Enantiospecific access to 10-N-substituted camphors

A general and straightforward enantiospecific access to synthetically valuable 10-N-substituted camphors (amines and secondary amides) has been developed. The synthetic method uses camphor as the starting enantiopure material and takes place in five individual steps with a high overall yield. The process involves a stereocontrolled double-Wagner-Meerwein-rearrangement strategy to generate key-intermediate 10-(triflyloxy)camphor, a peculiar and highly-reactive primary triflate, which is able to alkylate soft N-nucleophiles, such as amines and nitriles, easily and without producing Grob-like fragmentation of the β-(triflyloxy)ketone-based norbornane system.     

Effect of Chiral Additives in the Preparation of Cellulose-Based Chiral Stationary Phases in HPLC, and Effect on Enantiomer Resolution

Chiral stationary phases (CSPs) for high-performance liquid chromatographic (HPLC) have been prepared by coating silica gel with cellulose tribenzoate or cellulose trisphenylcarbamate. The effect of chiral additives on preparation of the CSPs was studied with (+)-l-mandelic acid, (−)-2-phenyl-1-propanol, (+)-1-phenyl-1,2-ethanediol and (−)-1-(1-naphthyl)ethanol as chiral additives for cellulose tribenzoate and (−)-2-phenyl-1-propanol and (+)-phenylsuccinic acid as chiral additives for cellulose trisphenylcarbamate. The results showed that chiral recognition by these stationary phases was increased in comparison with the original CSPs, especially the resolution (R _S) obtained. The method can be used to improve the efficiency of enantiomer separation by silica gel stationary phases coated with polymers.     

Application of the ERAS-Model to binary mixtures of diethylamine and s-butylamine with acetonitrile in the temperature range (288.15–303.15) K

Densities for binary mixtures of diethylamine and s-butylamine with acetonitrile have been measured at 288.15, 293.15, 298.15 and 303.15 K using a vibrating-tube densimeter. Excess molar volumes (V_m^E) were determined. Both systems exhibit negative V_m^E values over the entire composition range in the temperature range studied. ERAS-Model calculations allowing for self-association for the amines and complex formation between acetonitrile and amines were performed. The agreement between theoretical and experimental results is satisfactory only for mole fractions of amines less than 0.50. A simplified version of the model, without the chemical contribution, gives similar results.     

(R)-TTCA·K催化下环己酮与丙烯腈的加成反应

手性催化剂催化下的不对称合成反应是近年来不对称合成研究中受到重视的领域，如在手性催化剂如，在手性冠醚，手性镧配合物、手性硒、手性铑及手性脯氨酸铷盐等催化下，醛、酮与二烃基锌形成手性醇和不对称羟醛缩合反应等，催化下通过Michael加成反应合成手性化合物的方法近年来也有报道，     

Development of a chiral host system tunable via changes in a 21-column packing structure

A tunable chiral host system was developed by the self-assembly of a chiral 2₁-column structure formed from (1R,2R)-1,2-diphenylethylenediamine and dicarboxylic acid. This host system can include guest molecules by changing the packing of a chiral 2₁-column enantioselectively.     

Darstellung von 2′,3′-Dideoxy-2′-hydroxymethyl-nucleosiden

Zusammenfassung Die Synthese von geschützten 2,3-Dideoxy-2-hydroxymethyl-nucleosiden wird beschrieben. Die durch ein Mehrstufenverfahren aus Isopropylidenglycerol erhaltenen Nucleoside können als Bausteine zur Darstellung von Oligonucleotiden verwendet werden, deren 2- und 5-Positionen über eine Etherbrücke verbunden sind.

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Synthesis of 2,3-dideoxy-2-hydroxymethyl nucleosides

Summary The synthesis of protected 2,3-dideoxy-2-hydroxymethyl nucleosides is presented. The nucleosides, obtained in a multi-step procedure starting from isopropylideneglycerol, may be used as building blocks for the synthesis of 2,5-ether linked oligonucleotides.

