The structure of celesticetin is β-salicyloyloxyethyl 6,8-dideoxy-6-(1-methyl-L-pyrrolidine-2-carboxamido)-7-O-methyl-l-L-thio-D-erythro-D-gulo-octopyranoside. A partial structure of celesticetin (1) was incomplete as to questions regarding branching and stereoisomerism of the aminooctose as well as the relative locations of the methoxyl and amino groups on this sugar. Recent studies on lincomycin (2) produced by a different organism, S. lincolnensis, demonstrated its relationship to celesticetin. Subsequent investigations have disclosed a whole family of antibiotics in this class, produced by S. lincolnensis under various fermentation conditions. The lincomycin structure determination opened a new avenue into the complete elucidation of the celesticetin molecule. Results of this approach, in which an assumption of the identity of the lincomycin and celesticetin octosamines was verified, have appeared in a preliminary communication. Structures 3 and 4 were thus established for celesticetin and desalicetin, respectively.