When all the available evidence for the structure of bacitracin A is considered, the most probable one is that shown in Fig. l. 1-4 It would seem most likely that a linear dodecapeptide is first synthesized by the organism and that two rings are then formed as shown in Fig. 2. The thiazoline ring is now well e~ tablished,~~ but direct evidence for the linkage connecting the aspartyl-P-carboxyl group and the 6-amino-nitrogen of the lysine ...