Osamu Kamo

Entada saponin-III, a saponin isolated from the bark of Entada phaseoloides

Abstract The structure of Entada saponin (ES)-III, one of the main saponins of Entada phaseoloides bark, was established to be 3- O -[β- d -xylopyranosyl (1 → 2)-α- l -arabinopyranosyl (1 → 6)] [β- l -glucopyranosyl (1 → 4)]-2-acetamido-2-deoxy-β- l -glucopyranosyl-28- O -[β- l -apiofuranosyl (1 → 3)-β- d -xylopyranosyl (1 → 2)] [(2- O -acetoxyl)-β- d -glucopyranosyl-(1 → 4)] (6 − O ( R ) (−)2,6-dimethyl-2- trans -2,7-octadienoyl)-β- d -glucopyranosyl echinocystic acid.

Applications in one-dimensional and two-dimensional NMR of a pseudofilter by Jittered time averaging

Abstract The pseudofilter is a new instrumental concept which fills a gap between real and digital filters. The idea was originally motivated by the desire to develop frequency filters in the direction of ω1(f1) in 2D NMR. The filter mechanism relies strictly on the accumulation of repeated coherent signals; therefore only the sensitivity gain results without reduction of noise. Applications are (1) a 2D filter to cut unnecessary time-domain signals, (2) a J filter in 13C-1H shift correlation, and (3) an ideal filter in 1 D and 2D NMR.

Chirality effects on 1H and 13C NMR chemical shifts for Aerosol OT in reverse micelles assisted by line shape simulations and two-dimensional pulse techniques

Abstract For the 1 H NMR spectrum of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in C 6 D 6 D 2 O, the very complex H3′ signals, which have not yet been elucidated, have now been successfully explained by superimposition of the four AB parts, and have been discussed in connection with the diastereoisomers arising from the three asymmetric carbon atoms. Discussion of the 13 C NMR signal assignment of AOT in organic solvents has previously been focused on the signals of the head group (CH(SO − 3 )CH 2 ) and on the CH 2 OCO and OCH 2 CH segments. In this study, the signals arising from the other segments of the two chains have been completely assigned to the individual carbon atoms of each 2-ethylhexyl chain, using pulse techniques. The secondary splitting of the 13 C chemical shifts was due to the chirality effect of an AOT molecule. In particular, the effect of the chiral centers was found to be concentrated on the α chain and to reach the C6′carbon.

Conformation of the polar part in the AOT inverted micelles. Gadolinium ion-induced spin-lattice relaxation studies

Abstract The effect of the addition of H 2 O and D 2 O on the 13 C spin-lattice relaxation times T 1 of Aerosol OT (AOT) was studied in the reversed micellar systems of AOT-benzene. The results show that the interaction of the carbonyl carbon of the -CH 2 COO- group with water is stronger than that of the carbonyl carbon adjacent to the methine. The Gd-induced 13 C and 1 H T 1 values were also measured for the systems of the AOT-benzene and water-solubilized AOT-benzene. The change of molecular conformation of AOT-Gd complexes by the addition of water was discussed based on the results of the Gd-induced T 1 data.

Characterization of the complex formation of 1,6‐anhydro‐β‐maltotriose with potassium using 1H and 39K NMR spectroscopy

The 1H and 39K longitudinal relaxation times (T1) and 1H diffusion coefficients were measured to investigate the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. Although the 1H‐T1 values of H3′, H5′, H1″ and H4″ decreased in the presence of potassium ions, 1H chemical shifts and 1H diffusion coefficients did not show significant changes. The long‐range coupling constants of 3JC−H around the glycosyl bonds did not show significant changes either. In the measurements of 39K spectra, the 39K signal obviously broadened and the 39K‐T1 values decreased in the presence of 1,6‐anhydro‐β‐maltotriose, indicating the complex formation of 1,6‐anhydro‐β‐maltotriose and potassium ions. These results indicate that the conformation and molecular volume were unaffected in the complex formation. Copyright