Involved in the biosynthesis of pulcherrimin, a red extracellular pigment. It uses activated amino acids in the form of aminoacyl-tRNAs (aa-tRNAs) as substrates to catalyze the ATP-independent formation of cyclodipeptides which are intermediates in diketopiperazine (DKP) biosynthetic pathways. Catalyzes the formation of cyclo(L-Leu-L-Leu) (cLL) from L-leucyl-tRNA(Leu). Can also incorporate various nonpolar residues, such as L-phenylalanine, L-leucine and methionine, into cyclodipeptides. 2 L-leucyl-tRNA(Leu) = cyclo(L-leucyl-L-leucyl) + 2 H(+) + 2 tRNA(Leu) Monomer. Belongs to the CDPS family.