Provided is a compound which is useful as a prophylactic or therapeutic agent for various diseases in which T-type calcium channels are involved, such as hypertension, arrhythmia, pain and cancers, the compound having antagonistic activity against T-type calcium channels, being highly stable in the body and having low risk of, for example, genotoxicity. Disclosed is a compound represented by the following general formula (I), a pharmaceutically acceptable salt thereof, or a solvate thereof: wherein R1 represents —NH(C═O)—V—R3 or —(C═O)NH—V—R3; V represents a single bond, methylene, or —C(CH3)2O—; R2 represents a optionally substituted C1-6 alkyl group; X represents a hydrogen atom, an oxygen atom, a hydroxyl group, a methyl group, or a methylene group; A represents —NR6—, —O—CH2—, or —S—CH2—; n represents the number of methylene chains and represents an integer of 0, 1 or 2; and a doublet containing a dotted line represents a single bond or a double bond.