Patent ID: 7208495

Claim:
A compound represented by the formula: (wherein, R 1 and R 2 are the same or different and each represents a hydrogen atom, optionally substituted hydrocarbon group or optionally substituted heterocyclic group, or R 1 and R 2 may form, together with the adjacent carbon atom, a 3–8 membered iso- or heterocyclic group which may optionally substituted, R 3 represents an optionally substituted cyclic group, X represents a bond or a spacer of 1–3 atoms, and R 4 represents a hydrogen atom, an optionally substituted hydrocarbon group, optionally substituted hydroxy group, optionally substituted mercapto group which may have oxo, or an optionally substituted amino group, or R 2 and R 4 may link together to form a double bond, W represents an oxygen atom or a sulfur atom, ring B represents an optionally substituted 4–8 membered nitrogen-containing heterocyclic group, and ring C represents a benzene ring which may also be optionally substituted in addition to the group represented by ring B but not via a nitrogen atom, and≡represents a single bond or a double bond), or a salt thereof.