Cyclo(-Ala-Gln) is a cyclic dipeptide composed of L-alanine and L-glutamine. It is a diketopiperazine (DKP) derivative, characterized by a stable 2,5-diketopiperazine ring structure formed by the cyclization of the two amino acids. This structural motif often confers enhanced metabolic stability compared to linear peptides. This compound is primarily investigated in the field of pharmaceutical sciences. Its core application lies as a prodrug or a stable alternative to L-alanyl-L-glutamine (Ala-Gln), a dipeptide used in parenteral nutrition to provide glutamine, a conditionally essential amino acid crucial for immune function and gut integrity. The cyclic form may offer improved solubility and stability profiles. Research also explores its potential as a functional excipient or a bioactive scaffold in drug delivery systems due to its peptidomimetic nature. As a specialized cyclic dipeptide, it is not a common, general-purpose synthetic building block. Its development and use are closely tied to specific biomedical applications, particularly in enhancing nutrient formulations and exploring novel therapeutic or delivery platforms.