Electron-deficient pyridinium salts/thiourea cooperative catalyzed O-glycosylation via activation of O-glycosyl trichloroacetimidate donors

• Mukta Shaw,
• Yogesh Kumar,
• Rima Thakur and
• Amit Kumar

Beilstein J. Org. Chem. 2017, 13, 2385–2395, doi:10.3762/bjoc.13.236

• , the optimized method is also utilized for the regioselective O-glycosylation by using a partially protected acceptor. Keywords: cooperative catalysis; electron-deficient pyridinium salts; O-glycoside; regioselectivity; thiourea; Introduction The glycosidic linkage is the principal bond present in a

• with phosphorus acids) for stereoselective O-glycoside bond formation [30]. Similarly, Galan et al. reported a method for the preparation of 2-deoxyglycosides from glycals under the influence of cooperative catalysis (chiral phosphoric acids/thiourea derivatives) [31]. Encouraged by these reports and

• acceptor 2a in 1:1.1 molar ratio with 10 mol % of 3a in dry DCM at room temperature, the desired O-glycoside 5a was isolated in 56% yield and with poor selectivity (Table 1, entry 2). The use of 25 mol % of 3a was required to drive the reaction to completion with 86% yield (Table 1, entry 3). This result

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• ) and ≈2 ppm (13C NMR). To prevent acidic degradation, 6 was treated with palladium on charcoal under a hydrogen atmosphere (Table 1, entries 3–5). In MeOH as the solvent, transglycosylation of the seleno glycoside 6 to its methyl O-glycoside was observed (Table 1, entry 3). Changing the solvent to the

Natural phenolic metabolites with anti-angiogenic properties – a review from the chemical point of view

• Qiu Sun,
• Jörg Heilmann and
• Burkhard König

Beilstein J. Org. Chem. 2015, 11, 249–264, doi:10.3762/bjoc.11.28

• xanthohumol intake [77]. To date, xanthohumol in vivo metabolites have not been investigated regarding their anti-angiogenic activity. Genistein Genistein (60) is an isoflavone extracted from soybeans (Glycine max (L.) MERR, Fabaceae). It is present as the 7-O-glycoside genistein in the plant; however, during

Synthesis and structure of tricarbonyl(η⁶-arene)chromium complexes of phenyl and benzyl D-glycopyranosides

• Thomas Ziegler and
• Ulrich Heber

Beilstein J. Org. Chem. 2012, 8, 1059–1070, doi:10.3762/bjoc.8.118

• reacting acetobromoglucose with 6-tert-butyl-2-hydroxypyridine [20] under Helferich conditions (Hg(CN)2). Only the corresponding O-glycoside 1l was obtained, and no N-glycoside was formed in this Helferich glycosylation (Scheme 1). Sterically hindered 6-tert-butyl-2-hydroxypyridine was chosen as the