The chemical synthesis of cecropin D and an analog with enhanced antibacterial activity.

Cecropin D was synthesized by solid-phase methods and shown to be homogeneous and of correct composition and molecular weight. It was indistinguishable from natural cecropin D and constitutes a structure proof for this peptide. Several analogs of cecropin D were synthesized and used to draw conclusions about the structural features contributing to antibacterial activity. They included [Lys1]cecropin D, [Gln3, Leu4] cecropin D, and cecropin D-(9-37). It was concluded that a strongly basic NH2-terminal segment is a prerequisite for antibacterial activity. A hybrid analog cecropin A-(1-11) D-(12-37) was designed and predicted to have enhanced potency. It was found to be 5 to 55 times as active as cecropin D against six of the bacteria tested and was slightly more active than cecropin A. However, against Bacillus subtilis Bs11 the analog was 6 times more active than cecropin A.