Novel cyclic tetrapeptide derivatives and pharmaceutical use thereof

Abstract From the Canadian patent

Cyclic tetrapeptide derivatives represented by general formula (I) or pharmaceutically acceptable salts thereof: (wherein R21 and R22 are each independently hydrogen, linear C1-C6 alkyl to which a nonaromatic cycloalkyl group or an optionally substituted aromatic ring may be bonded or branched C3-, C6 alkyl to which a nonaromatic cycloalkyl group or an optionally substituted aromatic ring may be bonded; and R1 and R3 are each independently linear C1-C5 alkylene which may have a C1-C6 side chain and the side chain may form a , fused ring structure on the alkylene chain). Histone deacetylase inhibitors MHC class I molecule development promotors and drug compositions containing , as the …