hours during which the temperature of the solution was gradually lowered to room temperature after removal of the solvent from the reaction mixture by distillation under reduced pressure 400 ml of pyridine and 100 ml of water were combined with the residue thus obtained thereafter the mixture was heated for 1 hour under refluxing and stirring conditions and its solvent fractions were removed by distillation under reduced pressure the resulting residue was allowed to stand overnight followed by addition of 800 ml of water the separated deposit was collected by filtration and air dried the deoposit was crystallized from ethanol to obtain 85 5 g yield 61 2 of 7 bromo 1 2 3 4 tetrahydro 9 xanthone as white needle like crystals having a melting point of 149 u00b0 c 150 5 u00b0 c nmr cdcl 3 u03b4 8 33 1h d j 3 hz ar h 7 85 7 20 2h m ar h 2 92 2 48 4h m ch 2 at the c 1 and c 2 positions 2 25 1 65 4h m ch 2 at the c 3 and c 4 positions ______________________________________ c h brcalculated 55 93 3 97 28 63found 56 03 4 11 28 61______________________________________ using the same operation as in example 1 the tetrahydroxanthone derivatives shown in table 1 were obtained table 1__________________________________________________________________________ melting appearance elementary analysis values point recrystalization yield molecular calculated found examplecompound u00b0 c solvent formula c h c h__________________________________________________________________________2 7 bromo 2 methyl 1 2 3 4 190 191 white needle like 52 7 c sub 14 h sub 13 bro sub 2 57 36 4 47 57.