447:Aldehydes; C116609:3-hydroxybutanal; D013890:Thiourea; D019791:Guanidine