New Nitrogen, Sulfur-, and Selenium-Donating Ligands Derived from Chiral Pyridine Amino Alcohols. Synthesis and Catalytic Activity in Asymmetric Allylic Alkylation.

Although many chiral ligands for asymmetric catalysis have been developed, there is still a need for new structures allowing the modular approach. Recently, easy synthesis of chiral pyridine-containing β-amino alcohols has been elaborated by opening respective epoxides with enantiomeric 1-phenylethylamine. This paper reports the synthetic transformation of β-amino alcohols into the new complexing pyridine-containing seleno- and thioethers.

New Advances in the Synthetic Application of Enantiomeric 1-Phenylethylamine (α-PEA): Privileged Chiral Inducer and Auxiliary.

New developments in the synthesis, resolution, and synthetic applications of chiral 1-phenylethylamine (α-PEA) reported in the last decade have been reviewed. In particular, improvements in the synthesis of α-PEA and its derivatives and chiral resolution, as well as their applications in the resolution of other compounds, were discussed. α-PEA was used as a chiral auxiliary in the diastereoselective synthesis of medicinal substances and natural products.

Regioselective and Stereodivergent Synthesis of Enantiomerically Pure -Diamines from Chiral β-Amino Alcohols with 2-Pyridyl and 6-(2,2'-Bipyridyl) Moieties.

In this report, we describe the synthetic elaboration of the easily available enantiomerically pure β-amino alcohols. Attempted direct substitution of the hydroxyl group by azido-functionality in the Mitsunobu reaction with hydrazoic acid was inefficient or led to a diastereomeric mixture. These outcomes resulted from the participation of aziridines.

Cinchona Alkaloids-Derivatives and Applications.

Major Cinchona alkaloids quinine, quinidine, cinchonine, and cinchonidine are available chiral natural compounds (chiral pool). Unlike many other natural products, these alkaloids are available in multiple diastereomeric forms which are separated on an industrial scale. The introduction discusses in short conformational equilibria, traditional separation scheme, biosynthesis, and de novo chemical syntheses.

Diastereoselective Corey-Chaykovsky 9-epoxymethylation of Cinchona alkaloids: access to chiral scaffolds with diverse functionalities.

Reaction of dimethylsulfonium methylide with Cinchona alkaloid ketones proceeds with complete diastereoselectivity to give epoxides of 8,9-like configuration. The reaction of dimethylsulfoxonium methylide gives different isomers, albeit with lower (4:1) selectivity. α-Epimerization of the alkaloid ketones resulted in formation of two separable diasteromeric products.

Monoimine derived from trans-1,2-diaminocyclohexane and ethyl glyoxylate: an intermediate in aza-Diels-Alder and Mannich reactions.

Novel enantiopure policyclic nitrogen heterocycles have been obtained in the diastereoselective aza-Diels-Alder or Mannich reaction of dienes with imine formed in situ from ethyl glyoxylate and (1R,2R)-diaminocyclohexane.

Enantioselective nitroaldol reaction catalyzed by sterically modified salen-chromium complexes.

A group of modified (salen)Cr(III)Cl complexes with bulky benzylic substituents in the 3,3'-position of the salicylidene moiety have been successfully applied for the asymmetric nitroaldol reaction. The readily accessible complex bearing 3-phenylpent-3-yl groups (2 mol %) leads to beta-nitro alcohols in up to 92% yield and 94% ee.

Stereoselective C9 carbon-carbon couplings of quinine: synthesis and conformational analysis of new C2-symmetric dimers.

An unexpected stereoselective direct dimerization occurred when 9-quinine halide was treated with butyllithium. The reaction of either (9S)- or (9R)-chloroquinine gave the same C2-symmetric dimer with 9R configuration (X-ray structure). A tentative mechanism involving radical recombination is discussed.

Stereoselective C9 arylation and vinylation of Cinchona alkaloids.

A simple and efficient method for the highly stereoselective C-9 arylation and vinylation of Cinchona alkaloids was developed. Both 9S- and 9R-chloroquinine with PhMgBr yielded 9S-phenylquinine (X-ray structure). The reactions with various aryl and vinyl Grignard reagents resulted in the series of 9S-aryl and vinyl alkaloid derivatives.