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A class of carbonyl extractors, (R)-3, (R)-4, and (R)-5, with nonaxial chirality containing asymmetric carbons has been synthesized and studied for their efficiencies in enantioselective liquid-liquid extraction for underivatized amino acids. The bulky t-butyl ketone extractors, (R)-4 and (R)-5, showed the stereoselectivities ranging 5.4-9.4 of l/d ratio much better than those of the aldehyde extractor, (R)-3, ranging 2.4-5.2. The imine formation rates and yields of the t-butyl ketones were not significantly affected by their bulkiness and even in the absence of resonance-assisted hydrogen bond. This work confirms that a bulky t-butyl ketone can be a good choice in the development of an extractor not only with axial chirality but also with nonaxial chirality for the enantioselective extraction of unprotected amino acids.

A stereodynamic chiroptical sensor based on three-component assembly of 3-(di-2-picolylaminoacetamido)-2-formyl-naphthalene (1), ZnII and amino acids was developed. The imine formed between 1 and an amino acid has six coordination sites to bind tightly ZnII ion. The crystal structure of the ZnII complex, 1-Zn-D-Phe, revealed that the naphthyl ring is tilted to one pyridine ring to generate axial chirality. The dihedral conformations observed in 1-Zn-D-Phe were herein arbitrarily designated as α1 and α2. DFT calculation suggests that the D-Phe binding prefer the α1-conformer: the energy of D-Phe-α1 is more stable than L-Phe-α1 by 5.5 kcal/mol. This preference to one diastereomer generates amplification of CD signal with Cotton effect, which can be applied to the determination of ee values of the amino acid.

Scalable and economical methods for the production of optically pure amino acids, both natural and unnatural, are essential for their use as synthetic building blocks. Currently, enzymatic dynamic kinetic resolution (DKR) underpins some of the most effective processes. Here we report the development of enantioselective extraction coupled with racemization (EECR) for the chirality conversion of underivatized amino acids. In this process, the catalytic racemization of amino acids in a basic aqueous solution is coupled with the selective extraction of one enantiomer into an organic layer. Back-extraction from the organic layer to an acidic aqueous solution then completes the deracemization of the amino acid. The automation of the EECR process in a recycling flow reactor is also demonstrated. Continuous EECR is made possible by the sterically hindered chiral ketone extractant 5, which prevents the coextraction of the copper racemization catalyst because of its nonplanar geometry. Furthermore, the extractant 5 unexpectedly forms imines with amino acids faster and with greater enantioselectivity than less bulky derivatives, even though 5 cannot participate in intramolecular resonance-assisted hydrogen bonding. These features may allow EECR to challenge the preponderance of enzymatic DKR in the production of enantiomerically enriched amino acids., Dynamic kinetic resolution is a common approach for the preparation of optically pure amino acids using enzymes. Here the authors report an alternative method based on enantioselective extraction coupled with racemization, in which a bulky extractant affords hydrophobic extractable imines with amino acids rapidly, reversibly and enantioselectively.

A novel multifunctional aminophenylboronic acid connected to a diphenylketone gives both circular dichroism and fluorescence signals by in situ generation of a BODIPY-like chromophore in the presence of aminoalcohols. DFT calculations were used to understand the role of each functional group in the mechanism. This new sensor can distinguish different aminoalcohols and quantitatively indicate the concentration of the substrate, allowing for the convenient determination of the ee of racemic mixtures with a single probe.

Axially chiral binaphthoic acid (BNA) was studied as a resolving agent for a stereoselective crystallization of 1-(4-chlorophenyl)ethylamine (CPEA). The diastereomeric pair of (R)-BNA/(S)-CPEA crystallizes in methylene chloride, on the other hand, the pair of (S)-BNA/(S)-CPEA crystallizes in acetone. The switch of the solubility of the diastereomeric pair is due to the imine formation with acetone. The very low solubility of the BNA/imine pair appears to be responsible for the fast and complete imine formation. The crystal structure of the BNA part in both crystals of the diastereomers maintains a same feature. Asymmetric chiral channels and pockets composed by intermolecular packing of BNA molecules appear in the crystal structures, and the robustness of them seem to contribute to the recognition of the chirality of CPEA with high selectivity.

