Tadahiro Tetsumi

2-(2,3-Naphthalimino)ethyl trifluoromethanesulphonate as a highly reactive ultraviolet and fluorescent labelling agent for the liquid chromatographic determination of carboxylic acids

Abstract The use of 2-(2,3-naphthalimino)ethyl trifluoromethanesulphonate in the preparation of 2-(2,3-naphthalimino)ethyl ester derivatives of carboxylic acids for ultraviolet and fluorescent detection in high-performance liquid chromatography is described. The reagent is easily synthesized in two steps from 2,3-naphthalenedi-carboxylic anhydride and is stable at least for 6 months at room temperature. Reactions of carboxylate potassium salts (10 −5 M ) with a 10-fold equivalent excess amount of the reagent proceed to completion within 10 min in acetonitrile at room temperature in the presence of 18-crown-6 as a catalyst. The derivatization procedure with this reagent has been applied succesfully to the determination of some carboxylic acids in mouse brain. The detection limits (signal-to-noise ratio = 3) with ultraviolet and fluorescent detection are 100 fmol (at 259 nm) and 4 fmol (λ ex = 259 nm, λ em = 394 nm), respectively.

Separation of racemates by capillary zone electrophoresis based on complexation with cyclodextrins

In this communication, we describe the separation of dansylamino acids or barbiturates in the presence of unmodified or methylated Cyclodextrins

Direct reaction of meta powders with several sodium dithiocarbamates

Abstract Copper and nickel powders react directly with sodium dithiocarbamates in organic solvents and produce the corresponding metal complexes. The rate constants have been estimated spectrohotometrically. The effects of organic solvents and substituents of the carbamates on the relative reactivity were studied. The results show that copper powder reacts in chloroform more readily than any other system examined. This reaction has been successfully applied to the determination of copper contents in brass and bronze powders.

Reaction of copper powder with tetraalkylthiuram disulphides

Abstract Copper powder reacts photochemically with tetraalkylthiuram disulphides [(R 2 NCS 2 ) 2 , TRTD] in chloroform. The effect of different alkyl substituents (R) on the reaction was studied systematically by means of both high-performance liquid chromatography (HPLC) and spectrophotometry. The results obtained show that the reactivity of (R 2 NCS 2 ) 2 increases with increase of R in the order butyl > propyl > ethyl > methyl. In addition, this reaction is applicable to the analysis of the copper content in copper powder, copper oxides, copper(II) hydroxides, and basic copper carbonates.

Crystal and molecular structure of 10,20-epoxy-grayanotoxin-II

The photooxidation with HgO in benzene and the hydrolysis with 2%-KOH in methanol of the grayanotoxin (GTX) derivative (4) gave a 10,20-epoxy-grayanotoxin-II(5). The crystal structure of (5) has been determined by X-ray diffraction at room temperature. The crystal is monoclinic, space group P21, with a = 14.248(10) Å, b = 6.670(10) Å, c = 9.990(10) Å, α = 105.507(8)°, V = 914.9(2) Å3, Z = 2. The structure was solved by direct methods and refined by full-matrix least squares methods to a final R1 = 0.046 (wR2 = 0.0833) for 1161 independent reflections. The molecule has a pentacyclic structure consisting of two five-membered, one six-membered, one seven-membered, and one three-membered rings. The three-membered ring is connected with the seven-membered ring by spiro-type bond.

Crystal and molecular structure of grayanotoxin VII

The crystal and molecular structure of a grayanotoxin VII is presented. The crystal is monoclinic, space group P21, with a = 7.647(1) Å, b = 11.7591(7) Å, c = 10.0873(6) Å, β = 91.143(8)°, V = 906.9(1) Å3, Z = 2. The structure was solved by direct methods and refined by full-matrix least-squares methods to a final R = 0.057 for 1494 independent reflections. The molecule has a tetracyclic structure consisting of two five-membered, one six-membered, and one seven-membered rings.

Crystal and molecular structure of a new diterpenyl glycoside from Pteris cretica L.

The crystal and molecular structure of a new diterpenyl glycoside, Ptr-1, is presented. The crystal is triclinic, space group P1, with a = 8.2414(8) Å, b = 13.0826(9) Å, c = 6.1427(8) Å, α = 95.345(9)°, β = 111.589(8)°, γ = 96.726(7)°, V = 604.9(1) Å3, Z = 1. The structure was solved by direct methods and refined by full-matrix least-squares methods to a final R = 0.049 (Rw = 0.099) for 1872 independent reflections. The molecular structure is based on a glycopyranosyl group and a tetracyclic group. The glycopyranosyl group is β-D-allopyranosyl group. The tetracyclic group consists of 1 five-membered and 3 six-membered rings.

The Synthesis and Properties of Block-Copoly(amino acid)s with Folded Structures: A Primitive Enzyme Model

As a model of a primitive enzyme block-copoly(amino acid)s con taining L-serine and L-aspartic acid as the repeat unit were prepared. Spectro scopic measurements indicate that some block-copoly(amino acid)s, especially ABAB and ABABA types, do form folded conformations. Hydrolysis reactions of p-nitrophenyl p-guanidinobenzoate were accelerated in the presence of ABAB and ABABA type block-copoly(amino acid)s compared with a random copoly (amino acid). From these results we speculate that primitive enzymes were born by assembling block-copoly(amino acid)s.

Reversed-phase ion-interaction chromatography of sodium dialkyldithiocarbamates in the presence of tetralakylammonium salts

Abstract The elution behaviour of sodium dialkyldithiocarbamates (R2NCS2Na: RCH3, C2H5, n-C3H7 and n-C4H9) was examined by high-performance liquid chromatography on C1-, C8- and C18-bonded silica columns in the presence of tetraalkylammonium salts. The best separation of the carbamates was obtained from the C8-bonded column, with a mobile phase of methanol—1/15 M phosphate buffer (60:40) at pH 6.8 containing tetra-n-butylammonium bromide (0.025 M). This method was applied to the analyses of commercial R2NCS2Na. The results are in good agreement with those obtained by potentiometric titration.

Chelate-forming reactions of thiurams and sodium dialkyldithiocarbamates in an ion source of a mass spectrometer

Abstract Tetraalkylthiuram sulfides and sodium dialkyldithiocarbamates reacted with the metals (Fe, Ni, Cr and Cu) present in the ion source of a mass spectrometer to give their metal complexes.