Patent ID: 6933319

Claim:
A method of lightening skin or reducing the pigmentation of skin in a human, comprising administering to said human a skin-lightening or skin pigmentation-reducing effective amount of a compound of formula I: or a pharmaceutically acceptable salt thereof, wherein: R 1 is a (C 3 -C 8 )cycloalkyl ring or (C 5 -C 8 )cycloalkenyl ring, wherein either the cycloalkyl ring or cycloalkenyl ring is substituted by one to three substituents independently selected from the group consisting of cyano; halo; (C 1 -C 6 )alkyl; aryl; (C 2 -C 9 )heterocycloalkyl; (C 2 -C 9 )heteroaryl; aryl(C 1 -C 6 )alkyl-; ═O; ═CHO(C 1 -C 6 )alkyl; amino; hydroxy; (C 1 -C 6 )alkoxy; aryl(C 1 -C 6 )alkoxy-; (C 1 -C 6 )acyl; (C 1 -C 6 )alkylamino-; aryl(C 1 -C 6 )alkylamino-; amino(C 1 -C 6 )alkyl-; (C 1 -C 6 )alkoxy-CO—NH—; (C 1 -C 6 )alkylamino-CO—; (C 2 -C 6 )alkenyl; (C 2 -C 6 )alkynyl; hydroxy(C 1 -C 6 )alkyl-; (C 1 -C 6 )alkoxy(C 1 -C 6 )alkyl-; (C 1 -C 6 )acyloxy(C 1 -C 6 )alkyl-; nitro; cyano(C 1 -C 6 )alkyl-; halo(C 1 -C 6 )alkyl-; nitro(C 1 -C 6 )alkyl-; trifluoromethyl; trifluoromethyl(C 1 -C 6 )alkyl-; (C 1 -C 6 )acylamino-; (C 1 -C 6 )acylamino(C 1 -C 6 )alkyl-; (C 1 -C 6 )alkoxy(C 1 -C 6 )acylamino-; amino(C 1 -C 6 )acyl-; amino(C 1 -C 6 )acyl(C 1 -C 6 )alkyl-; (C 1 -C 6 )alkylamino(C 1 -C 6 )acyl-; ((C 1 -C 6 )alkyl) 2 amino(C 1 -C 6 )acyl-; —CO 2 R 2 ; —(C 1 -C 6 )alkyl-CO 2 R 2 ; —C(O)N(R 2 ) 2 ; —(C 1 -C 6 )alkyl-C(O)N(R 2 ) 2 ; R 2 ON═; R 2 ON═(C 1 -C 6 )alkyl-; R 2 ON═CR 2 (C 1 -C 6 )alkyl-; —NR 2 (OR 2 ); —(C 1 -C 6 )alkyl-NR 2 (OR 2 ); —C(O)(NR 2 OR 2 ); —(C 1 -C 6 )alkyl-C(O)(NR 2 OR 2 ); —S(O) m R 2 ; wherein each R 2 is independently selected from hydrogen, (C 1 -C 6 )alkyl, aryl, or aryl(C 1 -C 6 )alkyl-; R 3 C(O)O—, wherein R 3 is (C 1 -C 6 )alkyl, aryl, or aryl(C 1 -C 6 )alkyl-; R 3 C(O)O—(C 1 -C 6 )alkyl-; R 4 R 5 N—C(O)—O—; R 4 R 5 NS(O) 2 —; R 4 R 5 NS(O) 2 (C 1 -C 6 )alkyl-; R 4 S(O) 2 R 5 N—; R 4 S(O) 2 N(C 1 -C 6 )alkyl-; wherein m is 0, 1 or 2, and R 4 and R 5 are each independently selected from hydrogen or (C 1 -C 6 )alkyl; —C(═NR 6 )(N(R 4 ) 2 ); or —(C 1 -C 6 )alkyl-C(═NR 6 )(N(R 4 ) 2 ) wherein R 6 represents OR 2 or R 2 wherein R 2 is defined as above; with the proviso that the cycloalkenyl ring is not aromatic; with the proviso that when R 1 is a (C 5 -C 8 )cycloalkyl ring, or when R 1 is a (C 5 -C 8 )cycloalkenyl ring having the following structure: wherein n is 0, 1, 2 or 3, where such (C 5 -C 8 )cycloalkyl ring or (C 5 -C 8 )cycloalkenyl ring is substituted by hydroxy, (C 1 -C 6 )alkoxy-, aryl(C 1 -C 6 )alkoxy-, —OC(O)(C 1 -C 6 )alkyl, —OC(O)aryl(C 1 -C 6 )alkyl, —OC(O)phenyl, halo, (C 1 -C 6 )alkyl-, aryl(C 1 -C 6 )alkyl-, —SH, —S(C 1 -C 6 )alkyl, aryl(C 1 -C 6 )alkyl-S—, —NH 2 , —NH(C 1 -C 6 )alkyl, or aryl(C 1 -C 6 )alkyl-HN—; then the (C 5 -C 8 )cycloalkyl ring or the (C 5 -C 8 )cycloalkenyl ring must be di- or tri-substituted.