A binaphthol aldehyde with phenyl ether linkage, compound 2, has been synthesized starting from binaphthol-3-carboxylic acid. The axially chiral binaphthol ring was racemized during the synthesis due to high temperatures required in O-phenylation reaction. The enantiomerically pure form of 2 was obtained from the resolution of the diastereomeric imine of 2. Optically pure compound (S)-2 was applied to the enantioselective liquid–liquid extraction of amino acid between CH2Cl2 and aqueous layers. The stereoselectivities, that is, d/l ratio of the amino acid extracted, ranged from 3.57 to 11.1. One carbon was absent in compound (S)-2 compared to the compound (S)-1 with benzyl ether linkage, which differentiated the conformations of their imines formed with amino acids.

Three representative BINOL derivatives were examined for their chiral recognitions with D- and L-t-Boc-amino acid anions: an open system 1, which bears two urea groups and two pyrene groups; a closed ring system 2, which bears two urea groups with a closed ring system; and a dimeric system 3, which bears two benzylic amine groups and two pyrene groups. Dimeric system 3 displayed a ΔI(D)/ΔI(L) of 12.95 for t-Boc-alanine.

The chiral ketone (S)-3 shows high kinetic enantioselectivities toward the L form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the D form for cysteine with its -SH polar side chain when used as an extractant in enantioselective liquid-liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are L-form-selective.

2-Hydroxy-6-(1-(3-phenylurylphenyl)ethoxy)-benzaldehyde (2) has been synthesized in racemic form from 1,3-Dihydroxybenzene via formylation and reaction with 3-phenyluryl-methylbenzylbromide. The optically pure form of 2 was separated by normal silica column chromatography from the imine diastreomer which was obtained by the reaction of racemic mixture of 2 with optically pure leucinol. The absolute configuration of the separated enantiomer of 2 was decided from the energy calculation of the corresponding imine diastereomers. The activity of 2 as a chirality conversion reagent (CCR) for amino acids was determined by 1 H NMR analysis. The efficiency of 2 is not better than the previous CCRs based on binaththol. Compound 2, however, has lower molecular weight compared to other CCRs. This work demonstrates that asymmetric carbon can control the selectivity of amino acids.

A new octahedral Ru(III) complex with a tripodal tetraamine ligand, tpea = tris[2-(1-pyrazoyl)ethyl]amine, has been prepared and characterized. The single crystal X-ray crystallographic study of the complex revealed that the complex has a near octahedral geometry with the tetradentate ligand and two chloride ions. Peroxidase activity was examined by observing the oxidation of 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonic acid (ABTS) with hydrogen peroxide in the presence of the complex. Amount of ABTS + generated during the reaction was monitored by UV/VIS and EPR spectroscopies. After the initiation of the peroxidase reaction, ABTS + concentration increases and then decreases after certain time, indicating that both ABTS and ABTS + are the substrates of the peroxidase activity of the Ru(III) complex.

KISTI ReSEAT program senior fellow, Korea Institute of Science and Technology Information, Seoul 130-742, KoreaReceived June 29, 2011, Accepted July 21, 2011Key Words : Conformational switching, Oxalate sensor, Diamine-platinum(II) complex, Host-guest chemistryA molecular conformational switching has been of grow-ing interest in association with molecular electronics

E-mail: rajunandha@gmail.comReceived January 29, 2011, Accepted February 15, 2011Novel binol-based uryl and guanidinium receptors having higher ring conjugation at the periphery of thehydrogen bonding donor sites have been synthesized and utilized to study the enantioselective recognition of1,2-aminoalcohols and chirality conversion of natural amino acids via imine bond formation. There is aremarkable decrease in the stereoselectivites as the conjugation increases at the periphery of hydrogen bondingdonor sites. The guanidinium-based receptors show more selectivity towards the amino alcohol than that of theuryl based ones due to its charge reinforced hydrogen bonds. The conversion efficiency of

Bis-pyrene derivative 1, bearing two pyrene and pyridine groups, was synthesized as a ratiometric fluorescent chemosensor for Ag(+) in aqueous solution. Fluorescent chemosensor 1 displayed a selective ratiometric change with Ag(+), which was attributed to the excimer-monomer emissions of pyrenes. A mechanism for the binding mode was proposed based on fluorescence changes, NMR experiments, and theoretical calculations.

