Total synthesis of everninomicin 13,384-1 - Part 4: Explorations of methodology; Stereocontrolled synthesis of 1,1 '-disaccharides, 1,2-seleno migrations in carbohydrates, and solution- and solid-phase synthesis of 2-deoxy glycosides and orthoesters

Methods for the stereocontrolled construction of 1,1'-disaccharides. 2-deox y glycosides, and orthoesters are reported. Specifically, a tin-acetal moie ty was utilized to fix the anomeric stereochemistry of a carbohydrate accep tor leading to an efficient and stereoselective synthesis of 1,1'-disacchar ides, while a newly discovered 1,2-phenylseleno migration reaction in carbo hydrates opened entries to 2-deoxy glycosides and orthoesters. Thus, reacti on of 2-hydroxy phenylselenoglycosides with DAST led to 2-phenylselenoglyco syl fluorides which reacted with carbohydrate accepters to afford, stereose lectively, 2-phenylselenoglycosides. The latter compounds could be reductiv ely deselenated to 2-deoxy glycosides or oxidatively converted to orthoeste rs via the corresponding ketene acetals.