Molecular origin for helical winding of fibrils formed by perfluorinated gelators

A chiral low-molecular weight gelator, N,N'-diperfluoroheptanoyl-1,2(R,R)- or -1,2(S,S)-diaminocyclohexane, was prepared to form a gel of acetonitrile. The conformation of the gelator in fibrils was determined by vibrational circular dichroism spectra, providing a molecular model for self-assembly in a helical fibril.     

Organic reactions in supramolecular gel media: reaction driven release of reagents in a macrocyclisation reaction

A bifunctional reactive organogelator containing p-nitrophenyl carbamate moieties has been reacted with (1R,2R)-(+)-1,2-diphenyl-1,2-ethanediamine to produce a l-valine derived macrocyclic bisurea. The macrocyclisation can be carried out very efficiently in the presence of the supramolecular gel formed by the biscarbamate, although the results indicate that the reaction takes place on the soluble species present in the system. The reversible nature of a supramolecular gel together with the high active surface of its fibrillar network permits the behaviour of the studied gel as an on-demand supplier of reagents to the solution phase.     

Synthesis,crystal structure,and magnetic characteristics of chiral cyanide-bridged Fe–Cu complex

Based on the building blocks, trans-dicyanide Fe(III) precursor and chiral amine Cu(II) compound, the chiral cyanide-bridged heterometallic Fe(III)–Cu(II) complex with the formula {[Cu(R/R-Chxn)₂Fe(bpmb)·(CN)₂][Fe(bpmb)(CN)₂]}·CH₃OH·H₂O (1) [bpmb^2– = 1,2-bis(pyridine-2-carboxamido)-4-methylbenzenate, R,R-Chxn = R,R-1,2-diaminocyclohexane] has been synthesized and characterized by elemental analysis, IR spectra and X-ray analysis. The latter revealed that the complex contained the cyanide-bridged cationic binuclear entity and free anionic cyanide building block. The complex demonstrated weak ferromagnetic coupling between neighboring Fe(III) and Cu(II) ions via the bridging cyanide group.     

Synthesis of Some New Chiral Sulfonamide Ligands

Synthesis of new chiral sulfonamide ligands derived from isatoic anhydride by reaction with trans-(R,R)-1,2-diaminocyclohexane and chiral aminoacid esters.     

Chromatographic evaluation of poly (trans-1,2-cyclohexanediyl-bis acrylamide) as a chiral stationary phase for HPLC

Chiral stationary phases (CSPs) based on polymeric (R,R)- or (S,S)-1,2-diaminocyclohexane (DACH) derivatives are synthesized. When bonded to 5 microm porous spherical silica gel, the poly (trans-1,2-cyclohexanediyl-bis acrylamide) based poly-cyclic amine polymer (P-CAP) stationary phases is proved to be effective chiral stationary phases that could be used in the normal-phase mode, polar organic mode and with halogenated solvents mobile phases, if desired. Since these are entirely synthetic CSPs, the elution order of all enantiomers can be reversed between the (R,R) P-CAP and (S,S) P-CAP columns. Because of the high loading of chiral selectors, the columns exhibit very high sample capacities. Thus, P-CAP columns are useful for preparative and semi-preparative enantiomeric separations. The application of these CSPs and optimization of their separations are discussed.     

Direct resolution of racemic compounds on chiral microbore columns by sub- and supercritical fluid chromatography

Fast resolutions of racemic compounds (sulfoxides, amino alcohols, and α-methylarylacetic acids derivatives) were achieved on a chiral microbore column using carbon dioxide and a polar methanol/dioxane modifier. The stationary phase used in this study contains the 3,5-dinitrobenzoyl derivative of R,R(?)-1,2-diaminocyclohexane (DACH-DNB) as the chiral moiety, anchored to a silica gel surface by covalent bonds. Both thermodynamic and kinetic separation performances were improved by using a super- or subcritical carbon dioxide mobile phase (SFC, SubFC).     

