Acridone alkaloids pyrano-acridones

In regard to the antineoplastic properties of Rutaceae, this family has attracted a great deal of interest for its ability to elaborate series of cytotoxic benzo[c]phenanthri-dine and acridin alkaloids. Examples of acridin alkaloid are pyrano-acridone and acronycine characterized from Acronychia baueri Scott. 

As part of a general study of the synthesis of 2,2-dimethylpyrano-derivatives, a convenient synthesis of the acridone alkaloid, acronycine (31 R = R = Me) was devised. Heating a solution of 1,3-dihydroxyacridone and 4,4-dimethoxy-2-methylbutan-2-ol in pyridine afforded a mixture of linear and angular pyrano derivatives. The angular product (31 R = R = H), which predominated, is itself a natural compound and was converted by methylation into acronycine. 

---