title: Construction of contiguous tetrasubstituted chiral carbon stereocenters via direct catalytic asymmetric aldol and Mannich-type reactions.
abstract: Catalytic asymmetric synthesis of unnatural amino acids with vicinal tetrasubstituted chiral carbon stereocenters is described. In the first part, direct catalytic asymmetric aldol reaction of simple non-activated ketone electrophiles with α-substituted α-isothiocyanato ester donors was realized. A Mg/Schiff base catalyst promoted the aldol reaction, and α-amino-β-hydroxy esters were obtained in up to 98% ee and 98:2 d.r. In the second part, the Mg/Schiff base catalyst and a Sr/Schiff base catalyst were utilized for stereodivergent direct asymmetric Mannich-type reaction of ketimines. The Mg/Schiff base catalyst gave syn-α,β-diamino esters, while the Sr/Schiff base catalyst produced anti-α,β-diamino esters in good to high enantioselectivity, up to 97% ee.
authors: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo, Tokyo 113-0033, Japan. smatsuna@mol.f.u-tokyo.ac.jp
authors: Shigeki
authors: S
authors: Matsunaga
authors: Tatsuhiko
authors: T
authors: Yoshino
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000596:Amino Acids / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D004952:Esters / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry*; D012545:Schiff Bases / Q000737:chemistry
chemical_list: D000447:Aldehydes; D000596:Amino Acids; D004952:Esters; D007659:Ketones; D009942:Organometallic Compounds; D012545:Schiff Bases; D008274:Magnesium