Department of Chemistr/Division of Nano Sciences, Ewha Womans University, Seoul 120-750, Korea Received March 10, 2014, Accepted March 19, 2014Key Words : Amino acid, Alanine racemase chiral analogue, Chiral converter, Chiral HPLCDeracemization is the stereoselective process of convert-ing a racemate into either a pure enantiomer or a mixture inwhich one enantiomer is present in excess.

In most of these studies, molecular recognition is based on non-covalent interac-tions such as hydrogen bonding, metal coordination, and hydro-phobic interactions. In contrast, reversible covalent bond, more specifically imine formation has been rarely explored for the recognition studies. When compared to non-covalent interac-tions, imine bonds

New receptors 1-3 that bind stereoselectively amino alcohols and convert chirality of amino acidsvia imine bond formation were synthesized. The receptors have uryl (1), thiouryl (2) and guanidinium (3) groups all with additional phenylcarbonyl motifs, which are effective hydrogen bonding donors and play a key role in the stereoselective recognitions. The stereoselectivities were measured from the integration of 1 H NMR peaks. Compound 1 and 2 showed the stereoselectivities for the imine formation with amino alcohols (KR/KS) in the range of 2 ~ 4, and compound 3 in the range of 4 ~ 8. Chirality conversion efficienciesof 1-3 for amino acids, i.e. D/L ratio at equilibrium, are in the range of 1.5 ~ 5.6, showing a little higher efficiency with 3. The additional phenylcarbonyl motifs in 1-3 were revealed not to contribute to significant enhancement of the selectivities.

New rhodamine derivatives bearing binaphthyl group were synthesized as selective fluorescent and colorimetric sensors for Cu2+. Highly selective “off–on” type fluorescent changes were observed upon the addition of Cu2+. Selective fluorescent enhancement of two rhodamine derivatives was attributed to ring opening from the spirolactam (nonfluorescent) to ring-opened amide (fluorescent). A chemo-sensing based on rhodamine derivative was further applied to the microfluidic system.

with an amino acid is associated with the hydrogen bond donating sites (HBD), which plays a decisive role. In order to enhance the stereoselectvity of dipeptides, we speculated that additional HBD’s are required along with the uryl group, for effective hydrogen bonding with both the amide and carboxylate group of the peptides. Hence, we designed compound

Novel binol receptor with pyrrole-2-carboxamide moiety and its analogues have been designed, synthesized, and used to enantioselectively recognize 1,2-aminoalcohols via multiple hydrogen bonding. The pyrrole-based binol receptor showed the highest enantioselectivity among the four receptors as determined by the 1 H NMR. The DFT calculation strongly supports complementary hydrogen bonding between alcoholic –OH and pyrrolyl groups.

The uryl-based binol aldehyde, (S)-2-hydroxy-2′-(3-phenyluryl-benzyl)-1,1′-binaphthyl-3-carboxaldehyde (1), binds 1,2-amino alcohols and amino acids stereoselectively by reversible formation of imine bond. Hydrogen bond (between uryl group and alcohol –OH moiety) plays an important role in the stereoselectivity of amino alcohols. Hence, any substituents on phenyl group in 1 are expected to affect H-bond ability of uryl group. To study the effects of ring substituents on the stereoselective recognition of amino alcohols, (substituted phenyl)uryl-based chiral binol receptors have been prepared. The receptors with electron-donating X substituents have been synthesized from (S)-2-methoxymethoxy-2′-hydroxy-1,1′-binaphthyl-3-carboxaldehyde and X-phenyluryl-benzyl bromide. The receptors with electron-withdrawing Y substituents, however, required a different synthetic strategy including transformation of an aldehyde to alcohol. The incorporation of the electron withdrawing groups slightly accelerated the stereoselective recognition property of the receptor. Though the acceleration is not so remarkable, this work demonstrates the versatile derivatization of 1 in achieving higher stereoselective recognition of 1,2-amino alcohols and stereoconversion of l -amino acids to d -amino acids.

