Tricyclic compounds

A compound represented by the following general formula (XXI), or a salt thereof:

• wherein:
• A″ represents a ring of the following formula:
• where said ring may have one or more substituents selected from lower alkyl groups, lower alkoxy groups and halogen atoms, and where the lower alkyl and lower alkoxy groups may have one or more substituents;
• R101 represents a lower alkyl group or a lower acyl group, which groups may contain a ring structure, and may have one or more substituents;
• R102 represents a hydrogen atom or an alkyl group having a total of 1 to 20 carbon atoms, which alkyl group may contain a ring structure, and may have one or more substituents;
• R103 represents an alkyl group having a total of 1 to 20 carbon atoms, which alkyl group may contain a ring structure, and may have one or more substituents;
• and
• R102 and R103, together with the nitrogen atom to which they are bonded, may form a ring, which ring may contain one or more hetero atoms as ring members in addition to the nitrogen atom to which R102 and R103 are bonded, and which ring may have one or more substituents;
• and
• R104, R105 and R106 each independently represent a substituent selected from a hydrogen atom, a hydroxyl group, a lower alkyl group, a lower acyl group, a lower alkoxy group, a halogen atom, an amino group, a mono(lower alkyl)amino group, a di(lower alkyl)amino group, a lower acylamino group and an amido group, which substituent may have one or more substituents.