Compound 3 underwent 0-alkylation with allyl bromide and potassium carbonate in acetone to give the 3-(allyl-0xy) xanthone 4 as the major product and the l, &bis (al-1yloxy) xanthone 5 as the minor produce (12: l ratio). The 1-hydroxyl group of 3 is chelated (appearing at 6 12.81 in the NMR) with the carbonyl function and therefore is much less susceptible to 0- alkylation. The separation of 4 and 5 can be conveniently done by column ...