New Strategy for Synthesis of the Disaccharide Moiety of the Highly Potent Anticancer Natural Product OSW-1
摘要:
The facile synthesis of a partially protected OSW-1 disaccharide moiety, having a 2-O-p-methoxybenzoyl-beta-D-xylopyranosyl-(1 -> 3)-2-O-acetyl-L-arabinopyranoside structure, was elaborated by glycosylation in a beta-stereoselective fashion. The xylopyranose donors were synthesized by a short synthetic approach via convenient selective 1,2-diacetal protection of 3,4-trans-diequatorial hydroxyl group. Regioselective ring opening of 1,2-diacetal-protected substrates efficiently led to the arabinopyranose acceptor with a free 3-hydroxyl group. Glycosylation of the xylopyranose donor with the arabinopyranose acceptor provided the beta-disaccharide.
Stereoselective acetylation of hemicellulosic C5-sugars
作者:Zachary D. Herde、Prathap D. John、Dania Alvarez-Fonseca、Jagannadh Satyavolu、Christopher T. Burns
DOI:10.1016/j.carres.2017.03.008
日期:2017.4
dimethylaminopyridine (DMAP) is described. The peracetylated d-xylose and l-arabinose alpha pyranose anomers 2α and 5α are obtained in 97% and 56% yields respectively. The peracetylated d-xylose beta pyranose anomer 2β is obtained in 71% yield through simple modification of the reaction conditions. Details regarding synthesis and isolation optimization studies under different conditions are presented below
Various 5'-β-saccharides of pyridoxine, namely the mannoside, galactoside, arabinoside, maltoside, cellobioside and glucuronide, were synthesized chemically according to Koenigs-Knorr conditions using α4,3-O-isopropylidene pyridoxine and the respective acetobromo glycosyl donors with AgOTf (3.0 eq.) and NIS (3.0 eq.) as promoters at 0 °C. Furthermore, 5'-β-[13C6]-labeled pyridoxine glucoside (PNG)
Seven second-generation hypoxic markers of the iodinated azomycin nucleoside class have been synthesized and tested for hypoxia marking activity with tumor cells in vitro and in vivo. β-D-lodoazomycin galactoside (IAZG) and β-D-iodoazomycin xylopyranoside (IAZXP) demonstrated superior hypoxia marking properties relative to IAZA because of their higher water solubilities, rapid plasma clearance rates
active site of the enzyme and that quite bulky aglycons are accepted. By separating the aromatic aglycon from the xylose moiety by linkers, a trend towards increased galactosylation with increased linker length is observed. The galactosylation is influenced by the identity and position of substituents in the aromatic framework, and generally, only xylosides with beta-glycosidic linkages function as good
作者:Lisa M. Doyle、Shane O’Sullivan、Claudia Di Salvo、Michelle McKinney、Patrick McArdle、Paul V. Murphy
DOI:10.1021/acs.orglett.7b02760
日期:2017.11.3
Glycosyl thiols are widely used in stereoselective S-glycoside synthesis. Their epimerization from 1,2-trans to 1,2-cis thiols (e.g., equatorial to axial epimerization in thioglucopyranose) was attained using TiCl4, while SnCl4 promoted their axial-to-equatorial epimerization. The method included application for stereoselective β-d-manno- and β-l-rhamnopyranosyl thiol formation. Complex formation explains