Novel dimeric derivatives of leucomycins and tylosin, sixteen-membered macrolides.

The reductive amination of an aldehyde group on the aglycon moiety of leucomycins A3 and A5 and tylosin with sodium cyanoborohydride in the presence of NH(CH3)2 or NH2CH3 afforded the corresponding amine derivative. The use of NH3 as an amine source in the reduction of leucomycin A3 and tylosin afforded a novel dimeric derivative, 18,18'-dideoxo-18,18'-iminodileucomycin A3 and 20,20'-dideoxo-20,20'-iminoditylosin, respectively. The structures of the dimers were elucidated by field desorption mass spectral analysis. The dimeric derivative of tylosin possesses considerable antibacterial activity. The binding activity of the dimer of Escherichia coli ribosome was approximately the same as for tylosin.