SYNTHESIS OF ANTHRACYCLINONES VIA ORTHO-QUINONOID PYRONES

Dehydration of the acid 3 (R = H) with acetic anhydride at 80-degrees-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.