General approach to low-molecular-weight metallogelators via the coordination-induced gelation of an L-glutamate-based lipid

A twin-tailed glutamate-based lipid with a pyridine headgroup was prepared in good yield using standard amide coupling and protection/deprotection chemistry. The resulting Lewis basic lipid gels a wide array of hydrocarbon solvents at a critical gelation concentration (C(g)) of 0.3 wt %. The gelation of more polar solvents, such as ethanol, THF, dichloromethane, and chloroform, occurs with a C(g) of between 2 and 5 wt %, demonstrating the importance of hydrogen bonding interactions in gel formation. The importance of hydrogen bonding in this system was also demonstrated by IR observation of the amide bands, which show a substantial shift upon gelation. Solutions of this new organogelator with concentrations below C(g) rapidly form gels upon the introduction of a wide variety of metal salts or complexes, providing a convenient general method for the preparation of metallogelators. Spectroscopic evidence suggests that the enhanced gelation seen in the metal-containing systems can be explained by a cross-linking of gel fibril aggregates similar to those formed by the unmetalated gelator.     

Dendrimer-Like Chiral Stationary Phases Derived from (1R, 2R)-(+)-1,2-Diphenylethylenediamine and 1,3,5-Benzenetricarbonyl Trichloride

Three dendrimers were synthesized directly on aminated silica gel using (1R, 2R)-(+)-1,2-diphenylethylenediamine and 1,3,5-benzenetricarbonyl trichloride as building blocks. The chiral stationary phases were obtained by modification of these dendrimers with phenyl isocyanate. All derivatives prepared on silica gel were characterized by FTIR spectrum, solid-state ¹H NMR and elemental analysis. The enantioseparation ability of the chiral stationary phases was preliminarily evaluated by high-performance liquid chromatography. The chiral stationary phase of one-generation dendrimer exhibited best enantioseparation ability.     

Promotion effects of optical antipodes on the formation of helical fibrils: chiral perfluorinated gelators

A chiral gelator, RR- or SS-N,N'-diperfluorooctanoyl-1,2-diaminocyclohexane, gelated racemic 2-butanol. The gel was most stable at the racemic mixture, its stability lowered with the increase in the optical purity of the gelator. Notably, characteristic helically coiled fibrils were formed in the narrow region of enantiomer excess (ee = 0.2-0.4). Promotion effects of the antipodal enantiomers are proposed.     

A chiral molecular bowl containing three ferrocenes: synthesis and its efficiency in an optical resolution of 1,1'-bi-2-naphthol

Condensation reaction of 1,1'-ferrocenedicarboxaldehyde with (1R,2R)-1,2-diaminocyclohexane affords a novel bowl-shaped macrocycle with a chiral concave cavity which exhibits a remarkable ability as a host material for the enantioselective enclathration of 1,1'-bi-2-naphthol.     

Chiral iminospherand of a tetrahedral symmetry spontaneously assembled in a [6 + 4] cyclocondensation

Thermodynamically driven cyclocondensation of (R,R)-1,2-diaminocyclohexane and 1,3,5-triformylbenzene yields solely a [4 + 6] spherand type product. This is a unique example of spontaneous formation of an organic compound of permanent chiral tetrahedral (T) symmetry.     

Mononucleotide recognition by cyclic trinuclear palladium(II) complexes containing 4,7-phenanthroline N,N bridges

Reaction of [(dach)Pd(NO3)2] entities (dach = (R,R)-1,2-diaminocyclohexane, (S,S)-1,2-diaminocyclohexane) and 4,7-phenanthroline (phen) providing, respectively, 90 and 120 degrees bond angles, leads to the formation of two novel positively charged homochiral cyclic trinuclear metallacalix[3]arene species [((R,R)-1,2-diaminocyclohexane)Pd(phen)]3(NO3)6 (2a) and [((S,S)-1,2-diaminocyclohexane)Pd(phen)]3(NO3)6 (2b). These species have been characterised by 1)H NMR and X-ray diffraction methods (2b), showing that they possess accessible cavities suited for supramolecular recognition processes. We prove, indeed, from 1H NMR studies the inclusion of mononucleotides inside the cavity of the trinuclear species [(ethylenediamino)Pd(phen)]3(6+) (1), [((R,R)-1,2-diaminocyclohexane)Pd(phen)]3(6+) (2a) and [((S,S)-1,2-diaminocyclohexane)Pd(phen)]3(6+) (2b) in aqueous solution. Association constants (K(ass)) range from 85 +/- 6 M(-1) for the interaction between [(ethylenediamine)Pd(phen)]3(6+) and adenosine monophosphate to 37 +/- 4 M(-1) for the interaction between [(1,2-diaminocyclohexane)Pd(phen)]3(6+) and thymidine monophosphate. We invoke the synergy of electrostatic, anion-pi and pi-pi interactions to explain the recognition of mononucleotides inside the cavity of the metallacalix[3]arenes.     

