Synthesis of alpha- and beta-glycosyl isothiocyanates via oxazoline intermediates.
A practical synthesis of acylated glycosyl isothiocyanates from sugar oxazolines, by reaction with thiophosgene, is reported. In the absence of any additive, the reaction is governed by the reverse anomeric effect, leading to the equatorially oriented isothiocyanate. However, in the presence of copper(II) chloride, the reaction proceeds preferentially with retention of the configuration at the anomeric center, providing the axial anomer as the major product. Noteworthy, this strategy allows accessing per-O-acetylated glycopyranosyl isothiocyanates with 1,2-cis relative configuration (e.g., the alpha-anomer in the D-gluco and D-galacto series), a problem that was outside the scope of previous methodologies.
Blanco
José L Jiménez
JL
Departamento de Química OrgAnica, Facultad de Química, Universidad de Sevilla, Apartado 553, E-41071 Sevilla, Spain.
Sylla
Balla
B
Mellet
Carmen Ortiz
CO
Fernández
José M García
JM
D002236:Carbohydrate Conformation; D006027:Glycosides / Q000138:chemical synthesis*; D017879:Isothiocyanates / Q000138:chemical synthesis*; D010080:Oxazoles / Q000737:chemistry*
D006027:Glycosides; D017879:Isothiocyanates; D010080:Oxazoles; C064210:oxazolidine