(R)-Amino alcohol with an enantiomeric excess of >95% was resolved by reactive extraction processes from 2 equiv of racemic alcohol using a chiral receptor 2 as an enantioselective extractant. One resolution cycle is composed of three extractions: a stereoselective reversible imine formation, a stereoselective irreversible imine hydrolysis, and the recovery of 2 and enantiomeric amino alcohols.

A novel auxillary chiral ketone has been designed, synthesized, and used to enantioselectively recognize 1,2-amino alcohols. This work proves that the keto group can serve as a chiral recognition center by imine formation supported by resonance assisted hydrogen bonding (RAHB).

A new fluorescent sensor based on rhodamine B for Pb2+ was synthesized. The new fluorescent sensor showed an extreme selectivity for Pb2+ over other metal ions examined in acetonitrile. Upon the addition of Pb2+, an overall emission change of 100-fold was observed, and the selectivity was calculated to be 200 times that of Zn2+. The signal transduction occurs via of reversible CHEF (chelation-enhanced fluorescence) with this inherent quenching metal ion.

Dinuclear [Cu(aepi)(N3)2]2 (1) [aepi = 1-(2-aminoethyl)piperidine] and 1D chain [Cu(aepy)(N3)2]n (2) [aepy = 1-(2-aminoethyl)pyrrolidine] have been prepared and characterized by means of X-ray analysis and magnetic measurements. For 1, the Cu(II) centers are doubly bridged by end-on (EO) azido units in a basal–apical fashion. The molecular structure of 2 features magnetic centers that are linked by μ-1,1,3 azido groups, forming a 1D chain with alternating EO and end-to-end (EE) azido bridging patterns. The magnetic data for the dinuclear complex 1 were fitted with the Bleaney–Bowers equation derived from the Hamiltonian H = −JS1 · S2, affording parameters of g = 2.093(1), J = −3.06(1) cm−1 and zJ′ = −1.32(3) cm−1. This indicates that the EO azido group mediates an antiferromagnetic interaction. Complex 2 has two possible magnetic pathways: one is through the EO azido bridge (Jeo) and the other via the EE bridge (Jee). The alternating chain model with ferromagnetic and antiferromagnetic interactions based on the exchange Hamiltonian H = −∑i[J1S2i · S2i + 1 + J2S2i · S2i − 1] was employed, leading to g = 2.076(2), J1 = −3.22(5) cm−1, J2 = 17.0(5) cm−1 and zJ′ = −1.34(6) cm−1. By taking into account structural parameters of 1 and 2, it is rationally suggested that J1 and J2 are ascribed to Jeo andJee, respectively. These assignments are also ascertained by MO calculations using a spin dimer model.

Mono(trifluoroacetato)platinum(IV) complexes of the formula [PtIV(dach)L3(TFAc)] (dach = trans-(±)-1,2-diaminocyclohexane, TFAc = trifluoroacetate, L = acetate or propionate) could be prepared from the reaction of [PtIV(dach)L3(OH)] with trifluoroacetic anhydride in the presence of a base and the crystal structure of compound 4 was determined by X-ray crystallography. In vitro antitumor activity of complex 4 (ED50 = 3.1 μM) was found to be much higher than carboplatin (ED50 = 10.2 μM).

