Anti:psoriasis agent 8-methoxy-psoralen prodn. - by multistage process from 6,7-di:hydroxy-coumaran-3-one

摘要

In the prodn. of 9-methoxy-7H-furo(3,2-g)(1)benzopyran-7-one (I), (a) 6,7-dihydroxycoumaran-3-one (II) is triacetylated with acetic anhydride, (b) the triacetylated cpd. (III) is catalytically reduced, (c) the reduction product (IV) is deacetylated under mild conditions to the hydroxy cpd. (V), (d) (V) is cyclised with acrylonitrile in the presence of ZnCl2 and HCl to give 2,3,5,6-tetrahydro-xanthotoxol (VI), (e) (VI) is methylated with dimethyl sulphate, and (f) the methylation product (VII) is dehydrogenated to (I) by heating with a dehydrogenation agent at 150 degrees C. (I) (8-Methoxypsoralen) is a known cpd. with a skin-photosensitising effect used in the treatment of psoriasis. Overall yield is 37.4%.