A tripeptide on treatment with $\mathrm{PhNCS}(\mathrm{pH}=8.0)$ followed by heating with dilute HCl afforded a cyclic com pound M and a dipeptide. The dipeptide on treatment with $\mathrm{PhNCS}(\mathrm{pH}=8.0)$ followed by heating with dilute HCl afforded a cyclic compound N and an acyclic compound O . The CORRECT sequence (from N - to C terminus) of the tripeptide is M =N =O =