201211-99-6Relevant academic research and scientific papers
Highly diastereoselective α-mannopyranosylation in the absence of participating protecting groups
Crich, David,Cai, Weiling,Dai, Zongmin
, p. 1291 - 1297 (2007/10/03)
S-Phenyl 2,6-di-O-benzyl-3,4-O-(2',3'-dimethoxybutane-2',3'-diyl)- 1- thia-α-D-mannopyranoside and its sulfoxide, following activation at -78 °C with benzenesulfenyl triflate or trifiic anhydride, respectively, provide the corresponding α-mannosyl triflate as demonstrated by NMR spectroscopy. On addition of an acceptor alcohol α-mannosides are then formed. Similarly, S- phenyl 2,3-O-carbonyl-4,6-O-benzylidene-1-thia-α-D-mannopyranoside and ethyl 3-O-benzoyl-4,6-O-benzylidene-2-O-(tert-butyldimethylsilyl)-1-thia-α-D- mannopyranoside both provide α-mannosides on activation with benzenesulfenyl triflate followed by addition of an alcohol. These results stand in direct contrast to the highly β-selective couplings of comparable glycosylations with 2,3-di-O-benzyl-4,6-O-benzylidene protected mannosyl donors and draw attention to the subtle interplay of reactivity and structure in carbohydrate chemistry.
