I was working on a synthetic problem involving the abiotic synthesis of amino acids (not a homework question). It has been proposed that, in early earth conditions, DAMN (diaminomaleonitrile) catalyzes the formation of dipeptides -- in this case gly-gly. However, it has been found that only a minimal amount of the dipeptide (or, for that matter, tripeptide, etc) is formed... What happens is, after gly-gly forms, the amino group of the gly not attached to DAMN comes in and attacks the carbonyl group of the activated ester and forms cyclic diglycine (diketopiperazine), the major reaction product. My question is, [STRIKE]how do you predict when a cyclization occurs as in this case.[/STRIKE] In amino acid polymerization reactions outside of the body, is cyclization something you always want to check for?