Monosaccharides having a carbon–carbon double bond anywhere in the backbone chain. Glycals (term not recommended) designates the enoses that are generated by formal elimination of the hemiacetal hydroxy group and an adjacent hydrogen atom. Thus glycals are cyclic enol ethers. Unsaturated hexoses, for example, are called hexenoses, e.g. the hex-1-enopyranose derived from d-glucopyranose):