Reaction of (triphenylmethyl)silanetriol (1) with cyclopentadienyltitanium trichloride (CpTiCl3) in the presence of triethylamine as a HCl scavenger gave both compounds of a partial open-cage type {[Ph3CSiO(OH)]3(Ph3CSiO3/2)(CpTiO3/2)4} (2) and cube type (Ph3CSiO3/2CpTiO3/2)4 (3). The 1:1 reaction of 1 and CpTiCl3 in toluene solvent at reflux temperature for 3 d afforded compounds 2 (22%) and 3 (36%). When 1 is reacted with a 1.5 fold excess of CpTiCl3 under the same conditions, compound 3 was obtained in high yield (81%) along with 2 in trace quantities. Compounds 2 and 3 were fully characterized by the analyses of 1H, 13C, 29Si NMR, IR, and FAB MS data. The solid-state structure of 3 was determined by a single crystal X-ray diffraction study. Compound 3 had shown to have catalytic activity for the oxidation of alkenes such as 1-octene, cyclooctene, and norbornene with t-butyl hydrogen peroxide. The effect of solvent was observed in this epoxidation reaction. The order of reactivity were decreased as follows: CHCl3 > hexane ≫ THF.

One-dimensional (1-D), two-dimensional (2-D), and three-dimensional (3-D) coordination polymers were prepared by self-assembly of binary metal complex systems, copper(II) nitrate and (en)Pt(II)(nic)(2) or (dmpda)Pt(II)(isonic)(2) (en = ethylenediamine, dmpda = 2,2'-dimethyl-1,3-propanediamine, nic = nicotinate, and isonic = isonicotinate), in aqueous solutions. Equimolar reactions of copper(II) nitrate with (dmpda)Pt(II)(isonic)(2) and (en)Pt(II)(nic)(2) resulted in 1-D ([(dmpda)Pt(isonic)(2)Cu(OH(2))(3)](NO(3))(2))(n)() (1) and 2-D ([(en)Pt(nic)(2)Cu(OH(2))](NO(3))(2))(n) (2), respectively, but the reaction of (en)Pt(II)(nic)(2) with excess copper(II) nitrate gave 3-D ([((en)Pt(nic)(2))(3)Cu(5)(OH)(2)(OH(2))(6)](NO(3))(8))(n) (3). The local structure of crystal 1 has a mononuclear copper unit, 2 has a dinuclear copper unit with a Cu-Cu distance of 2.659(5) A, and 3 has a pentanuclear copper unit. The methyl groups of the dmpda ligand are located in the space between two isonicotinate ligands of 1, which is presumed to be an important factor to determine the final structure of the crystal formed by self-assembly. Magnetic behaviors of crystals 1-3 examined in the temperature range of 4-300 K appear to be governed by the local structures around the copper(II) ions and do not indicate any significant long-range magnetic exchange interactions along the polymeric chain.

The reaction of [Pt(IV)(dach)(OH) 4 ] (dach= trans -(±)-1,2-diaminocyclohexane) with an excess of carboxylic acid at room temperature afforded tricarboxylatoplatinum(IV) complexes, [Pt(dach)(L) 3 (OH)] (L=acetato, propionato, valerato) in contrast to the carboxylation reaction with excess carboxylic anhydrides, which gave only tetracarboxylatoplatinum(IV) complexes as a major product. The protonation on hydroxo ligand of the platinum(IV) complex to form aqua ligand seems to be followed by nucleophilic substitution by carboxylate or chloride anion. Such nucleophilic substitution afforded only partially substituted tricarboxylatoplatinum(IV) complexes in carboxylic acid solvent whereas the reaction in 0.1 M HCl solution gave tetrachloroplatinum(IV) complex. This difference is explainable by different p K a values of the four aqua ligands, among which the last aqua ligand may have sufficiently low p K a value allowing the protonation only in strong acidic media like hydrochloric acid.

Novel trinuclear disilver(I)–copper(II) complexes, [Ag(PPh3)2]2[Cu(mtm)2] (1) and [Ag2(dppm)2][Cu(mtm)2] (2) (mtm=[bis(methylthio)methylene]malonate, dppm=bis(diphenylphosphino)methane) have been prepared and characterized by a single-crystal X-ray structure analysis. In the complex 1, a silver atom is coordinated to each of the two carboxylate oxygens with different bond distances of 2.325(5) A (AgO(1)) and 2.653(6) A (AgO(2)). In the case of the complex 2, two silver atoms are bridged by two dppm ligands separated by 3.0130(9) A and Ag(1) has bonded to O(5) (2.442(5) A). Interestingly, Ag(2) has bonded to O(4) (2.325(5) A) which is not a coordinated carboxylate oxygen bonded to copper(II) atom. Interaction between silver(I)–thioether group was not observed in 1 and 2.

