The novel inosose derivatives ##STR1## wherein Y.sup.1 stands for hydroxyl group and Y.sup.2 stands for hydrogen atom, or Y.sup.1 and Y.sup.2 are joined to form a bond between carbon and carbon atoms, and R.sup.1 and is a protective group for hydroxyl group, are useful as a starting material for producing valienamine, valiolamine and their N-substituted derivatives.