An unusual course of thioglycoside activation with bromine: synthesis and crystal structure of 4-O-acetyl-2-bromo-2,3,6-trideoxy-3-C-methyl-3-trifluroacetamido-alpha-L-altropyranosyl bromide.
Bromine activation of phenyl 4-O-acetyl-2,3,6-trideoxy-3-C-methyl-3-trifluoroacetamido-1-thio-alpha,beta-L-ribo-hexopyranoside and attempted coupling with an acceptor in the presence of silver silicate gave an unusual bicyclic product, 2-trifluoromethyl-(4-O-acetyl-2-bromo-2,3,6-trideoxy-3-C-methyl-alpha-L-altrohexopyrano)-[3,2,1-d,e]-2-oxazine, instead of the expected disaccharide. Detailed investigation supported by X-ray crystallographic analysis showed that a trans dibromide is an intermediate in this reaction and that the dibromide is likely formed from a glycal that is generated by elimination during the coupling step.
Dulin
Mildred L
ML
Department of Chemistry, Villanova University, PA 19085, USA.
Noecker
Lincoln A
LA
Kassel
W Scott
WS
Giuliano
Robert M
RM
D001966:Bromine / Q000737:chemistry*; D003460:Crystallization; D006027:Glycosides / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013865:Thioglycosides / Q000138:chemical synthesis* / Q000737:chemistry; D014961:X-Ray Diffraction / Q000379:methods
C481485:4-O-acetyl-2-bromo-2,3,6-trideoxy-3-C-methyl-3-trifluroacetamido-alpha-L-altropyranosyl bromide; D006027:Glycosides; D013865:Thioglycosides; D001966:Bromine