Brønsted Acid-Promoted Glycosylations of Disaccharide Glycal Substructures of the Saccharomicins
摘要:
An acid-promoted glycosylation and alkynol cycloisomerization sequence provided direct access to the 2-deoxytrisaccharide corresponding to the fucose-saccharosamine-digitoxose substructure of saccharomicin B. In the course of this work, the absolute stereochemistry of the repeating fucose-saccharosamine disaccharide of saccharomicins was also confirmed.
Fischer Carbene Catalysis of Alkynol Cycloisomerization: Application to the Synthesis of the Altromycin B Disaccharide
作者:BonSuk Koo、Frank E. McDonald
DOI:10.1021/ol070435s
日期:2007.4.1
[reaction: see text] The tungsten-catalyzed cycloisomerization of alkynyl alcohols can be conducted without using photochemistry, using a stable tungsten Fischer carbene as the precatalyst for this transformation. A variety of alkynyl alcohols undergo cycloisomerization under these conditions to provide endocyclic enol ethers of five-, six-, and seven-membered ring sizes. The utility of this method is further