title: Construction of Vicinal Quaternary Stereogenic Centers by Enantioselective Direct Mannich-Type Reaction Using a Chiral Bis(guanidino)iminophosphorane Catalyst.
abstract: A novel asymmetric direct Mannich-type reaction of α-iminophenylacetate esters with thionolactones, bearing a substituent at the α-position, as a less acidic pronucleophile was developed. Using bis(guanidino)iminophosphorane as the chiral organosuperbase catalyst, the reaction afforded densely functionalized amino-acid derivatives having vicinal quaternary stereogenic centers, one of which is an all-carbon quaternary stereogenic center, in good yield with high diastereo- and enantioselectivities.
authors.affiliation: Process Technology Research Laboratories, Daiichi Sankyo Co., Ltd., Edogawa-ku, Tokyo, 134-8630, Japan.
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Takeda
authors.affiliation: Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan.
authors.forename: Azusa
authors.initials: A
authors.lastname: Kondoh
authors.affiliation: Research and Analytical Center for Giant Molecules, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan. mterada@m.tohoku.ac.jp.|Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan. mterada@m.tohoku.ac.jp.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Terada
keywords: acidity; asymmetric catalysis; heterocycles; organocatalysis; phosphazene