The role of sugar configuration in the acetolysis of 6-deoxyhexose methyl glycosides.
The acetolysis of several perbenzylated 6-deoxyhexose methyl glycosides under two mild conditions (10 equiv ZnCl(2) in 2:1 v/v Ac(2)O-AcOH at 5 degrees C; 10:10:1 v/v/v Ac(2)O-AcOH-TFA at 70 degrees C) was studied. We focused on the effect of sugar configuration on the competition between mechanisms with activation at exocyclic or endocyclic oxygen site. No effect was detected in acetolysis using the TFA protocol promoting an exo-activation mechanism, which affords 1-O-Ac-pyranosides regardless of sugar configuration. On the contrary, it has a primary role in determining the endo- versus exo-product distribution on ZnCl(2)-promoted acetolysis.
Dipartimento di Chimica Organica e Biochimica, Università di Napoli Federico II, Complesso Universitario Monte S.Angelo, Via Cintia 4, 80126 Napoli, Italy.
Luigi
L
Cirillo
Annalida
A
Di Nola
Emiliano
E
Bedini
Michelangelo
M
Parrilli
D000080:Acetals / Q000737:chemistry; D000107:Acetylation; D002236:Carbohydrate Conformation; D008759:Methylglycosides / Q000737:chemistry*
D000080:Acetals; D008759:Methylglycosides