A chiral metal-organic framework{(HQA)(ZnCl_(2))(2.5H_(2)O)}n for the enantioseparation of chiral amino acids and drugs

Chiral metal-organic frameworks(CMOFs)with enantiomeric subunits have been employed in chiral chemistry.In this study,a CMOF formed from 6-methoxyl-(8S,9R)-cinchonan-9-ol-3-carboxylic acid(HQA)and ZnCl_(2),{(HQA)(ZnCl_(2))(2.5H_(2)O)}n,was constructed as a chiral stationary phase(CSP)via an in situ fabrication approach and used for chiral amino acid and drug analyses for the first time.The{(HQA)(ZnCl_(2))(2.5H_(2)O)}n nanocrystal and the corresponding chiral stationary phase were systematically characterised using a series of analytical techniques including scanning electron microscopy,X-ray diffraction,Fourier transform infrared spectroscopy,circular dichroism,X-ray photoelectron spectroscopy,thermogravimetric analysis,and Brunauer-Emmett-Teller surface area measurements.In opentubular capillary electrochromatography(CEC),the novel chiral column exhibited strong and broad enantioselectivity toward a variety of chiral analytes,including 19 racemic dansyl amino acids and several model chiral drugs(both acidic and basic).The chiral CEC conditions were optimised,and the enantioseparation mechanisms are discussed.This study not only introduces a new high-efficiency member of the MOF-type CSP family but also demonstrates the potential of improving the enantioselectivities of traditional chiral recognition reagents by fully using the inherent characteristics of porous organic frameworks.

Enantiomeric Excess Determination of Amino Acids with Chiral Cyclopalladated Ferrocenylimine

An efficient NMR determination of the enantiomeric excess of the amino acids can be achieved using chloro-bridged dimer R- (+)-{Pd [(eta(5)-C5H5)Fe (eta(5)-C5H3CMe=NAr)] (mu-Cl)}2 (Ar=p-CH3C6H4) (R-1).

Carboxymethyl-β-cyclodextrin for Chiral Separation of Amino Acids Derivatized with Fluorescene-5-isothiocyanate by Capillary Electrophoresis and Laser-induced Fluorescence Detection

A method using carboxymethyl-b-cyclodextrin (CM-b-CD) as selector for chiral separation of amino acids by capillary electrophoresis and laser-induced fluorescence detection was studied. Resolution was better than that obtained by b-CD or HP-b-CD.

Syntheses and Structural Characterization of Dimethyltin Complexs of N-(3-Methoxysalicylidene)-α-amino Acid

Three new dimethyltin complexes of N-（3-methoxysalicylidene）-α-amino acid,（CH3）2Sn（3-CH3O-2-OC6H3CH=NCHRCOO）（R = H,1;CH3,2;（CH3）2CH,3）,have been synthe-sized by treating dimethyltin dichloride with the potassium salt of the ligand and characterized by elemental analysis,IR and 1H NMR spectra.The crystal structure of [（CH3）2Sn（3-CH3O-2-OC6H3CH=NCH2COO）（CH3OH）]2 H2O（1a）,formed from methanol solution of 1,has been deter-mined.The crystal belongs to the monoclinic system,space group C/2c with a = 20.636（3）,b = 7.8854（9）,c = 20.668（2） ,β= 113.265（2）°,V = 3089.7（6） 3,Z = 4,Dc = 1.707 g/cm3,= 1.675 mm-1,F（000） = 1592,R = 0.0301 and wR = 0.0841.In complex 1a,the tin atom is six-coordinate and possesses a distorted [SnC2NO3] octahedral geometry with the two methyl groups occupying the trans positions.The weak Sn O interactions and intermolecular hydrogen bonds connected the molecules into an infinite chain.

A 3D Homochiral Mn(Ⅱ) Coordination Polymer Based on the Ligand 2,2'-(Ethane-1,2-diylbis(oxy)) Dicinnamic Acid

A 3D homochiral coordination polymer [Mn（edca）]n（1） was synthesized from a flexible coupled cinnamic acid ligand, 2,2？-（ethane-1,2-diylbis（oxy）） dicinnamic acid（H_2 edca） and MnCl_2×4 H_2 O under solvothermal conditions. The complex crystallizes in orthorhombic, space group P2_12_12_1 with a = 5.5785（8）, b = 13.0393（18）, c = 23.133（3） A, V = 1682.7（4） A^3, M_r = 407.27, D_c = 1.608 Mg/cm^3, F（000） = 836, Z = 4, the final R = 0.0240 and wR = 0.0590 for 2983 observed reflections（I 〉 2σ（I））. In 1, the edca2＋ anions alternately bridge the Mn（Ⅱ） cations to form one-dimensional（1 D） infinite helical chains of [Mn（edca）]n, which are further connected by the ligands generating a three-dimensional（3D） homochiral network. The photoluminescence of 1 was also investigated in solid state at ambient temperature.

