Furanose was found by the spectral methods to be preponderant in the equilibrated solutions of coriose and sedoheptulose, while pyranose was shown to be the main constituent in equilibrated DL-gluco-3-heptulose and D-ido-3-heptulose. These examples show stableness of five-membered ring having three hydroxyl groups vic and cis to each other, relative to six-membered ring having 1, 3-diaxial hydroxyl groups.
