Masami Sawada

The crystal structure of cycloinulohexaose produced from inulin by cycloinulo-oligosaccharide fructanotransferase

Abstract The crystal of cycloinulohexaose trihydrate, C 36 H 60 O 30 ·3H 2 O, is trigonal, space group R 3, with unit-cell dimensions a = 24.688 (17), c = 6.477 (3) A for a hexagonal cell, Z = 3. The molecule, which consists of six (2 → 1)-linked β- d -fructofuranose residues, has C 3 symmetry. The conformations of two d -fructofuranosyl moieties in an asymmetric unit are 4 T 3 with P = 348.1° and τ m = 38.9° for Fl, and 4 T 3 with P = 350.5° and τ m = 41.2° for F2. The conformations of OCH 2 CO in the 18-crown-6-ring are gauche - for O-1−C-1−C-2−O-1′ (+ 52.3°) and trans for O-1−C-1′−C-2′−O-1 (+ 163.4°).

Crystal structure of di-β-d-fructofuranose 2′, 1:2,3′-dianhydride

Abstract The crystals of di-β- d -fructofuranose 2′,1:2,3′-dianhydride are monoclinic, space group P 2 1 , with unit-cell dimensions a = 12.8557(14), b = 7.7266(7), c = 7.0322(9)A, β = 97.395(10)°, z = 2. The structure was solved by the direct method, and refined to an R value of 0.046 and an R w value of 0.048 for 2123 observed reflections. The conformations of the furanose rings are 2 E with P = 302.5° and τ m = 39.4° for d -fructose 1, and 3 T 2 with P = 145.7° and τ m = 35.8° for d -fructose 2. The fused, 1,4-dioxane ring has a chair conformation with Cremer-Pople puckering parameters Q = 0.501 A and θ = 8.1°.

Synthesis and structure of planar-chiral (1,2,4-trisubstituted cyclopentadienyl) cobalt(tetraarylcyclobutadiene) complexes containing three different chiralities in one molecule☆

Abstract The first diastereomerically pure planar-chiral cyclopentadienyl-cobalt complexes ( 4 and 5 ) have been synthesised by the reaction of CoCl(PPh 3 ) 3 with a trisubstituted cyclopentadienyl anion having a (−)-menthyl group in the presence of diarylacetylenes. Removal of the menthyl group from 4a and 5a afforded the first optically pure enantiomers of planar-chiral cyclopentadienylcobalt complexes, (+)- and (−)- 6 , and (+)- and (−)- 7 . The molecular structure including absolute configuration of 4a has been established by a single-crystal X-ray structure analysis. Crystallographic data for 4a : orthorhombic, space group P 2 1 2 1 2 1 ; a = 18.602(10), b = 15.629(3), c = 13.893(3) A; Z = 4; R = 0.051, R w = 0.057. The structure of 4a indicates that there exist three different chiralities [planar (Cp′-Co moiety), central ((−)-menthyl group), and helical (C 4 Ar 4 -moiety) chiralityl in one molecule. These complexes provide not only the first optically pure planar-chiral Cp′-Co complexes but also the first examples containing three different chiralities in one molecule.

Depression of the apparent chiral recognition ability obtained in the host-guest complexation systems by electrospray and nano-electrospray ionization mass spectrometry.

