An approach to the synthesis and resolution of five- and six-membered lactams (i.e., 5-oxopyrrolidine- and 6-oxopiperidine-3-carboxylic acids) is described. The method relies on the one-pot Michael reaction—cyclization of itaconic acid or diethyl homoitaconate and enantiopure O-(α-phenylethyl)hydroxylamine as a ‘chiral ammonia equivalent’. It is shown that this chiral auxiliary can be used for the separation of diastereomeric lactam products and then easily removed by catalytic hydrogenolysis.
The multi-component Betti reaction of 2-naphthol, benzaldehyde and (S)-amines, that usually provides highly valuable aminobenzylnaphthol bearing two stereogenic centers, yielded a completely racemic product, when (S)-valine methyl ester was employed as the amine in the usual reaction protocol. The cause of this drawback, that appears to be overlooked in the literature, was investigated. As a result, new reaction conditions were set up, that were able to yield the expected useful product, having two fully resolved stereogenic centers. Furthermore, when the effect of substituents on the phenyl ring was preliminarily studied, we found that 4-fluoro- and 4-chlorobenzaldeyde gave stereoisomerically pure compounds also in the original reaction protocol.
Iodoalkenes, such as 2-iodo-bornene, 17-iodoandrost-16-ene, 3-methoxy-17-iodoestra-1,3,5(10),16-ene, 3β-hydroxy-20-iodopregna-5,20-diene and 3β-hydroxy-12-iodo-5α,25R-spirost-11-ene were aminocarbonylated with enantiomerically pure and racemic α-phenylethylamine as the N-nucleophile in the presence of palladium(0) catalysts. Monodentate and bidentate (chiral and achiral) phosphines were used as ligands in the catalytic system. All diastereoisomers of the corresponding carboxamides were characterised as pure stereoisomers using both α-phenylethylamine and iodoalkene in enantiomerically pure form. The diastereoisomers were obtained in moderate to high yields in a chemoselective reaction, i.e., carboxamides due to single carbon monoxide insertion were formed exclusively, with no double CO insertion leading to 2-ketocarboxamides. Diastereoselectivities of the aminocarbonylation were investigated using the N-nucleophile in racemic form by the systematic variation of the catalyst.
The manuscript describes synthesis of new chiral organosilica networks starting from modified readily available enantiopure substances such as sugars and amino acids. We report on the successful preparation of robust all-chiral organosilicas by polymerization of the homochiral monomers. When the homochiral organosilane monomers were polymerized in mixtures of polar organic solvents and water in the presence of hydrochloric acid or tetrabutylammonium fluoride as catalysts, mainly spherical microparticles were obtained due to emulsification of the hydrophobic monomers in these mixtures. Polycondensation of the chiral organosilanes in the presence of Pluronic P123 as a template produced ordered mesoporous networks. The new all-chiral materials were characterized by SEM, STEM, BET, SAXS, IR, NMR and TGA.
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