Kenji Mizutani

13C nmr study of α- and β-anomeric pairs of d-mannopyranosides and l-rhamnopyranosides

Abstract 13C NMR spectra for a variety of α and β-anomeric series of d -mannopyranosides and l -rhamnopyranosides are presented and analyzed in comparison with those of D-glucopyranosides. The results obtained in the present study are valuable for the structure studies of plant-glycosides as well as carbohydrates, especially for determination of anomeric configurations of mannosides and rhamnosides which has been extremely difficult by other classical techniques.

N.m.r. spectral study of α- and β-l-arabinofuranosides☆

Abstract Anomeric pairs of l -arabinofuranosides of various aliphatic alcohols were synthesized and then investigated by n.m.r. spectroscopy. The 13 C-n.m.r. glycosylation shift of these l -arabinofuranosides is very similar to that of l -arabinopyranosides and other glycopyranosides reported previously. The 3 J H-1,H-2 value of these α- l -arabinofuranosides is significantly different from that of the β anomers and can be used for the determination of the anomeric configuration. However, in contrast to the case of glycopyranosides, the 1 J C-1,H-1 values of each anomeric series of l -arabinofuranosides are very similar to each other. Some disaccharides containing an l -arabinofuranoside unit were also investigated by n.m.r. spectroscopy.

Eurycomanone and eurycomanol, quassinoids from the roots of Eurycoma longifolia

Abstract From the roots of Eurycoma longifolia , used as an Indonesian folk medicine, two highly oxygenated quassinoids, named eurycomanone and eurycomanol were isolated. The structures of both new bitter principles were elucidated by NMR, MS, UV and IR.

13C-N.M.R. Spectroscopy of α- and β-anomeric series of alkyl l-arabinopyranosides

Abstract Anomeric pairs of l -arabinopyranosides of a variety of aliphatic alcohols were prepared, and their n.m.r. spectroscopy, especially the glycosylation shift of their 13 C signals, was investigated in comparison with those of d -glucopyranosides, d -mannopyranosides, and l -rhamnopyranosides reported previously. It was found that the glycosylation shift of the l -arabinopyranosides in the present study is almost the same as that of d -glucopyranosides, and the conformational equilibrium of each of these l -arabinopyranosides is very similar to that of the corresponding anomer of methyl l -arabinopyranoside, namely, a preponderance of the 4 C 1 , form, regardless of the structure of the aglycon alcohol. The present results are also useful for structural study of naturally occurring arabinopyranosides.

Selective cleavage of ester type glycoside-linkages and its application to structure determination of natural oligoglycosides

Abstract On treatment with anhydrous LiI, 2,6-lutidine and anhydrous methanol, an ester type glycosyl linkage of acidic tri- and di-terpenes was selectively cleaved without decomposition of a reducing terminal of the resulting sugar moiety to give an anomeric mixture of methyl glycosides along with an aglycone or a pro-aglycone in quantitative yield. In this reaction, no hydrolysis of any other glycoside linkages took place.

N.M.R.-spectral studies of 2-linked glycosides: 2-O-glycosylation shifts of 2-O-glycosylated α- and β-l-arabinopyranosides

Abstract Anomalous glycosylation shift values of the signals for C-1 (the anomeric carbon atom) and C-2 (the glycosyloxylated carbon atom) were sometimes observed for 2- O -β- d -glycopyranosyl (or -β- d -xylopyranosyl)-β- d -glucopyranosides, whereas no remarkable displacements of the other sugar-carbon signals were observed in these cases. This can be explained in terms of change of the orientation of the glycosyl linkages, owing to strong, steric interaction between the 2- O -glycosyl group and the 1- O -aglycon (or -sugar) group. Various 2- O -glycosylated α- and β- l -arabinopyranosides were synthesized. In the case of α- l -arabinopyranosides, the processes of 2- O -β- d -glucosylation, -β- d -xylosylation, and -α- l -arabinosylation resulted in unexpected, upfield shifts of the C-3, -4, and -5 signals, together with displacement of the C-1 and -2 resonances. Furthermore, significant alteration of the values of 3 J H1,H2 and 1 J C1,H1 was also observed for the 2- O -glycosylated α- l -arabinopyranoside moiety, indicating an increase in the contribution of the 1 C 4 conformation of the glycosylated α- l -arabinopyranoside in these cases. On the other hand, no remarkable variation in the signals of C-3, -4, and -5, or in the 3 J H1,H2 and 1 J C1,H1 values, was found for 2- O -α- l -rhamnosylation, except for 4-epihederagenin-3-yl 2- O -α- l -rhamnopyranosyl-α- l -arabinopyranoside. In the present study, such unusual 2- O -glycosylation shifts were not encountered for the 2- O -glycosylation of β- l -arabinopyranosides.

Revision of configuration of the 12-hydroxyl group of eurycomanone and eurycomanol, quassinoids from eurycoma longifolia

Abstract As a result of the recent structural revision of ailanthone, the configuration of the 12-hydroxyl group of eurycomanone and eruycomanol has been amended to be α.

Acyclic sesquiterpene oligoglycosides from pericarps of Sapindus delavayi

Abstract From pericarps of Sapindus delavayi , new acyclic sesquiterpene oligoglycosides named pyishauosides Ib, IIb, IIIa, IVa and IVb were isolated and the structure of these glycosides was elucidated. A remarkable solubilizing effects on saponin A, geraniol, farnesol and dl -α-tocopherol in water were observed for pyishiauoside IIIA and IVa.

Trifolioside II, an acyclic sesquiterpene oligoglycoside from pericarps of Sapindus trifoliatus

Abstract New acyclic sesquiterpene oligoglycoside named trifolioside II was isolated from pericarps of Sapindus trifoliatus along with two known saponins, and the structure of trifolioside II was elucidated.