Synthesis of tetracycline analogs and their bone affinities

Tetracycline analogs were designed and synthesized and their bone affinities were tested on hydroxyapatite. The results showed that the carbonyl-amide-enol structure in A ring and phenol–ketone structure in BCD ring may be responsible for tetracycline's high bone affinity and either A ring or BCD ring has a planar conformation is essential.