A novel heterocyclic compound or a salt thereof useful for selectively inhibiting the degradation of p27 kip1 is provided. The compound or the salt thereof is represented by the following formula (1): wherein A represents an alkyl group, a cycloalkyl group, an aryl group or a heterocyclic group, the group A may have a substituent； the ring B represents a 5- to 8-membered monocyclic heterocyclic ring or a condensed ring containing the monocyclic heterocyclic ring, the ring B may have a substituent； the ring C represents an aromatic ring, the ring C may have a substituent； L represents a linker comprising a main chain having 3 to 5 atoms selected from the group consisting of a carbon atom, a nitrogen atom, an oxygen atom and a sulfur atom, wherein at least one atom in the main chain is a hetero atom selected from the group consisting of a nitrogen atom, an oxygen atom and a sulfur atom, the linker L may have a substituent； and n is 0 or 1.
