149220-52-0Relevant articles and documents
NOVEL D-GLUCANS OBTAINED BY DIMETHYL SULFOXIDE EXTRACTION OF THE LICHENS Letharia vulpina, Actinogyra muehlenbergii, AND AN Usnea SP.
Iacomini, Marcello,Gorin, Philip A. J.,Baron, Madalena,Tulloch, Alexander P.,Mazurek, Mytosk
, p. 117 - 126 (1988)
Extraction of certain lichens with cold dimethyl sulfoxide provided a β-D-glucan virtually free of contaminating α-D-glucan and galactomannan.Applied to Letharia vulpina, the method gave β-D-glucan, and extraction of the residue with hot water followed by cooling gave α-D-glucan.From Usnea sp. a β-D-glucan was isolated, but little α-D-glucan was present.Extraction of Actinogyra muehlenbergii provided a (16)-linked β-D-glucopyranan containing one acetyl group of every 8-9 glucosyl units, being present almost exclusively as monosubstituent at O-2, O-3, and O-4.
An Approach to the Synthesis of Electron-Rich and Hindered Esters and Its Application to the Synthesis of Acteoside
Zhang, Xiaojuan,Yang, Yutong,Wang, Fuye,Zhou, Zhengbing,Zhang, Hongbin,Zhu, Yugen
supporting information, p. 9210 - 9215 (2021/11/30)
Electron-rich esters are ubiquitously distributed in natural products and play a central role in bioactivities. Herein, we disclose an efficient, mild, and general esterification approach to the synthesis of these esters by employing gold(I)-catalyzed acylation reaction with alkyne-tethered mixed anhydrides and alcohols. This method can be applied to ester-bond formation in complex substrates and facilitates efficient synthesis of acteoside, which belongs to the family of phenylethanoid glycosides and possesses a broad range of bioactivities.
Regioselective acetylation of diols and polyols by acetate catalysis: Mechanism and application
Ren, Bo,Rahm, Martin,Zhang, Xiaoling,Zhou, Yixuan,Dong, Hai
, p. 8134 - 8142 (2015/03/18)
We propose a principle for H-bonding activation in acylation of hydroxyl groups, where the acylation is activated by the formation of hydrogen bonds between hydroxyl groups and anions. With the guidance of this principle, we demonstrate a method for the selective acylation of carbohydrates. By this method, diols and polyols are regioselectively acetylated in high yields under mild conditions using catalytic amounts of acetate. In comparison to other methods involving reagents such as organotin, organoboron, organosilicon, organobase, and metal salts, this method is more environmentally friendly, convenient, and efficient and is also associated with higher regioselectivity. We have performed a thorough quantum chemical study to decipher the mechanism, which suggests that acetate first forms a dual H-bond complex with a diol, which enables subsequent monoacylation by acetic anhydride under mild conditions. The regioselectivity appears to originate from the inherent structure of the diols and polyols and their specific interactions with the coordinating acetate catalyst.