Chiral recognition in the host–guest complexation systems of chiral crown ether hosts and amino ester guests was thoroughly examined using the electrospray ionization (ESI) mass spectrometry/enantiomer labeled (EL)-guest method. In this method, the mass spectra of a mixture of three components in a solution, a chiral host (H), an equal amount of an (S)-enantiomer guest labeled with deuterium atoms (GS-dn+) and an unlabeled (R)-enantiomer guest (G R +), were measured and the relative peak intensity value [I(H+G R )+ / I(H + GS-dn)+=IRIS] of the host–guest complex ions, observed with an excess guest concentration, was taken to provide the chiral recognition ability of the host. In our earlier report (1996), we demonstrated that the apparent chiral recognition abilities using a mass spectrometer with a homemade ESI interface were depressed by about one tenth compared with the corresponding abilities obtained by fast-atom bombardment (FAB) MS. In the present study, the enantioselective complexation behaviors of various combinations of chiral crown hosts with chiral guests were further investigated in detail mainly using a modern commercial ESI/ion trap (IT) mass spectrometer. Consequently, it was found that the apparent IRIS values from the ESI-MS/EL-guest method changed significantly, depending upon the instrument used, and in particular, upon the ESI interfaces. Moreover, under the specific measuring conditions in ESI-IT-MS, the degrees of depression of the apparent chiral recognition abilities are roughly grouped into three classes, depending upon the number (or probably the type) of the hydrophobic substituents of the hosts. Representing the degrees by the slopes when plotting the apparent IRIS values in ESI-MS versus those in FAB-MS, the slopes for the three classes are (1) 1.0, (2) 0.7 and (3) 0.3; the higher the hydrophobicity of the hosts (and then, the host–guest complex ions), the lower the slope (the apparent enantioselectivity). Strengthening the degree of depression may be caused by an increase in the local concentration of the host close to the surface of the droplets produced during the electrospary ionization process. The chiral recognition ability (KR/KS) in an equilibrated solution agrees quite well with the IRIS value in FAB-MS rather than that in ESI-MS.

Synthesis of 29,29,30,30-tetracyanobianthraquinodimethane

29,29,30,30-Tetracyanobianthraquinodimethane (TBAQ) was prepared by the reaction of bianthrone with malononitrile in pyridine and its structure and properties were described.

Facile ee-determination from a single measurement by fast atom bombardment mass spectrometry: a double labeling method

Abstract From a single fast atom bombardment mass spectrum, the optical purity (enantiomeric excess: ee ) of chiral organic primary and secondary amine salts (guests) such as tryptophan 2-propyl ester hydrochloride and proline 2-propyl ester hydrochloride was easily determined with a high accuracy using both the deuterium-labeled/unlabeled enantiomeric host pair (DD-Gal2deg and LL-Gal2deg-d 24 ) and the corresponding deuterium-labeled internal standard guest (for example, the S -amino acid ester-d m salt).

Combinatorial evaluation of the chiral discrimination of permethylated carbohydrates using fast-atom bombardment mass spectrometry

The chiral discrimination abilities of several variously permethylated carbohydrates toward various amino acid 2-propyl esters were combinatorially evaluated from the relative peak intensity of the 1:1 diastereomeric complex ions with the deuterium-labeled L-amino acid 2-propyl ester protonated ion and with the unlabeled D-amino acid 2-propyl ester protonated ions in FAB mass spectrometry. The chiral discrimination abilities evaluated using FAB mass spectrometry approximately corresponded to the ratio of the association constants (K(R)/K(S)) toward each enantiomer in the solution. Therefore, this evaluation method is very useful for the screening of the chiral discrimination abilities of carbohydrates and their derivatives.

Chiral recognition in molecular complexation for the crown ether–amino ester system. A facile FAB mass spectrometric approach

Various degrees of chiral recognition properties of chiral crown ether hosts toward amino acid ester guests are directly, easily and reliably evaluated by the enantiomer deuterium-labelled racemic guest method using conventional FAB mass spectrometry.

Caffeoyltryptophan from green robusta coffee beans

Abstract A new compound, caffeoyltryptophan, was isolated from the coffee beans Coffea canephora and its structure was determined by FD mass, IR and 1 H NMR spectroscopy.

Chiral discrimination of permethylated gluco-oligosaccharide toward amino acid ester salts

The chiral discrimination ability of permethylated glucopyrano-oligosaccharides toward amino acid 2-propyl ester hydrochlorides was evaluated using FAB mass spectrometry. In the given permethylated homo-oligosaccharides, permethylated β-cello-oligosaccharide series (II) showed remarkably higher S-selectivity toward tryptophan ester salts (Trp-O-iPr+) independent of the numbers (n) of the glucopyranose unit (n=2–5). The hexamer and heptamer of the permethylated β-malto-oligosaccharide series (I) showed the very similar enantioselectivity to permethylated α- and β-cyclodextrin.