Oh

MeOH, H20

Scheme 49

(170)

As for drugs for skin pathologies, it is known that the antipsoriatic dihydroxyanthrone dithranol (171) undergoes self-sensitised oxidation to the corresponding anthraquinone (172) and dianthrone (173) derivatives as well as polymerisation (Scheme 50).171 The action of psoralenes (e.g. methoxsalen, 174), used in phototherapy for controlling the skin disorder vitiligo, is based on their capacity of binding covalently with DNA through a photochemical reaction and/or of acting as photosensitisers and causing a specific damage to the cell via singlet oxygen. 172>173 Photostability is obviously important with these drugs which are used under irradiation. Their structure makes them liable to photodimerisation, however.

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