3-(3,4,5-trimethoxyphenyl)isoxazol-5-yl]resorcinol 3 was generated in
a Stille coupling between 4,6-diiodoresorcinol and 2 mol ributylstanny
l-3-(3,4,5-trimethoxyphenyl)isoxazole 2. 4-Iodoresorcinol was coupled
with 3-phenyl-5-tributylstannylisoxazole to give 5-(2,4-dihydroxypheny
l)-3-phenylisoxazole 7. Selective iodination of 7 with ICl gave 5-(2,4
-dihydroxy-5-iodophenyl)-3-phenyl-isoxazole 8, which underwent Stille
coupling with 2 to give 3-(3,4.5-trimethoxyphenyl)isoxazol-5-yl]resorc
inol 9. Reductive ring cleavage of 3 and 9 followed by acid-catalysed
cyclisation gave 5-trimethoxyphenyl)pyrano[3,2-g]chromene-4,6-dione 4
and 5-trimethoxyphenyl)pyrano[3,2-g]chromene-4,6-dione 10, respectivel
y, in fair overall yields.