Haruo Ogura

Sterol glucosides from Prunella vulgaris

Abstract The 1H and 13C NMR spectra of sitosterol, stigmasterol, stigmast-7-en-3β-ol and spinasterol have been unambiguously assigned by use of HOMCOR and HETCOR techniqeus. The extensive application of these results leads to the direct identification of a mixture of the four β- d -glucopyranosides of the sterols, which were obtained from Prunelia vulgaris.

Determination of mono-O-acetylated N-acetylneuraminic acids in human and rat sera by fluorometric high-performance liquid chromatography

A simple, rapid, and highly sensitive fluorometric high-performance liquid chromatographic method for the determination of N-acetylneuraminic acid and its mono-O-acetyl derivatives in human and rat sera is described. The neuraminic acids, released by hydrolysis of serum in 2 M acetic acid, are converted with 1,2-diamino-4,5-methylenedioxybenzene, a fluorogenic reagent for alpha-keto acids, to highly fluorescent derivatives without the occurrence of O-acetyl migration and de-O-acetylation. The derivatives are separated isocratically within 25 min by reversed-phase chromatography using a TSK gel ODS-120T column. The limits of detection are 57-192 fmol in a 10-microliters injection volume at a signal-to-noise ratio of 3. This sensitivity permits precise determination of the neuraminic acids in 5 microliters of human and rat sera.

Reversed-phase liquid chromatographic resolution of amino acid enantiomers by derivatization with 2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl isothiocyanate

Abstract A novel method for reversed-phase high-performance liquid chromatographic resolution of amino acid enantiomers by the formation of diastereomers using a new chiral reagent, 2,3,46-tetra-O-acetyl-β- d -glucopyranosyl isothiocyanate (GITC), is described. GITC reacts readily with enantiomeric amino acids at room temperature and the reaction mixture can directly be injected into the chromatograph. The derivatives were detected spectrophotometrically at 250 nm. Complete resolutions were observed for all enantiomers examined o a reversed-phase column eluted with aqueous methanol.

Configurational studies on hydroxy groups at C-2,3 and 23 or 24 of oleanene and ursene-type triterpenes by NMR spectroscopy☆

Abstract Configurational determination of 2,3-dihydroxy and 2,3,23- and 2,3,24-trihydroxy substituents in triterpenoids by 1 H NMR spectroscopy can be unambiguously carried out by analysing signal peaks of the protons on oxygen-bearing carbon atoms. The application of our results leads to the revision of a few triterpene structures previously reported.

Triterpenoids from Prunella vulgaris

Abstract Besides two sterols and three ursane and four oleane triterpenes already known, a new triterpene, 2α,3α,24-trihydroxyolean-12-en-28-oic acid has been isolated from the leaves and stems of Prunella vulgaris. 1H and 13C NMR assignments are given for ring A hydroxylated triterpenes.

Amino acid analysis by reversed-phase high-performance liquid chromatography : Automatic pre-column derivatization with activated carbamate reagent

Succinimido alpha-naphthylcarbamate, an activated carbamate reagent, facilitated the simple and rapid pre-column derivatization of amino acids for fluorimetric detection. The method is based on the formation of naphthylcarbamyl derivatives of amino acids. The carbamylation of amino acids is completed within 1 min at room temperature, and the reaction mixture can be injected directly into a liquid chromatograph equipped with an octadecylsilyl reversed-phase column. The effluent stream is monitored fluorimetrically at 370 nm excited at 290 nm at the sub-picomole level. Naphthylcarbamyl derivatives of common protein amino acids were separated within 30 min by gradient elution with aqueous sodium acetate and acetonitrile. Excess of the reagent does not interfere with the analysis of amino acids, because it is hydrolysed in 2-3 min to give naphthylamine, which is more strongly retained than any amino acid derivatives.

A novel active ester synthesis reagent (N,N′-disuccinimidyl carbonate)

Abstract A convenient reagent for active ester synthesis --N,N′-disucinimidyl carbonate-- was prepared. This reagent was useful for the preparation of active esters and peptides in stead of dicyclohexylcarbodiimide.

Pentacyclic triterpenoids from Prunella vulgaris

Abstract Three new pentacyclic triterpenes together with several known triterpenes have been isolated as their methyl esters from the roots of Prunella vulgaris.

Synthesis of 9-O-acyl- and 4-O-acetyl-sialic acids☆

Various 9-O-acyl derivatives of N-acetyl- and N-glycoloyl-neuraminic acid, and O-(5-acetamido-3,5-dideoxy-D-glycero-alpha- and beta-D-galacto-2-nonulopyranosylonic acid)-(2----6)-O-beta-D-galactopyranosyl-(1----4)-D-glucopyranose were regioselectively synthesized by use of ortho esters. In addition, 5-acetamido-4-O-acetyl-D-glycero-D-galacto-2-nonulopyranosonic acid was prepared starting from the benzyl and methyl esters of N-acetylneuraminic acid.

A convenient synthesis of peptide using oxallates

Abstract The equimolar reactions of N-protected amino acids, amino acids or amino acid esters with oxallates (1a-1e) having active ester groups in the presence of pyridine in acetonitrile afforded the corresponding dipeptides via active esters in good yields.