Construction of literature databases for clathrate and inclusion compounds

An attempt to construct the literature databases for inclusion complexes since the beginning of this century is illustrated. The original literatures were cited and cross-checked by several secondary sources including Chemical Abstracts. The existing database systems appear to be insufficient to obtain necessary information efficiently in such a newly and rapidly developing field as inclusion chemistry. The trends in research revealed in the course of the database construction are analyzed and discussed for some important categories of inclusion chemistry.     

Absolute helical arrangement of sulfonamide in the crystal

[reaction: see text] 1,2-Bis(N-benzenesulfonyl-N-methylamino)benzene (2), which has no fixed asymmetric element, was crystallized from ethyl acetate as chiral crystals belonging to space group P4(1)2(1)2 (No. 92) or P4(3)2(1)2 (No. 96). The array of molecules built by the CH-pi interaction along the c-axis forms an enantiomeric helical superstructure in each individual crystal. The absolute configurations of the chiral crystals of 2 were determined by X-ray crystal structure analysis using the Flack parameter method. The solid-state CD spectra of the chiral crystals in KBr were mirror images. The equilibrium between the two enantiomers in solution is fast during crystallization at ambient temperature, and the energy barrier (DeltaG()) is estimated to be 11.7 +/- 0.3 kcal/mol (233 K).     

Potentiometric flow injection analysis of concentrated hydrogen peroxide by using an Fe(II)-Fe(III) redox potential buffer solution

The flow injection analysis of hydrogen peroxide is proposed, using a redox electrode and an Fe(II)-Fe(III) potential buffer solution. Influencing factors, such as the concentrations of Fe(II)-Fe(III) and sulfuric acid in the potential buffer on sensitivity of the proposed method are examined. The analysis of high concentrations of hydrogen peroxide up to approximately 10 M was conducted successfully with relative standard deviation of 0.7%.     

Solubilization of steviolbioside and steviolmonoside with gamma-cyclodextrin and its application to selective syntheses of better sweet glycosides from stevioside and rubusoside

1,4-alpha-Glucosylation at the 13-O-glycosyl moiety of stevioside (S) and rubusoside (RU) results in a significant increase of sweetness. Saponification of the 19-COO-beta-glucosyl linkage of S and RU yielded steviolbioside (SB) (= 13-O-beta-sophorosyl-steviol) and steviolmonoside (SM) (= 13-O-beta-glucosyl-steviol), respectively, both of which are poorly soluble in an acetate buffer. It was found that the solubilities of SM and SB in the buffer solution were remarkably increased in the presence of gamma-cyclodextrin (gamma-CD). SB was solubilized in the buffer solution with the aid of gamma-CD, and the solution was subjected to 1,4-alpha-transglucosylation by using a cyclodextrin glucanotransferase-starch system to give a mixture of products which were glucosylated at the 13-O-glycosyl moiety. This mixture was acetylated, and the acetate was subjected to chemical beta-glucosylation of 19-COOH followed by deacetylation to afford compounds which have superior sweetness to S. In the same way, derivatives with superior sweetness were selectively prepared from RU through SM.     

Cussosaponins A-E,triterpene saponins from the leaves of Cussonia racemosa,a Malagasy endemic plant

Five new triterpene saponins, cussosaponins A (2), B (3), C (4), D (5), and E (6), were isolated from the dried leaves of Cussonia racemosa BAKER. The structures of these new compounds were deduced on the basis of chemical and spectroscopic evidence.     

Resorufin as an electron acceptor in glucose oxidase-catalyzed oxidation of glucose

Resorufin (1) has been found to act as an electron acceptor in glucose oxidase (GOD)-catalyzed oxidation of glucose. When a 1: 1: 1 mixture of solutions of 1 (5.0 microM), glucose, and GOD (4.0 mg/ml) in phosphate buffer (pH 7.4, 0.1 M) was incubated at 36 degrees C under aerobic conditions and the reaction was followed by a measurement of changes in fluorescence intensity due to 1, only two types of fluorometric traces were observed: (1) when a glucose solution of less than 0.7 mM was subjected to the enzymatic reaction, no consumption of 1 was observed; (2) the reaction with glucose at more than 1.0 mM always consumed 1, affording a regression fluorometric curve, and yet the obtained fluorometric traces could be almost superimposed on one another with no dependence on the glucose concentration. The reasons for the observed phenomena are discussed.     

