The synthesis of the core trisaccharide of esperamicin: corroboration of the proposed structure for its rearrangement product and stabilization of the core trisaccharide domain
concise, diversity‐oriented approach for the synthesis of naturally occurring 3‐amino‐ and 3‐nitro‐2,3,6‐trideoxypyranose derivatives and analogues thereof from simple sugars has been developed. In addition, we investigated the synthesis of various 3‐aminoglycosyl donors and their application in glycosylation reactions. These studies led to the successful synthesis of a tetrasaccharide containing four different
Allyl C-glycosidations of the totally unprotected glycals, L-rhamnal (1), D-glucal (2), D-galactal (3) and D-fucal (4), with allyltrimethylsilane (5) using TMSOTf proceeded much more effectively than those of the corresponding acetylated glycals 10∼13 to furnish the unprotected and 2,3-unsaturated allyl α-C-glycosides 6∼9 in high yields, respectively.
from -fucose is described. C3--virenose is the carbohydrate unit of the bioactive polyketide elsamicin B and part of the carbohydrate unit of elsamicin A. The developed route enabled preparation of anomerically activated forms of this unique C6-deoxy sugar, including derivatives with 1-acetyl, 1-acetylthio, 1-trichloroacetimidate, 1-bromo, and 1-fluoro substituents.
描述了从 β-岩藻糖合成受保护形式的病毒糖 C3-差向异构体的 9 步合成路线。 C3--virenose 是生物活性聚酮化合物 elsamicin B 的碳水化合物单元,也是 elsamicin A 碳水化合物单元的一部分。开发的路线能够制备这种独特的 C6-脱氧糖的异头活性形式,包括具有 1-乙酰基、1- 乙酰基的衍生物。乙酰硫基、1-三氯乙酰亚胺酯、1-溴和1-氟取代基。
Aryl and Allyl <i>C</i>-Glycosidation Methods Using Unprotected Sugars
Practical and highly stereoselective aryl and allyl C-glycosidation methods using unprotected sugars as glycosyl donors have been developed. Aryl C-glycosidations of several unprotected 2-deoxy sugars with phenol and naphthol derivatives by the combined use of trimethylsilyl trifluoromethanesulfonate (TMSOTf)-AgClO4 or TMSOTf exclusively gave the corresponding unprotected o-hydroxyaryl beta-C-glycosides which appear in many biologically attractive aryl C-glycoside antibiotics as the key subunit. On the other hand, allyl C-glycosidations of several unprotected glycals with allyltrimethylsilane by TMSOTf afforded the corresponding unprotected and 2,3-unsaturated allyl alpha-C-glycosides in high yields which are versatile synthetic intermediates for the syntheses of optically active natural products.