Syntheses of antifungal isocoumarins. II. Synthesis and antifungal activity of 3-substituted isocoumarins.

Various 3-arylisocoumarins (5, 6, 8, 10, 11, and 12) were simply prepared in high yields by heating homophthalic acids (1-4) with aromatic acyl chlorides. 8-Hydroxy-3-phenylisocoumarin (17) and 8-acetoxy-3-phenylisocoumarin (18), and 8-hydroxy-3-(p-methoxyphenyl) isocoumarin (19) were obtained by alkaline hydrolysis of 10 and 11, respectively, followed by treatment with acetic anhydride. 3, 4-Dihydro-8-hydroxy-3-phenyl-isocoumarin (24) was prepared from 10 by alkaline hydrolysis followed by reduction with sodium borohydride then heating with acetic anhydride. 3-(p-Hydroxyphenyl)-isocoumarin (7), 8-hydroxy-3-(p-hydroxyphenyl) isocoumarin (9), 5-chloro-8-hydroxy-6-methoxy-3-phenylisocoumarin (13), and 3, 4-dihydro-3-(p-hydroxyphenyl) isocoumarin (23) were prepared by demethylation of 6, 8, 12 and 22, respectively. All the prepared isocoumarins and some other isocoumarin derivatives (25-30) were examined in vitro for antifungal activity. The structure-activity relationships are discussed.