The structure of a 2-deoxystreptamine (DOS) precursor named S-11-P, which was isolated by using a DOS negative mutant derived from a xylostasin-producing strain of Bacillus circulans B15M, has been elucidated as (1 L)-1,3,5/2,4,-5-aminocyclohexanetetrol by comparison with an authentic specimen, which was synthesized from kanamycin A.