     

Novel imidazolium chiral ionic liquids that contain a urea functionality

Nine chiral room temperature ionic liquids (RTILs), which contain a chiral moiety and a urea functionality bonded to a imidazolium ring, have been designed and synthesized. The synthesis of these ionic liquids is concise and practical due to the commercial availability of the starting materials. These novel RTILs were readily prepared from 1-(3-aminopropyl)imidazole and amino acid ester derived isocyanates. We envision that these new chiral RTILs can serve as effective reaction media as well as chiral catalysts, which are presently being investigated in our laboratory.     

Crystalline Degradation Products of Vancomycin as a New Chiral Stationary Phase for Liquid Chromatography

Two crystalline degradation products (CDP-1-M and CDP-1-m) are formed from vancomycin by hydrolytic loss of ammonia. The CDP are structurally similar to vancomycin, with two carboxyl groups, but are biologically inactive. In this work the CDP of vancomycin have been covalently linked to silica gel and their ability to resolve racemic mixtures, their stability, and their loading has been evaluated by HPLC. Elemental analysis and scanning electron microscopy were used to monitor the surface of this new stationary phase. Enantiomeric separation was achieved for some compounds that have not been previously been separated on other chiral stationary phases.     

Highly enantioselective synthesis and potential biological activity of chiral novel nucleoside analogues containing adenine and naturally phenol derivatives

This paper described an efficient synthetic strategy for chiral acyclic nucleoside analogues containing both the phenoxy components of some bioactive natural compounds and a heterocyclic base. The phenoxy components with adenine moiety were incorporated into the chiral acyclic nucleoside analogues through two key synthetic tactics. Chiron 5-(R)-menthyloxy-2(5H)-furanone 5 was obtained in good yield from the cheap starting material furfural via a valuable synthetic route. The asymmetric Michael addition of 5 with adenine and the subsequent reduction reaction afforded the key chiral intermediate, 2-(R)-(9′-adeninyl)-1,4-butanediol 8. The absolute configuration of 8 was established by X-ray crystallography. The intermolecular dehydration reaction between 2-(9′-adeninyl)-1,4-butanediol 8 and phenoxy components 9 on treatment with diethyl azodicarboxylate and triphenylphosphine was carried out to give the chiral acyclic nucleoside analogues 1a-1e. The regioselectivity of the reaction was established by NMR methods, especially through ¹³C NMR shifts and NOE effect observed in the target molecule 1c, as well as by HMBC/HMQC experiments. The target compounds were tested for inhibition of cytopathogenicity against different cancer cells and exhibited potential anticancer activity.     

Stereoselective synthesis of cobalt(III) anionic complexes with chiral pyruvylaminoacid oximes and metal–ligand interactions in aqueous solution

A series of cobalt(III) anionic complexes with hydroxyimino analogs of dipeptides – oximes of pyruvylglycine, pyruvyl-l-alanine, pyruvyl-l-methionine and pyruvyl-l-phenylalanine (H₂pamaco, amac = amino acid) of composition Cat₃[Co(H₋₁pamaco)₂] · nH₂O (Cat – a monovalent metal cation) has been synthesized and investigated by UV–Vis, CD and ¹H NMR spectroscopy. It was established that for the two latter ligands, non-racemic mixtures of two diastereomeric complexes were formed as a result of synthesis. In comparison with the complex containing pyruvyl-l-alanine, in which the relative content of R (C₂) and S (C₂) isomers is approximately equal, the presence of bulky substituents in the molecules of Met- and Phe-containing ligands results in a significant discrimination in formation of the S (C₂) isomer. This conclusion was drawn upon analysis of the CD and NMR spectral data as well as from molecular modeling. The relative content of the diastereomers was evaluated on the basis of NMR data. The protonation constants of the ligands have been determined in aqueous solution by glass electrode potentiometry, whereas their interactions with Co(II) were studied both under argon and oxygen atmosphere.