A novel heterocyclic compound or a salt thereofuseful for selectively inhibiting the degradation of p27Kip1is provided. The compound or the salt thereof is representedby the following formula (1) :(formula 1)wherein A represents an alkyl group, a cycloalkylgroup, an aryl group or a heterocyclic group, the groupA may have a substituent； the ring B represents a 5- to8-membered monocyclic heterocyclic ring or a condensed ringcontaining the monocyclic heterocyclic ring, the ring Bmay have a substituent； the ring C represents an aromaticring, the ring C may have a substituent； L represents alinker comprising a main chain having 3 to 5 atoms selectedfrom the group consisting of a carbon atom, a nitrogen atom,an oxygen atom and a sulfur atom, wherein at least one atomin the main chain is a hetero atom selected from the groupconsisting of a nitrogen atom, an oxygen atom and a sulfuratom, the linker L may have a substituent； and n is 0 or1.