A kinetic and thermodynamic study on hydrolysis of sodium laurate in aqueous phase accompanied by transfer into oil phases containing different organic additives (I)

The kinetic and thermodynamic behavior at the interface between an aqueous solution of sodium laurate (NaLA) and various oil phases comprised primarily of benzene (Bz) and/or different organic compounds including amphiphiles has been investigated in regard to the hydrolysis of NaLA accelerated at the interface, transfer of lauric acid (LA) into oil phase and reverse transfer of Bz into aqueous phase in addition to interface tension. The contact of aqueous NaLA solution with the oil phase was found to accompany the mass transfer of LA and simultaneously promote the hydrolysis of NaLA in water phase. Analysis of the change of OH⁻ ion concentration ([OH⁻]) over time allowed us to treat the events as a first order reaction. From the rate constant data the activation parameters such as the activation enthalpy and entropy, both of which control the transfer of LA molecules, were determined. The parameters were found to depend greatly on varied situations of the oil phase, being clearly able to explain the physicochemical behavior of the interface. Comparing the cases where the oil phase is one of the respective single systems such as Bz, dodecane (C₁₂) and dodecylbenzene (C₁₂Bz), C₁₂Bz resulted in the lowest rate constant. The transfer (or hydrolysis) rate was measured for the amphiphile-added oil systems as a function of amphiphile concentration. When 0.206 M C₁₆OHBz came in contact with aqueous phase, emulsion formation at the interface layer was brought about with approximately zero activation enthalpy, leading to facile or spontaneous transfer of LA. In addition, UV absorbance representing the transfer of Bz from the oil phase to the aqueous phase also demonstrated the effects of added amphiphiles on the action of the interface.     

Manganese(II) complexes with edta-type ligands. The molecular structure of aquo-dihydrogen(1,2-propanediamine-N,N,N′,N′-tetraacetate)manganese(II) trihydrate, [Mn(H21,2-pdta)(H2O)] · 3H2O

New manganese(II) complexes with ethylenediamine-N,N,N,N-tetra-3-propionate (edtp) and 1,2-propanediamine-N,N,N,N-tetraacetate (1,2-pdta) were prepared and characterized by elemental analysis, i.r. spectroscopy and magnetic measurements. The structure of [Mn(H₂1,2-pdta)(H₂O] · 3H₂O was determined by the single crystal X-ray diffraction technique. The complex crystallizes in the space group P2₁/n(#14) of the monoclinic crystal system with unit cell parameters a = 10.993(2) Å, b = 14.092(2) Å, c = 11.753(1) Å, = 96.302(9)⁰, V = 1809.7(3) ų, Z = 4 and R = 0.051. The complex contains seven-coordinated Mn^II ion with H₂1,2-pdta ion acting as hexadentate ligand and one water molecule.     

Identification of the metal ion binding site on an RNA motif from hammerhead ribozymes using (15)N NMR spectroscopy

An RNA oligomer, r(GGACGAGUCC), which mimics the metal ion-binding motif of hammerhead ribozymes, was shown to fold by itself into a conformation possessing a metal ion binding property which is similar to that of the intact ribozyme (Tanaka, et al. J. Am. Chem. Soc. 2000, 122, 11303-11310). To determine the metal ion-binding site of this motif at an atomic level, we synthesized a series of RNA oligomers which were selectively labeled with a (15)N-labeled guanosine at each of the four guanosine residues. The (15)N-chemical shift perturbation with Cd(II) ions by one-dimensional (1D) (15)N NMR spectra showed that the chemical shift of the N7 of the G7 residue, N7/G7, in the metal ion-binding motif was specifically perturbed. This is the first experimental evidence to prove that the N7/G7 binds with a Cd(II) ion.