Five-membered cyclic compounds

A compound of the formula:

• wherein X is a sulfur atom,
• R1 is a hydrogen atom, a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl,
• R2 is a hydrogen atom, a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl,
• Y1 is a direct bond, a substituted or unsubstituted alkylene, —CO(CH2)n—, —SO2(CH2)n—, —CONH(CH2)n—, —CSNH(CH2)n—, or —COO(CH2)n—,
• n is an integer of from 0 to 5,
• the wavy line means (E)-configuration or (Z)-configuration,
• R3 is a substituted or unsubstituted pyridyl,
• Y2 is a substituted or unsubstituted alkylene, or an alkenylene,
• R4 is a hydrogen atom, a substituted or unsubstituted alkanoyl, a substituted or unsubstituted alkyl, —COOR8, —SO2R9, —COR10, —CON(R11)R12, —CSN(R13)R14, a cycloalkyl, a substituted or unsubstituted aryl, or —C(═NH)N(R15)R16,
• R5 is a hydrogen atom, or a substituted or unsubstituted alkyl,
• R8 is a substituted or unsubstituted alkyl, a cycloalkyl, or a substituted or unsubstituted aryl,
• R9 is a substituted or unsubstituted alkyl, or a substituted or unsubstituted aryl,
• R10 is a cycloalkyl, or a substituted or unsubstituted aryl,
• R11 is a hydrogen atom or an alkyl,
• R12 is a hydrogen atom, a substituted or unsubstituted alkyl, a cycloalkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted arylcarbonyl,
• R13 is a hydrogen atom or an alkyl,
• R14 is a hydrogen atom, a substituted or unsubstituted alkyl, a cycloalkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted arylcarbonyl,
• R15 is a hydrogen atom or an alkyl,
• R16 is a hydrogen atom or a substituted or unsubstituted alkyl, or a pharmaceutically acceptable salt thereof, or a prodrug thereof.