The present invention provides, for example, the following compound: wherein ring Z is pyridine or a carbocycle, each of which is substituted or unsubstituted, ring A is a carbocycle or a heterocycle, each of which is substituted or unsubstituted, R 1 is substituted or unsubstituted alkyl or the like, R 2a , R 2b , R 4a and R 4b are each independently hydrogen or substituted or unsubstituted alkyl or the like, its pharmaceutically acceptable salt or a solvate thereof having an effect of inhibiting amyloid 6 production, especially a BACE1 inhibitory activity, and useful as a medicament for treating diseases induced by production, secretion or deposition of amyloid ß proteins.