A new series of quinolone-platinum(II) conjugates, [Pt(Q'-NH2)(dmso)X2] and cis-[Pt(Q"-en)X2], where Q' and Q" are quinolones (flumequine, nalidixic acid or oxolinic acid) linked to monodentate and bidentate amine ligands, respectively, and X2 is Cl2 or 1,1-cyclobutanedicarboxylate, have been synthesized with the aim of examining the synergetic antitumor activity of quinolone intercalation and platinum(II) chelation. The complexes were characterized by elemental analyses and IR and multinuclear (1H and 195Pt) NMR spectroscopies, and then subjected to in vitro and in vivo bioassays using the leukemia L1210 cell line.

The hydroxyphenyl chiral ketone, (S)-3, reacts with D-amino acids bearing hydrophobic side chains exclusively over the L-amino acids in a two-phase liquid-liquid extraction, and thus acts as a highly stereoselective extractant. Calculations for the energy-minimized structures for the imine diastereomers and the comparison of the selectivities with other phenyl ketones, (S)-4 and (S)-5, demonstrate that the hydrogen bond between the carboxylate group and the phenolic hydroxyl group contributes to the remarkable enantioselectivities. The multiple hydrogen bonds present in the imine of (S)-3 reinforce the rigidity, and results in the difference between the stabilities of the imine diastereomers. The imine could be hydrolyzed in methanolic HCl solution, and the extraction of the evaporated residues revived the organic layer of (S)-3, which could enter into a new extractive cycle and leaves the D-amino acid with enantiomeric excess (ee) values of over 97 % in the aqueous layer.

Novel acrylamide-based hard-soft hybrid block copolymers generate high-quality nanolithographic patterns satisfying high-resolution, long-range ordering, low defect density, moderate etch selectivity, and easy pattern transfer onto a substrate. The resulting patterns can also be used as a scaffold for metallic nanostructures such as aligned nanowires and nanomeshes with extraordinary structural regularity.

Pale blue crystals were obtained from an aqueous solution containing equimolar amounts of (dmpda)Pt(N-nic) 2 (dmpda=2,2-dimethyl-1,3-propanediamine, nic=nicotinate) and copper(II) nitrate and subjected to X-ray crystallography, which revealed that the crystals are a composite material of the formula [(dmpda)Pt(N-nic) 2 ] 2 ·Cu(OH 2 ) 5 ·2NO 3 ·4.5H 2 O. Copper(II) nitrate was found to be intercalated between the platinum complex layers which were constructed by non-covalent bonding interactions such as hydrogen bonding, π–π* stacking and electrostatic interactions of the platinum(II) complex. A linear array of the intercalated cationic Cu(OH 2 ) 5 complex was observed. The value of the effective magnetic moment of the composite material is subnormal ( μ eff =1.57 BM) at room temperature.

The C2-symmetric bisphosphinobioxazoline [(S,S)-Phos-Biox] 4 was found to be a highly efficient chiral ligand for Pd-catalyzed enantioselective allylic substitution of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate and afforded enantioselectivities of up to 97% ee. Moderate enantioselectivities have been observed in Pd-catalyzed desymmetrizations of cis-1,4-bis(benzoyloxy)cyclopent-2-ene (12) with dimethyl malonate (51−78% yield, 38−58% ee) and N-benzyl-N-methylamine (87% yield, 33% ee) nucleophiles and of biscarbamate 15 of cis-1,4-dihydroxycyclopent-2-ene (90% yield, 50% ee). A 1:1 molar mixture of (S,S)-Phos-Biox 4 with Pd(CH3CN)2Cl2 and [(η3-C3H5)PdCl]2 afforded the P,N,N,P-tetradentate Pd(II) complexes 19a and 19b, respectively. The structures of the complexes 19a,b were determined by X-ray analysis. The complex 19a also exhibited high enantioselectivity (86% yield, 92% ee) in allylic substitution of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate.

