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Geranylation of some synthetic and natural flavones have yielded cytotoxic products against L1210 coil; 5, 2´-dihydroxy-6, 7, 8-trimethoxy-6´-geranyloxyflavone 4(8.5μg/ml), 5, 6-dihydroxy-7-gerenyloxyflavone 9(2. 3pg/ml). 2 has showed the same range of cytotoxicity as the starting material, 5, 2´-dihydroxy--6, 7, 8-trimethoxy-6´-benzyloxyflavone(17. Opg/ml). The cytotoxicity of 4 was lower than its starting substance, 5, 2´, 6´-trihydroxy-6, 7, 8-trimethoxyflavone (4.5μg/nil). On geranylating 5, 6, 7-trihydroxyflavone(baicalein, 15.0μg/ml) the cytotoxic activity has been strongly potentiated(2. 3pg/ml of 9). The presence of at least a free hydroxy group in B-ring of Skullkapflavone II-type flavones. was essential for a high activity. A larger RD-group than methoxy in the B-ring has weakened the activity. The cytotoxicities of baicalein series could not be correlated to their structures.
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