Synthesis of anthracyclinones via o-quinonoid pyrones

Abstract

Dehydration of the acid 3(R = H) with acetic anhydride at 80 °C generates the o-quinonoid pyrone 4 which can be trapped with several alkenes; the adduct 6(R = Me, P = SiEt₃) and its 9-epimer from 2-triethylsilyloxypropene are readily transformed into (±)-auramycinone whilst those [(6; R = vinyl, P = SiEt₃) and its 9-epimer] from 2-triethylsilyloxybuta-1,3-diene are readily converted into the methyl ethers 12, 13, 14 and 15 of which 12, 14 and 15 are known to be readily converted into (±)-aklavinone.