Structures of minor components of the validamycin complex.
complicated oligosaccharides using NMRspectroscopy have developed quite remarkably. The structure of validamycin G (VM-G),43 the most recently discovered congener was established by making use of these techniques. Wehave now used NMRto reinvestigated the position of the glycosidic linkage of the minor components which had remained obscure. The results were first disclosed in a patent application,53 though without experimental data. Here we discussed the structures of the minor components with experimental results. To elucidate the unidentified positions of the glucosidic linkage by *H NMRspectroscopy, VM-B~ F were acetylated with acetic anhydride and pyridine to give the corresponding peracetyl derivatives. The chemical shifts of 1-H and l'-H of the peracetates, recognized in the region of 3.2~3.6 ppm, indicate that the imino group is not acetylated. Therefore, these peracetates must be dodeca-O-acetyl validamycin B (Ac-
Synthetic studies on antibiotic validamycins. Part 14. Total synthesis of (+)-validamycins C, D and F
(+)-Validamycins C and F were first completely synthesised by use of a common blocked derivative 5 of (+)-validoxylamine A. The diols 6 and 7, obtained by acid hydrolysis of 5, were appropriately protected to give the aglycones 17, 25 and 30, which were condensed with glycosyl donor 11 or 19 to afford the condensates 20 and 26, being convertible, by deprotection and acetylation, to the totally O-acetylated derivates 21 and 33 of validamycins C and F, respectively. In addition, (+)-validamycin D was first synthesised by α-glycosylation of the protected derivative 37 of validoxylamine A.
Chemical constituents and chemotaxonomic study of Glycyrrhiza pallidiflora maxim
Abstract Phytochemical study of Glycyrrhiza pallidiflora Maxim. gave seventeen compounds, including two sterols (3 and 4), four triterpenes (1, 2, 5, 6), ten flavones (7, 9–17), and one pterocarpan (8). The chemotaxonomic significance of G. pallidiflora was discussed, which indicated the close relationship between G. pallidiflora with other species of Glycyrrhiza. Moreover, pallidiflorin can be served as a fingerprint for G. pallidiflora, macedonic acid and echinatin can be recognized as biomarkers for Glycyrrhiza, while formononetin, afrormosin and calycosin may be typical second metabolites for Papilionoideae.