title: A study of n-pentenylorthoesters having manno, gluco and galacto configurations in regioselective glycosylations.
abstract: Kochetkov's extensive investigations of glycosyl orthoester and their analogs as glycosyl donors revealed that the alkyl derivatives were plagued by competition between the departing alcohol and the incoming acceptor. n-Pentenyl orthoesters (NPOEs) obviate competition by sequestering the departing pentenyl alcohol as a 2-halomethyl tetrahydrofuran. Exquisitely regioselective glycosidations of diol acceptors can be carried out with NPOEs triggered specifically with Yb(OTf)(3)/NIS. However with Sc(OTf)(3), double glycosidation is the major reaction. manno, gluco and galacto NPOEs have been investigated. The latter two, which require a different experimental procedure for the manno counterpart, also give an excellent regioselectivity with Yb(OTf)(3), but the yields are much lower than with manno.
authors.affiliation: Natural Products and Glycotechnology Research Institute, Inc., 595 F Weathersfield Road, Fearrington Post 595 F, Pittsboro, NC 27312, USA.
authors.forename: K N
authors.initials: KN
authors.lastname: Jayaprakash
authors.forename: Bert
authors.initials: B
authors.lastname: Fraser-Reid
mesh_terms: D002236:Carbohydrate Conformation; D004952:Esters / Q000737:chemistry*; D006027:Glycosides; D006031:Glycosylation; D013237:Stereoisomerism
chemical_list: D004952:Esters; D006027:Glycosides