The allyl ether as a protecting group in carbohydrate chemistry. Part IV. The 2-methylallyl ether group

Abstract

The O-2-methylallyl group, which is isomerised more slowly than the allyl group, is most suitable for use (in protection of OH) in the presence of the O-but-2-enyl group, since the latter can be eliminated without concomitant rearrangement of the 2-methylallyl group. 2-Methylallyl 2-benzamido-4,6-O-benzylidene-2-deoxy-β-D-gluco-and -galacto-pyranosides were prepared from the corresponding 3-O-but-2-enyl derivatives and these benzamido-derivatives were converted into the acetamido-derivatives by alkaline hydrolysis followed by acetylation. A convenient method for the conversion of an N-benzoyl amino-sugar into the corresponding N-acetyl amino-sugar by refluxing in acetic anhydride–glacial acetic acid is described. The benzylation of N-acetyl amino-sugars with benzyl chloride and sodium hydride is less satisfactory than the benzylation of the corresponding N-benzoyl amino-sugars, owing to extensive formation of N-benzylacetamido-derivatives.