Stereoselective Synthesis of 2-deoxy Glycosides Via Anomeric O-alkylation

Download or read book Stereoselective Synthesis of 2-deoxy Glycosides Via Anomeric O-alkylation written by Danyang Zhu and published by . This book was released on 2015 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: 2-Deoxy sugars are an important class of carbohydrates which exist in a wide range of bioactive natural products and have been found to play vital role in biological activity of those natural molecules. Due to limited amounts of these molecules can be isolated from natural sources, it is critical to develop efficient tools for stereoselective synthesis of oligosaccharides in order to extensively study their structure and activity relationship for discovery of effective therapeutic agents. Despite a number of synthetic studies have been previously reported, stereoselective synthesis of 2-deoxy-glycosides still remains very challenging because of the lack of directing group at C-2 position. In this presentation, we have outlined an approach for direct synthesis of 2-deoxy-ß-oligosaccharides involving O-alkylation of anomeric alkoxides with challenging secondary triflates as electrophiles. We also found that a free hydroxyl group at C3 of the 2-deoxy-sugar-derived lactols is required to achieve synthetically efficient yields. Using this approach, 2-deoxy-ß-tetrasaccharide has been obtained in excellent yields. We also reported stereoselective synthesis of 2-deoxy a-digitoxosides and a-boivinosides via chelation-controlled anomeric O-alkylation using anomeric alkoxides containing C3 axial alkoxides and sugar-derived secondary triflates. In this chelation-controlled anomeric O-alkylation, the axial anomeric alkoxides are locked which lead to the formation of a-glycosides. Using this approach, a-digitoxosides and a-boivinosides have been successfully obtained.