Synthesis and cytotoxic activity of benzopyranoxanthone analogues of benzo[b]acronycine and psorospermine

Condensation of 3-hydroxy-2-naphthalenecarboxylic acid with phloroglucinol afforded 1,3-dihydroxy-12H-benzo[b]xanthen-12-one. Construction of an addit ional dimethylpyran ring onto this skeleton, by alkylation with 3-chloro-3- methyl-1-butyne followed by Claisen rearrangement, gave access to a series of benzo[b]pyrano[2,3-i]xanthen-6-ones and benzo[b]pyrano[3,2-h]xanthen-7-o nes related to psorospermine and benzo Ib] acronycine, In contrast with wha t is observed in the pyridoacridone and benzopyridoacridone series, the lin ear benzo[b]-pyrano[2,3-i]xanthen-6-one derivatives were more potent than t heir angular benzo[b]pyrano[3,2-h]xanthen-7-one isomers, cis-3,4-Diacetoxy- 5-methoxy-2,2-dimethyl-3,4-dihydro-2H,6H-benzo[b]pyrano[2,3-i]xanthen-6-one the most active among the new compounds, was more potent than acronycine i n inhibiting the proliferation of L1210 murine leukemia cells.