Is donor-acceptor hydrogen bonding necessary for 4,6-O-benzylidene-directed beta-mannopyranosylation? Stereoselective synthesis of beta-C-mannopyranosides and alpha-C-glucopyranosides.
2,3-Di-O-benzyl-4,6-O-benzylidene-thiohexopyranosides, on activation with 1-benzenesulfinyl piperidine and triflic anhydride, react with allyl silanes and stannanes, and with silyl enolethers to give C-glycosides. In the mannose series the beta-isomers are formed selectively whereas the glucose series provides the alpha-anomers. This selectivity pattern parallels that of O-glycoside formation and eliminates the need to consider donor-acceptor hydrogen bonding in the formation of the O-glycosides.
Crich
David
D
Department of Chemistry, Wayne State University, 5101 Cass Avenue, Detroit, Michigan 48202, USA. dcrich@chem.wayne.edu
Sharma
Indrajeet
I
D001597:Benzylidene Compounds / Q000737:chemistry*; D005947:Glucose / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D006860:Hydrogen Bonding; D008358:Mannose / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry
D001597:Benzylidene Compounds; D013438:Sulfhydryl Compounds; D005947:Glucose; D008358:Mannose