ABSTRACT
We report the first total synthesis of scleropentaside D, a unique C-glycosidic ellagitannin, from the ketal derivative of scleropentaside A employing site-selective O4-protection of C-acyl glycoside and copper-catalyzed oxidative coupling reaction of galloyl groups as the key steps. Our study confirms the proposed structure of this natural product, scleropentaside D, and demonstrates its effectiveness as an inhibitor of α-glycosidase.
Subject(s)
Hydrolyzable Tannins , Hydrolyzable Tannins/chemistry , Hydrolyzable Tannins/pharmacology , Hydrolyzable Tannins/chemical synthesis , Molecular Structure , Glycosides/chemistry , Glycosides/chemical synthesis , Glycosides/pharmacology , Glycoside Hydrolases/antagonists & inhibitors , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Enzyme Inhibitors/chemistry , CatalysisABSTRACT
C-Glycosylation involving glycosyl radical intermediates is a particularly effective approach to access C-glycosides, which are core units of a great number of natural products, bioactive compounds and marketed drugs. In this review, we summarize the progress of glycosyl radical-based C-glycoside synthesis between 1999-2020, focusing on the stereoselectivity and recently developed methodologies such as α-alkoxyacyl telluride-related, photo-mediated and transition-metal catalysed reactions. Metal-mediated reductive cross coupling is also covered due to its close relationship with the latter approaches. To introduce several strategies for achieving uncommon ß-stereoselective C-glycosylation, we also briefly described organotin-based methods.
Subject(s)
Glucose/chemistry , Glycosides/chemical synthesis , Carbohydrate Conformation , Carboxylic Acids/chemistry , Catalysis , Glycosylation , Oxidation-Reduction , Photochemical Processes , Stereoisomerism , Transition Elements/chemistry , Uronic Acids/chemistryABSTRACT
With glycosyl ortho-alkynylbenzoates as donors, the highly efficient glycosylation of flavonoid 5-OH which are notorious for their low reactivity due to their involvement in the formation of strong intramolecular H-bonds was achieved under the catalysis of a Au(i) complex. Thus, a series of flavonoid 5-O-glycosides, including a kaempferol 5-O-disaccharide, were synthesized with good to excellent yields.
