Disclosed is a compound represented by General formula (I), a pharmaceutically acceptable salt thereof, or a solvate of the compound or the pharmaceutically acceptable salt, which has an inhibitory activity of the production of Aβ or a BACE1-inhibiting activity, and is therefore useful as a prophylactic or therapeutic agent for Aβ-induced neurodegenerative diseases typified by Alzheimer-type dementia. Wherein the ring A represents a C
