The reaction of 3-benzyloxy-4-hydroxy-2-methoxyxanthone with ethyl-2-bromo-3-(4-benzyloxy-3-methoxyphenyl)-3-oxopropionate in the presence of potassium tert-butoxide afforded the condensation product (8) which was converted to the debenzylation product (9) by hydrogenolysis. Reduction of 9 with lithium borohydride followed by treatment of resulting alcohols (10a, b) with concentrated hydrochloric acid in acetic acid provided kielcorin.