Synthesis and Characterization of New Chiral Schiff Base Complexes with Diiminobinaphthyl or Diiminocyclohexyl Moieties as Potential Enantioselective Epoxidation Catalysts

New chiral Schiff base complexes have been obtained by condensation of 2,2'-diamino-1,1'-binaphthalene or 1,2-diaminocyclohexane and various salicylaldehydes and by subsequent metalation with manganese, iron, cobalt, nickel, copper, or zinc. The complete (1)H and (13)C NMR characterization of the ligands is reported, as are the X-ray crystal structures of (1R,2R)-(-)-N,N'-bis[3-(N,N-dimethylamino)salicylidene]-trans-1,2-cyclohexanediimine and [(1R,2R)-(-)-N,N'-bis(salicylidene)-trans-1,2-cyclohexanediiminato]copper(II). The new chiral manganese complexes have been evaluated in the oxygenation of prochiral olefins and sulfides using sodium hypochlorite, hydrogen peroxide, or N-methylmorpholine N-oxide/m-chloroperbenzoic acid as oxidant.     

Kinetic resolution of esters via metal catalyzed methanolysis reactions

Some chiral lanthanide complexes of the Schiff base adducts of: a) bis(2-pyridylcarboxaldehyde) and (1R),(2R)-trans-1,2-diaminocyclohexane (Pyr-R,R'-chxn: 3); b) 6-methyl-2-pyridylcarboxaldehyde and (1R),(2R)-trans 1,2-diaminocyclohexane (MePyr-chxn, 4); and c) 2,6-pyridyldicarboxaldehyde and (1R),(2R)-trans-1,2-diaminocyclohexane ((Pyr-R,R'-chxn)(2), 5) have been screened for their utility to promote kinetic resolution via metal catalyzed alcoholyses of the p-nitrophenyl esters of chiral D- and L-Boc-protected glutamine and phenylalanine. Solvents were varied to optimize the kinetic selectivity values, defined as k(2)(L)/k(2)(D) or k(2)(D)/k(2)(L), for the methanolysis and in some cases, ethanolysis of these substrates. At ambient temperature the greatest selectivity was found for the ethanolysis of Boc-Gln-OPNP, catalyzed by 3:Yb(3+):((-)OEt) (k(2)(L)/k(2)(D) = 7.2). The greatest selectivity for Boc-Phe-OPNP is k(2)(D)/k(2)(L) = 3.9 for its methanolysis promoted by 5:La(3+):((-)OMe). A kinetic method is introduced for the determination of both d and l rate constants for catalyzed alcoholysis from a single kinetic experiment. The activation parameters DeltaH(double dagger) and DeltaS(double dagger) were determined for the metal catalyzed methanolysis and ethanolysis of the Boc-Gln-OPNP substrates, and selectivity factors were found to increase at lower temperatures. A low temperature time course for the ethanolysis of racemic Boc-Gln-OPNP catalyzed by 3:Yb(3+):((-)OEt) at -15 degrees C indicated that after 3 hours 60% residual d-enantiomer was observed having an enantiomeric excess of >95% ee. The activation parameters for the ethanolysis of the same substrate catalyzed by (Pyr-R,R'-chxn)(2):La(3+):((-)OEt) predict a k(2)(D)/k(2)(L) = 40.4 at -40 degrees C with a large ee of >99% with approximately 80% of l isomer remaining at that temperature which has been experimentally confirmed.     

