Enantioseparation of benzazoles and benzanilides on polysaccharide-based chiral columns.

The chiral recognition ability of the polysaccharide-based chiral columns (Chiralpak AD-RH, Chiralpak AS-RJ, Chiralpak IC, Chiralcel OD-RH, and Chiralcel OJ-RH) for the benzazoles and the benzanilides was evaluated under reversed phase conditions. The columns showed the high chiral recognition ability for a wide range of benzazoles and benzanilides. Twenty-one racemates were used for the evaluation, and 20 racemates were completely separated on at least one of the columns.

Microscale HPLC enables a new paradigm for commercialization of complex chiral stationary phases.

The small column size (0.3 mm i.d.

High-performance liquid chromatographic enantioseparations on capillary columns containing crosslinked polysaccharide phenylcarbamate derivatives attached to monolithic silica.

Monolithic capillary columns containing native silica gel were covalently modified with 3,5-disubstituted phenylcarbamate derivatives of cellulose and amylose and applied for enantioseparations in capillary LC. The method previously used for covalent immobilization of polysaccharide phenylcarbamate derivatives onto the surface of microparticulate silica gel was successfully adapted for in situ modification of monolithic fused-silica capillary columns. The effects of the nature of polysaccharide and the substituents, as well as of multiple covalent immobilization of polysaccharide derivative on chromatographic performance of capillary columns were studied.

Topologically chiral covalent assemblies of molecular knots with linear, branched, and cyclic architectures.

Selectively functionalized molecular knots (knotanes) of the amide-type have been used as building blocks in syntheses of higher covalent assemblies composed of up to four knotane units. Preparation of linear and branched tetraknotanes consisted of the consecutive selective removal of allyl groups followed by linking of the intermediate hydroxyknotanes with biphenyl-4,4'-disulfonyl chloride. Macrocyclic knotane oligomers involving two, three, and four knotane moieties were obtained by high-dilution cyclization of dihydroxyknotane and biphenyl-4,4'-disulfonyl chloride.

Reversed-phase liquid chromatographic enantioseparation by cycloalkylcarboxylates of cellulose and amylose.

Three novel cycloalkylcarboxylates, cyclopentyl, cyclohexyl, and 1-adamantylcarboxylates of cellulose and amylose were prepared and their chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were evaluated using a methanol-water mobile phase. Among these esters, cellulose tris(cyclohexylcarboxylate) showed a relatively high chiral recognition ability. The 1-adamantylcarboxylates of cellulose and amylose showed dissimilar chiral recognition abilities from the other two, probably due to the low degree of substitution and the high hydrophobicity of this group.

Preparation of chiral stationary phase for HPLC based on immobilization of cellulose 3,5-dimethylphenylcarbamate derivatives on silica gel.

The immobilization of cellulose 3,5-dimethylphenylcarbamate derivatives having a polymerizable vinyl group, i.e., 4-vinylphenylcarbamate or 2-methacyloyloxyethylcarbamate, on silica gel was examined under various conditions.

Dendronized molecular knots: selective synthesis of various generations, enantiomer separation, circular dichroism.

For the first time, knot molecules (of the amide type) are synthesized, which bear one to three dendritic units of various generations at their periphery. They were obtained through two different routes: i) attachment of dendritic wedges to new mono-, di- and trihydroxy functionalized dodecaamide knots that have been obtained by selective debenzylation of oligobenzyloxy substituted knots, or ii) cyclization of already dendron substituted pyridine-2,6-dicarbonyl dichlorides with an "extended diamine" to directly yield the "tri-dendroknots". The derivatization of knot molecules by functional substituents and even large dendritic units is an important advance in the synthesis and property variation of molecular knots.

Chromatographic enantioseparation by cycloalkylcarbamate derivatives of cellulose and amylose.

Cyclopentyl and (+/-)-exo-2-norbornylcarbamates of cellulose and amylose were prepared and their chiral recognition abilities as chiral stationary phases for high-performance liquid chromatography (HPLC) were evaluated. Among these carbamates, cellulose tris(cyclopentylcarbamate) and amylose tris((+/-)-exo-2-norbornylcarbamate) showed particularly high chiral recognition, which is comparable to that of several well-known phenylcarbamate derivatives. The chiral recognition mechanism of cellulose tris(cyclohexylcarbamate), which was previously found to be an effective chiral stationary phase for HPLC, was investigated using NMR spectroscopy.

Novel Amide-Based Molecular Knots: Complete Enantiomeric Separation, Chiroptical Properties, and Absolute Configuration.

By comparison of experimental and theoretical CD curves the absolute configurations of chromatographically baseline-separated enantiomers of new trefoil molecular knots could be determined. From the results of syntheses with differently substituted starting materials, conclusions can be drawn about the knot-formation mechanism.