Protecting-group-free O-glysosidation using p-toluenesulfonohydrazide and glycosyl chloride donors.
A range of N'-glycosylsulfonohydrazides (GSHs) display good reactivity but poor stereoselectivity in protecting-group-free O-glycosidations when a moderate excess of the model acceptor n-decanol is employed. This stable, readily-accessed class of donor may be more tractable for the glycosylation of non-volatile acceptors than Fischer's glycosidation conditions. It is possible to generate unprotected glycosyl chlorides from GSHs in situ. In an effort to find conditions to improve glycosidation stereoselectivity, methanolysis of unprotected glucosyl chloride under halide-ion exchange conditions was examined. Relative to its tetra-O-benzyl analogue, this donor displays moderate, inverted stereoselectivity and a significantly faster reaction rate.
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Rohan J
RJ
Williams
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.
Caroline E
CE
Paul
Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada. Electronic address: mnitz@chem.utoronto.ca.
Mark
M
Nitz
D002712:Chlorides / Q000737:chemistry; D005947:Glucose / Q000031:analogs & derivatives* / Q000737:chemistry*; D006027:Glycosides / Q000138:chemical synthesis*; D006031:Glycosylation; D007474:Ion Exchange; D007700:Kinetics; D013237:Stereoisomerism; D014105:Tosyl Compounds / Q000737:chemistry*
D002712:Chlorides; D006027:Glycosides; D014105:Tosyl Compounds; D005947:Glucose; C002030:4-toluenesulfonyl hydrazide
Glycosyl chlorides; N′-Glycosylsulfonohydrazides; Protecting-group-free glycosidation; Protecting-group-free glycosylation