The alkaline isomerisation of allyl ethers of carbohydrates to the corresponding prop-1-enyl ethers and removal of the latter by dilute-acid hydrolysis has been used in the preparation of the following benzyl ethers: 2,3,4,6-tetra-O-benzyl-D-glucopyranose, 2,3,4,6-tetra-O-benzyl-D-galactopyranose, 3,4,6-tri-O-benzyl-D-galacititol, 5-O-benzyl-1,2-O-isopropylidene-D-glucofuranose, and 5,6-di-O-benzyl-1,2,-O-isopropylidene-D-glucofuranose. The prop-1-enyl group in 1,2:5,6-di-O-isopropylidene-3-O-prop-1′-enyl-D-glucofuranose could be removed by ozonolysis followed by alkaline hydrolysis or by the action of alkaline potassium permanganate solution.