Synthesis, Crystal Structure and Properties of a Chiral 3D Supramolecular Coordination Polymer [Co(HL)·(DMF)]_n from 5-(Imidazol-1-ylmethyl)isophthalic Acid

A chiral supramolecular coordination polymer, [Co（HL）·（DMF）]n（1）, with helical chains from a flexible ligand 5-（imidazol-1-ylmethyl）isophthalic acid（H2L） has been obtained under hydrothermal conditions and characterized by elemental analysis, powder X-ray diffraction（PXRD）, IR, Uv/vis spectra, thermal gravimetric analyses（TGA） and also by single-crystal X-ray diffraction. It crystallizes in hexagonal, space group P6522 with a = 8.8109（3）, b = 8.8109（3）, c = 71.771（3） , γ = 120°, V = 4825.3（3） -3, Z = 6, Mr = 695.55, Dc = 1.436 g/cm-3, Rint = 0.0684, F（000） = 2166, the final R = 0.0923 and w R = 0.2697 for 3056 observed reflections（I 2σ（I））. The title coordination polymer 1 shows a chiral layered structure based on right-handed helix chains. Such layers are associated together through hydrogen-bonding interactions to form a 3D supramolecular framework.

Theoretical Investigation on the Second-order Nonlinear Optical Properties of Chiral Amino Acid Zinc(Ⅱ) Porphyrins

Static second-order nonlinear optical effects of amino acid zinc(II) porphyrins 1, 2, 3 and 4 were calculated by the TDHF/PM3 method based on the molecular structures optimized at the semiempirical PM3 quantum chemistry level, showing due to the cancellation of symmetric center, these amino acid zinc(II) porphyrins exhibit second order nonlinear optical response. The analysis of β components indicated that these amino acid zinc(II) porphyrins are of multipola- rizabilities, and they may be ascribed as the “mixture” of octupolar and dipoar molecules with ||βJ=3||/||βJ=1|| ≈ 5. It is found that there are no significant differences between the static β values of non-chiral and chiral amino acid zinc(II) porphyrins. However, the βxyz component, which is quite important to quadratic macroscopic χ (2) susceptibility of chiral material, is increased significantly with the increase of side chain group of amino acids.

A practical synthesis of trifluorophenyl R-amino acid:The key precursor for the new anti-diabetic drug sitagliptin

Sitagliptin is the first new anti-diabetic drug in DPP-Ⅳ inhibitor class. The general synthesis of sitagliptin is by coupling of the β-amino acid fragment with the heterocycle fragment. Though the specific β-amino acid can be easily made from the corresponding R-amino acid by Arndt-Eistert hornologation, the optically pure precursor R-amino acid is difficult to prepare. We herein reported a practical protocol to make the trifluorophenyl substituted R-amino acid 4 in 〉99.9% ee and 40.3% yield by the enzymatic resolution employing enantioselective hydrolysis and a general separation procedure. This protocol requires only cheap starting materials and friendly reaction condition. The procedure not only allows people to prepare the drug substance, but also provides an alternative method for prepareing the rare α-amino acid and the subsequent β-amino acid.

Chirality pairing recognition,a unique reaction forming spiral alkaloids from amino acids stereoselectively in one-pot

A novel chirality pairing recognition was found between D-and L-amino acid derivatives.Novel spiral alkaloids formed in the recognition reaction.Possible mechanism was proposed for the stereoselective and chemoselective reactions.

A Novel Chiral Cd-organic Network Based on Flexible Coupled Cinnamic Acid

A new metal-organic network, [Cd（CH_3OH）_2（epa）]_n（1）, was synthesized from an achiral coupled cinnamic acid, 3,3？-（（ethane-1,2-diylbis（oxy））bis（2,1-phenylene））diacrylic acid（H_2epa）, and Cd（NO3）2·4H2O under solvothermal conditions. The complex crystallizes in orthorhombic, space group P2_12_12 with a = 9.8286（8）, b = 21.0004（16）, c = 5.5169（4） A, V = 1138.71（15） A3, M_r = 528.81, D_c = 1.542 Mg/cm3, F（000） = 536, Z = 2, the final R = 0.0345 and wR = 0.1101 for 2006 observed reflections（I 〉 2σ（I））. In 1 the epa^（2＋） anions alternately bridge the Cd（II） cations to form a one-dimensional（1D） infinite homochiral helical chain of [Cd（epa）]n. The chiral homohelical chains via hydrogen bonds formed a two-dimensional（2D） network. The photoluminescence of 1 was also investigated in solid state at ambient temperature.

Enantioselective extraction of mandelic acid enantiomers based on chiral ligand exchange

Based on the chiral ligand exchange, the distribution behavior of mandelic acid enantiomers, and the partition of Cu2+ at different pH values were studied in a water/alcohol two-phase system containing Cu2+ and N-n-（dodecyl-L-proline（A）.） The influences of the solvent sort, the pH value, the concentrations of Cu2+ and chiral ligand on the partition coefficient（K） and separation factor（α） were discussed. The experimental results show that the A formed has more stable ternary complex with D-mandelic acid enantiomer than with L-mandelic acid enantiomer. There is an important influence of the pH value on K and α. When the pH values are less than 3.5, the formation of binary complexes is thermodynamically unfavourable. K and α become maximum when pH values are above 3.5 and the molar ratio of the chiral ligand to Cu2+ is 2∶1.

