cyclo(L-Ser-L-Val) is a diketopiperazine (DKP) prepared by the conjugation of L-serine and L-valine. cyclo(L-Ser-L-Val) is an intermediate in the synthesis of cylco(Δ-Ala-L-Val), an active quorum sensing metabolite produced by Pseudomonas aeruginosa and other Gram-negative bacteria. cyclo(L-Ser-L-Val) has not been reported as a natural product of bacteria or fungi and there is little research on its bioactivity.