Skin lightening compositions

A method of lightening or depigmenting the skin, comprising topically applying to skin in need of such treatment a topically applicable composition for lightening or depigmenting skin, comprising a safe and effective skin-lightening or depigmenting amount of at least one compound represented by the structural formula:

• wherein:
• R1 and R2 are same or different and are each selected from the group consisting of hydrogen, alkyl, carbomethoxy, carboethoxy, alkoxy, and alkanoyl, any of which may be halogen-substituted, and halogen;
• R6 is selected from the group consisting of hydrogen, methyl, and ethyl;
• and
• R3, R4 and R5 are the same or different and are each selected from the group consisting of hydrogen, methyl, methoxy, ethoxy, methoxyethoxy, ethoxyethoxy, propoxy, propoxymethoxy, and the like, any of which may be halogen-substituted;
• or a derivative or physiologically acceptable salt, solvate or bioprecursor, or stereoisomer or enantiomer thereof;
• or by the structural formula:
• wherein:
• R2 is hydrogen, lower alkyl or hydroxy lower alkyl;
• R3 is lower alkyl, —CH2CN, hydroxy lower alkyl, —NO, —CH2N═C or
• (wherein R6 and R7 are independently selected from the group consisting of hydrogen and lower alkyl) or hydrogen provided R2 is not hydrogen;
• R4 is Z-T-W wherein Z represents —O—, —NH— or a single bond;
• T represents a straight- or branched-chain lower-alkylene group;
• when Z is a single bond, T also represents an ethenylene or a propenylene group wherein the unsaturated carbon is at the single bond;
• when Z is —O—, T also represents an allylene group wherein the saturated carbon is at the oxygen;
• and W represents hydrogen, when T is allylene and Z is —O—, and Ar, wherein Ar is selected from thienyl, pyridinyl, furanyl, phenyl and substituted phenyl wherein there are one or more substituents on the phenyl independently selected from halogen or lower alkyl;
• and
• R5 is hydrogen, halogen or lower alkyl;
• or a derivative or physiologically acceptable salt, solvate or bioprecursor, or stereoisomer or enantiomer thereof;
• formulated into a topically applicable, cosmetically or dermatologically acceptable vehicle, carrier or diluent therefor.