Synthesis and characterisation of macrocyclic diamino chiral crown ethers

A benign and efficient synthesis of chiral macrocyclic 'aza-crown' ethers of varying ring size is reported. The synthesis involves a Schiff base condensation of ether linked dialdehydes of varying chain length and (1R,2R)-(-)-1,2-diaminocyclohexane under mild conditions to yield the macrocycles, which are subsequently reduced to yield the diamino analogues.     

环己二胺类手性席夫碱配体的合成与表征

以(R,R)-1,2-环己二胺为手性源,同水杨醛及带有叔丁基,溴或硝基的取代水杨醛反应合成了5个手性席夫碱配体。其结构经^1H NMR,^13C NMR,IR和MS表征,并测定了其熔点和比旋光度。     

Direct Chromatographic Resolution of P-Chiral Organophosphorus Compounds at Analytical and Preparative Levels

Abstract

High-performance liquid chromatography utilizing chiral stationary phases (CSPs) is well established as a very simple and efficient method for obtaining discrete amounts of optically active compounds with high e.e., as well as for determining their enantiomeric composition We wish to demonstrate in the present work that a totally synthetic brush-type π-acidic CSP based on a bis(N,N′-3,5-dinitrobenzoyl) derivative of (R,R)- or (S,S)-trans-1,2-diaminocyclohexane as selector can be used successfully to resolve variety of chiral organophosphorus compounds containing stereogenic centers at phosphorus     

Edge-directed dynamic covalent synthesis of a chiral nanocube

The dynamic multicomponent syntheses of nanometer-sized chiral molecular cubes 1a and 1b from 8 tritopic 90 degree corner units and 12 linear spacers using an edge-directed approach is described. Thus, the TFA-catalyzed reaction of 8 equiv C3-trihexadecyloxy-triformylcyclotribenzylene 2 as corner unit with 12 equiv of 1,4-phenylenediamine 3a or benzidine 3b as spacers yields nanocubes 1a and 1b, respectively in close to quantitative yield. The same reactions carried out with enantiomerically pure (P)-2 (>99% ee) gave the homochiral cubes (all-P)-1a and (all-P)-1b. Force field calculations predict an edge length of 17 A and 21 A for 1a and 1b, which is consistent with their dimensions estimated from DOSY experiments. Furthermore, the asymmetric synthesis of (P)-2 through a dynamic thermodynamic resolution is described. This approach is based on the TFA-catalyzed reaction of racemic 2 with (R,R)-1,2-diaminocyclohexane (R)-5, which leads to a chiral cryptophane (>90% yield) that is built-up from two (P)-2 linked together with three diamines (R)-5. Hydrolysis of this cryptophane provides (P)-2 with >99% ee.     

Crystal or low molecular mass organogel based on sugar-derived chiral pyrano[2,3-b]naphtho[1,2-e]pyrans

[structure: see text] 2-C-Acetoxymethyl glycal derivatives reacted with beta-naphthol in the presence of InCl(3) (30 mol %) to give chiral pyrano[2,3-b]naphtho[1,2-e]pyrans in good to excellent yields via stereoselective Ferrier rearrangement-tandem cyclization. The major glucose-derived product exhibited crystal packing with C-H...O and C-H...pi (arene) interactions and the major galactose-derived product, a low molecular mass organogelator (LMOG), formed a rare type of micro tubular gel assembly in n-hexane.     

Controlling the macrocycle size by the stoichiometry of the applied template ion

Reaction of 4-tert-butyl-2,6-diformylphenol with (1R,2R)- or (1S,2S)-1,2-diaminocyclohexane in the presence of 1 equivalent of Zn(2+) ions leads to selective formation of a chiral 2+2 macrocycle. Application of 0.5 equivalent of Zn(2+) ions under the same conditions leads to selective formation of a chiral 3+3 macrocycle, which forms a cavitand-shaped trinuclear double-decker complex with Zn(II).