Ryotaro Azuma

Structure and cycloaromatization of a novel enediyne, C-1027 chromophore

Abstract The structure and the cyloaromatization mechanism of a novel enediyne, C-1027 chromophore, were elucidated. The C-1027 chromophore has a 9-membered 1,5-diyn-3-ene core structure in the 16-membered macrocylic ring.

Structure of an aromatization product of C-1027 chromophore

Abstract The structure of an aromatization product of C-1027 chromophore was determined by means of chemical degradation and detailed 2D-NMR studies.

Structure of cypemycin, a new peptide antibiotic

Abstract The structure of cypemycin, a new peptide antibiotic, was determined by means of FAB-MS, NMR, and amino acid analysis. The data have revealed cypemycin as being a structurally unique peptide antibiotic that contains a sulfide bridge at its C-terminus as well as four α,β-unsaturated amino acids.

Simultaneous determination of GTS-21 and its metabolite in rat plasma by high-performance liquid chromatography using solid-phase extraction

It has been suggested that GTS-21 can improve the learning deficits and inhibit the neuro-degeneration in patients with Alzheimers disease. This paper describes a reversed-phase high-performance liquid chromatographic assay with visible detection at 405 nm for determination of GTS-21 and its metabolite, 4-hydroxy-GTS-21 in rat plasma. The method uses solid-phase extraction with a Bond Elut C18 column. A quantitation limit of 1.0 ng/ml was achieved using 0.5 ml of rat plasma. In the validation study, the coefficients of variation and the relative errors of each compound were less than 10%. Also freeze-thaw and storage stability were confirmed. This method has proved to be applicable to the pharmacokinetic study of GTS-21 in rats.

Structure of a novel macrodiolide antibiotic IKD-8344

Abstract A new antitumor antibiotic IKD-8344 produced by an Actinomycete, strain No.8344, was elucidated to have a macrocyclic dilactone structure ( 1 ) on the basis of the spectroscopic evidence.

High-performance liquid chromatographic determination of 6-amidino-2-naphthyl [4-(4,5-dihydro-1H-imidazol-2-yl)amino]benzoate dimethanesulphonate and its metabolites in biological fluids

6-Amidino-2-naphthyl [4-(4,5-dihydro-1H-imidazol-2-yl) amino]benzoate dimethanesulphonate has been developed for the therapy of pancreatitis. A reversed-phase high-performance liquid chromatographic assay of the levels of this drug and its metabolites in biological fluids was investigated. Fluorescence detection with post-column alkaline degradation was used for the determination of the intact drug and the amidinonaphthol moiety metabolite, and ultraviolet detection at 254 nm was used to determine the levels of the benzoic acid moiety metabolite. Satisfactory recoveries and variabilities of the intact drug and its metabolites from biological fluids were obtained. The detection limits for the intact drug and amidinonaphthol were 0.5 ng/ml at a signal-to-noise ratio of 12 in plasma and 10 ng/ml at a signal-to-noise ratio of 32 in urine and homogenized faeces, and those of benzoic acid were 5 ng/ml at a signal-to-noise ratio of 3 in plasma and 50 ng/ml at a signal-to-noise ratio of 7 in urine and homogenized faeces.

Simultaneous determination of a novel anticancer drug, TAS-103, and its N-demethylated metabolite in monkey plasma by high-performance liquid chromatography using solid-phase extraction.

A simple and rapid method for the analysis of a novel anticancer drug, TAS-103, and its metabolite demethyl-TAS-103 in monkey plasma has been developed. This method is based on high-performance liquid chromatography with visible detection at 460 nm after solid-phase extraction with a Sep-Pak Vac PS-2 cartridge. The extraction recoveries of each compound, including the internal standard TAS-1-1018, were from 88 to 102%. The quantitation limit of each compound was 5.0 ng/ml in 0.5 ml of plasma. The coefficients of variation for each compound ranged from 0.9 to 4.9%, and relative errors for each compound ranged from -3.8 to 4.6%. Both compounds in monkey plasma were stable at -80 degrees C for 39 days and the extracts were stable at ambient temperature for 24 h. This method has been demonstrated to be useful for the pharmacokinetic study of TAS-103 in monkey plasma after intravenous administration.