New Chiral Calixarene Derivatives: Syntheses and Their Chiral Recognition Toward Amino Acids by UV-Vis Spectroscopy

Three novel types of chiral calixarene derivatives 5, 8, and 10 were designed and synthesized by introducing chiral units to parent calixarenes. Their chiralities were confirmed by rotational analysis. Chiral recognition properties of these host compounds towards L- and D-threonine were studied by UV-Vis spectroscopy. The results indicated that calixarene derivatives 5 and 8 exhibited good chiral recognition capabilities toward L- or D-threonine. Although calixarene derivative 10 had no evident chiral recognition ability, the supramolecules of calixarene derivative 10 with L- or D-threonine showed a hypochromic effect or hyperchromic effect respectively. Therefore, calixarene derivative 10 might serve as a good chiral UV-indicator.

Using the Chiral Organophosphorus Derivatizing Agents for Determination of the Enantiomeric Composition of Chiral Carboxylic Acids by ^(31)PNMR Spectroscopy

The use of chiral organophosphoras derivatizing agents prepared in situ from chiral tartrate or chiral diamine for the 31PNMR determination of the enantiomeric composition of chiral carboxylic acids is described. The method is accurate, reliable and convenient.

DiastereoselectiveandEnantioselectiveSynthesisof(1S,2S)-2-Ethyl-1-aminocyclopropaneCarboxylicAcid

Pd(0) Complex prepared from Pd(dba)(2) and chiral quinolinyl-oxazoline ligand can catalyze alkylation and cyclization reaction of 1, 4-dichlorobut-2-ene 1 with anion of N-(diphenylmethylene)amino acetonitrile 2 to provide (E)-2-ethenyl-1-N-(diphenylmethylene) amino cyclopropane carbonitrile 3 with 100% de and 20% cc. Reduction of (E)-3 by diimide followed by acidic hydrolysis afforded (1S, 2S)-2-ethyl-1-aminocyclopropanecarboxylic acid 9, a natural product coronamic acid.

Synthesis of Chiral Amino Cyclic Phosphoric Acids

Chiral amino cyclic phosphoric acids, 5-amino-2-hydroxy-4-(4-nitrophenyl)-1,3,2-dioxaphosphorinane 2-oxide and 2-hydroxy-4-(4-methylsulfonylphenyl)-5-phthalimido-1,3,2-dioxaphos phorinane 2-oxide are synthesized in good over yields (64.2%and 72.8%respectively) from 2-amino-1-aryl-1,3-propanediols. The different reaction conditions are necessary in hydrolysis reactions of amino cyclic phosphonyl chlorides.

Chiral Discrimination in N-(O, O-dialkyl)phosphoamino Acid Monolayers at the Air-water Interface

In this paper, chiral discrimination in N-(O,O-dialkyl)phosphoamino acid monolayers at the air/water interface was studied and it was revealed that the D:L=1:1 racemic monolayer of N-(O, O-dihexadecyl)phosphoalanine is packed more densely in solid phase while shows a higher LE to LC transition pressure than the enantiomeric ones.

Synthesis of a New Chiral Cyclicβ-Amino Alcohol

A new chiral cyclic β-amino alcohol (R)- 1 -(l '-amino-2'-naphthylethyl)-cyclopentanol2, which had notbeen reported previously, was prepared from (R) - 3 - (2 - naphthy1 )- alanine 3.

Novel Method for Selective Debenzylation Under Maintenance of Fluoro Atom Substituted on β-Amino Acids

tert-Butyl （R）-3-amino-3-（3-fluorophenyl）propanoate（5） was prepared with conventional debenzylation method. However, the tert-butyl （R）-3-[（S）-1-phenylethyl-amino]-3-（3-fluorophenyl） propanoate（6） and tert-butyl （R）-3-amino-3-phenylpropanoate（7） were generated as the byproducts under the general catalytic hydrogenation Pd（OH）2/C-H2 conditions. So a series of experiments was performed to optimize the reaction conditions so that product 5 could be obtained with high purity and yield. Finally an effective catalytic system, Pd/C-HCOOH-CH3OH, was discovered.

Synthesis,Characterization and Structure of Chiral Amino Acids and Their Corresponding Amino Alcohols with Camphoric Backbone

Chiral amino acids and their corresponding amino alcohols bearing camphoric backbone were prepared from D-（＋）-camphoric imide and characterized by infrared, elemental analysis, ESI-MS, and NMR measurements. Among them, one intermediate （1S,3R）-3-amino-2,2,3- trimethyl cyclopentane-1-carboxylic acid hydrochloride 3 was structurally elucidated by X-ray diffraction techniques. Versatile intermolecular hydrogen bonding interactions observed in its packing structure result in a two-dimensional framework.

Study on Bicoordination Chiral Inducement Catalysis of (R)-4-Thiazolidinecarboxylic Acid

The bicoordination chiral inducement catalysis of (R)-4-thiazolidinecarboxylic acid inthe enantioselective borane reduction of prochiral ketones has been studied. The fact that theabsolute configuration of the main product can be changed by simply using different operationmethods was firstly verified. And the reason of bicoordination chiral inducement was discussed.