A compound represented by the figure (1) or a pharmaceutically acceptable salt thereof is useful as medicament for treating retinal degenerative disorders:
wherein Ar is optionally substitued phenyl or optionally substituted heteroaryl;.
n is 0, 1 or 2;
W is —CH2NH— or —CH═N(O)—;
R1, R2 and R3 are independently optionally substituted alkyl, carboxyl or alkoxycarbonyl; any two groups of R1, R2 and R3 may be taken together with the carbon atom to form optionally substituted cycloalkane; all of R1, R2 and R3 may be taken together with the adjusent carbon atom to form optionally substituted bicycloalkane or optionally substituted tricycloalkane;
R4 and R5 are independently hydrogen atom or optionally substituted alkyl.