2-(Trimethylsilyl)ethyl Glycosides. Synthesis, Anomeric Deblocking, and Transformation into 1,2-Trans 1-O-Acyl Sugars

Article abstract of DOI:10.1021/jo00259a006

Twenty-seven mono --> tetrasaccharidic 2-(trimethylsilyl)ethyl (TMSET) glycosides were synthesized by the Koenigs-Knorr-type method in combination with a wide range of standard reagents for glycoside synthesis and protecting-group chemistry.Variously protected TMSET glycosides were treated with BF3*Et2O (0.7-0.8 equiv) and different carboxylic anhydrides (1.1-15 equiv) in toluene at 22-55 deg C, which gave in one step the corresponding protected 1-O-acyl sugars.In the majority of cases, the yields of purified compounds exceeded 90percent and the anomeric configuration of the starting TMSET glyoside was conserved to a large extent (>95percent) in most of the 1-O-acylated products.Unprotected and acetyl-, benzoyl-, benzyl-, dimethyl-tert-butylsilyl-, and phthaloyl-protected mono-->tetrasaccharidic TMSET glycosides were anomerically deblocked by using trifluoroacetic acid in dichloromethane at 0-22 deg C for 10-30 min.The hemiacetal products were isolated in 88-96percent yield; all reagents and byproducts were volatile and easily removed.