Asymmetric organocatalysis mediated by primary amines derived from cinchona alkaloids: recent advances

Monomeric and Dimeric 9‐O Anthraquinone and Phenanthryl Derivatives of Cinchona Alkaloids as Chiral Solvating Agents for the NMR Enantiodiscrimination of Chiral Hemiesters

“…With the plan of carrying out chiral discrimination measurements also in a solvent less expensive than toluene-d 8 (vide infra), at the outset of the present study the conformational characterization of 1 was repeated in CDCl 3 . Even though extensive signal superimposition was found under these conditions, a selective H1-H10 dipolar interaction could be detected, which is diagnostic for the Open(3) conformation.…”

“…On the contrary, the same bonds are cisoid (dihedral angle H8-C9-C8-H9 about of 78°) in Open-like conformations, making the basic quinuclidine nitrogen better predisposed for the interaction with suitable hydrogen bond donor groups. Inside each family of conformations (Closed or Open), rotation about the C9-C16 bond is possible, leading the C9-H8 bond bent at the H1 quinoline proton in Closed (1) or Open(4) or at its H5 proton Closed (2) or Open (3). The values of the vicinal coupling constant 3 J H8-H9 and through space dipolar interactions allow the definition of the conformational preference, which is strongly affected by the nature of any derivatizing group at the hydroxyl function or quinuclidine nitrogen and is often remarkably dependent on the solvent.…”

“…Applications of cinchona alkaloids as chiral auxiliaries in organic chemistry date back to late 1853, 1 with their use as resolving agents. Since then a great number of applications could be found spanning from asymmetric synthesis and catalysis, [2][3][4][5][6][7] to chromatographic [7][8][9] and spectroscopic enantioseparations. 10,11 Cinchona alkaloids enantiodifferentiating ability may be ascribed to their highly preorganized structure, which makes several interaction sites available for the stabilization of supramolecular aggregates with different classes of enantiomeric substrates.…”

β- and σ-Amino acids (2,3- and 3,4-trans-CHA) as catalysts in Knoevenagel condensation and asymmetric aldol reactions

“…[19][20][21] The use of primary amino acids as chiral catalysts has been thoroughly studied and improved within the past decade. [22][23][24][25] In 2005, Amedjkouh reported the L-valine-catalyzed intermolecular aldol addition of acetone with aromatic aldehydes; sufficient yields and enantiomeric excesses were achieved. 26 Other natural primary amino acids were also used.…”

The Synthesis of New Spirolactones from Substituted Isatins

“…Such developments are of interest not only for the possible total synthesis of therapeutically useful spirooxindoles [6][7][8][9][10][11][12][13][14][15], but also for the preparation of synthetic analogs [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] in order to improve our knowledge in structure-activity relationships [12-14, 31, 32]. So-called butenolide functionalized spirooxindoles 1 provide the most interesting subject for synthetic investigations in view of the large and ever increasing number of the members of this family which have furan-2(5H)-one 2 as a building block (Scheme 1).…”