Despite the impressive antitumor activity of cisplatin, two major limitations of the drug, that is severe side effects and drug-resistance of cancer cells, make its use difficult for cancer therapy. These limitations have resulted in a great deal of effort having been expended into structural modifications of cisplatin. In this study, we tested two novel cisplatin analogues, (CPA)2Pt [DOLYM] (COMP-I) and (DACH)Pt[DOLYM] (COMP-II), for the mode of cytotoxic action against human tumor cells comparing with cisplatin and carboplatin in vitro. These two novel analogues had considerable cytotoxic activities against five kinds of human solid tumor cells, and especially COMP-II was more effective on HCT15 colon cancer cells than other compounds. In addition, COMP-II had cytostatic activity at low concentrations (10-0.3 microgram/ml), but other compounds revealed little effect on tumor growth at the low concentration.

A novel imidazolium-based binol receptor 4 has been synthesized and used as a chirality conversion reagent for general amino acids with higher d -form selectivity compared to other guanidinium-based receptors. Favorable solubility in chloroform enabled 4 as an effective chiral extractant for the resolution of racemic amino acids.

Studies have been carried out on two solvent-dependent structures of Co(NO3)2 with trans-1,2-bis(4-pyridyl)ethylene (bpee) and their interconversions. X-ray analyses disclose that the molecule obta...

Single crystals of silver(I) and mercury(II) d-lactobionates (LBA) grown from aqueous solutions were subjected to X-ray analysis. Both compounds crystallize in the monoclinic space group C2 (No. 5)...

New zwitterioni (diamine)platinum(II) complexes A2Pt(ita) (A2 = 2,2-dimethyl-1,3-propanediamine (dmpa), tetrahydro-4H-pyran-4,4-diylbis(methylamine) (thpdma), trans-(±)-1,2-diaminocyclohexane (dach), ethylenediamine (en); ita = itaconate) have been synthesized and characterized by means of NMR spectroscopy and X-ray analysis. The platinum atom adopts a square-planar arrangement, in which the itaconate ligand is coordinated to the platinum atom through one carboxylate and the ethylate groups. The ethylene group occupies the fourth coordination site of the square plane, which intersects the midpoint of the CC bond axis, but the bond axis is not perpendicular to the square plane because of i ts chelated ri ng strain. Such a chelation mode is retained without linkage isomerism in aqueous solution up to 70°C.

The reaction of hexachlorocyclotri(λ5-phosphazene), N3P3Cl6, with a series of pyrimidine-2-thiol in the presence of triethylamine in boiling tetrahydrofuran solution affords only a geminal isomer, N3P3(N–S)2Cl4 (N–S = 2-pyrimidinylthio (pms), 4,6-dimethyl-2-pyrimidinylthio (dmpms), and trifluoromethyl-2-pyrimidinylthio (fmpms)) in high yield. The molecular structures of N3P3(pms)2Cl4 (monoclinic P21/n, a = 7.686(2), b = 28.236(7), c = 8.760(2) A, β = 99.87(2)°, V = 1873.2(8) A3, Z = 4, R = 0.052) and N3P3(dmpms)2Cl4 (triclinic , a = 8.698(3), b = 9.630(3), c = 14.179(6) A, α = 100.88(3), β = 92.83(3), γ = 103.84(3)°, V = 1126.9(7) A3, Z = 2, R = 0.049) have been solved. The crystal structures disclose that the nitrogen atom of the 2-pyrimidinylthiol group significantly interacts with the phosphorus atom of the cyclotri(phosphazene) ring within the sum of the van der Waals radii (3.40 A). The P…N intramolecular interaction of N3P3(dmpms)2Cl4 (P(1)–N(5), 3.109(4); P(1)–N(7), 3.126(4) A) is considerably long...