Assignments of labile protons (NH, OH-1, OH-4 and OH-8) and naphthalene carbon atoms in the 1H-and 13C-nuclear magnetic resonance spectra of rifampicin (1) and 3-[(dimethylhydrazono)-methyl]rifamycin SV (2) in CDC13 were made based on long-range selective decoupling experiments. The published assignments of the labile protons and two naphthalene carbon atoms (C-5 and C-9) of 1 should be revised.

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Rifamycin S (1) and 25-O-deacetylrifamycin S reacted with 1,3,5-tri-t-butylhexahydro-1,3,5-triazine to give deep-blue compounds. The structures of the deep-blue compounds are discussed based on 13C NMR data, and it is concluded that the earlier structures should be partly re-revised. The mechanism of formation of the deep-blue compounds and the reaction of 1 with several hexahydro-1,3,5-triazines, which were prepared from formaldehyde and primary aliphatic amines, are also described.

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