The following diketopiperazines have been identified in roasted cocoa: Cyclo(-Pro-Leu-), Cyclo(-Val-Phe-), Cyclo(-Pro-Phe-), Cyclo(-Pro-Gly-), Cyclo(-Ala-Val-), Cyclo(-Ala-Gly-), Cyclo(-Ala-Phe-), Cyclo(-Phe-Gly-), Cyclo(-Pro-Asn-), Cyclo(-Asn-Phe-). The typical bitterness of cocoa is due to an interaction of the purine theobromine ( 2) and diketopiperazines, which are formed during the roasting of the coca beans.