C2-symmetric Derivatives Research Articles

Catalytic Enantioselective Construction of Decalin Derivatives by Dynamic Kinetic Desymmetrization of C2-Symmetric Derivatives through Aldol-Aldol Annulation.

We have developed and investigated a catalytic desymmetrization reaction strategy that affords functionalized decalin derivatives with high enantioselectivities from C2-symmetric derivatives through aldol-aldol annulation. We identified the structural moieties of the catalyst necessary for the formation of the decalin derivative with high enantioselectivity. We elucidated the mechanisms of the catalyzed reactions: the first aldol reaction step was reversible, and the second aldol step was rate-limiting and stereochemistry-determining and was enantioselective. Using theoretical calculations guided by the experimental results, we identified the interactions between the catalyst and the transition state that led to the major enantiomer. The information obtained in this study will be useful for the development of catalysts and chemical transformations.

Synthesis, Chemical Properties, and Biological Evaluations of Some Twin-Drug Type C2-Symmetrical Derivatives

Synthesis, Chemical Properties, and Biological Evaluations of Some Twin-Drug Type C2-Symmetrical Derivatives

Preparation and Properties of C 2-Symmetric Organic Radical Compounds Showing Ferroelectric Liquid Crystal Properties

We have synthesized a new class of liquid crystalline (LC) organic radical compounds 2, which are the C2-symmetric derivatives of the previously reported compounds 1 containing a chiral nitroxide unit and an ester group in the mesogen core, and their LC properties have been fully characterized. The enantiomerically enriched 2 showed N* and SmC* phases. Their LC phase transition behavior is similar to that of 1, whereas the ferroelectric properties of the SmC* phase of (2S,5S)-2 differed from those of (2S,5S)-1. We discuss the origin of this difference in terms of their molecular structures optimized by molecular orbital calculations.

Spacer-Mediated Synthesis of Contra-Thermodynamic Spiroacetals: Stereoselective Synthesis of C2-Symmetric Difructose Dianhydrides

The xylylene moiety (ortho, meta, and para) was employed as a rigid tether in the spacer-mediated synthesis of difructose dianhydrides (DFAs), a unique class of bis-spiroacetal derivatives present in food products. The synthetic methodology exploits the suitability of triflic acid to promote spirocyclization in organic solvents under irreversible reaction conditions, using anomeric isopropylidene fructose derivatives as precursors. Advantage was taken of the strong dependence of the conformational properties of DFAs on the relative configuration of the spiroketal centers. Highly stereoselective syntheses of the contra-thermodynamic difructofuranose and difructopyranose diastereomers, namely the C2-symmetric derivatives having the beta-configuration at both anomeric centers, have been accomplished by judicious choice of the xylylene positional isomer and of the linking position to the fructose building blocks. Interestingly, the rigid spacer concept has also been implemented to favor intermolecular processes leading to higher macrocyclic architectures that incorporate the bis-spiro fructodisaccharide subunit.

Synthesis and anti-HIV activity of new C2 symmetric derivatives designed as HIV-1 protease inhibitors

The synthesis of several new anti-HIV-1 compounds is described. The new compounds contain a C 2 symmetry axis and a dihidroxyethylene moiety based on the d-tartaric acid back bone. The synthesis of these compounds was achieved in 36–69% overall yields from d-tartaric acid. The protocol included: acetylation of hydroxyl groups, followed by diamide formation and deacetylation or reduction with LiAlH 4. The anti-HIV 1 activities of these substances were evaluated in PM-1 cells, using Indinavir® as standard (IC 50=0.2 μM). Two amino alcohol derivatives showed good inhibitory activity against the virus, with IC 50=2.0 and 4 μM.

The synthesis of C2-symmetric 1,4,7-triazacyclononane ligands derived from chiral aziridines

An efficient synthetic route for the synthesis of C2-symmetric derivatives of 1,4,7-triazacyclononanes 14 from chiral pool amino acids has been developed. These investigations have shown that competitive formation of piperazines 7 occurs when inappropriate nitrogen protecting groups are employed. It is apparent that the formation of the piperazines occurs as a result of an intramolecular nucleophilic attack followed by a β-elimination. This appears to only be relevant for the formation of the [9]-N3 ring, as the larger [12]-N4 macrocycle, 11, is formed via a Richman–Atkins cyclisation in the presence of the same benzylic protected nitrogen atom. The single crystal X-ray structures of piperazine 7a and 1,4,7-triazacyclononanes 14a both reveal that weak intermolecular C–H⋯OS interactions occur in the solid state in these systems.