The reaction of daunomycinone (IX) with AlCl3 in dichloromethane gives 4-demethyldaunomycinone (X), which is ketalized with ethylene glycol as before yielding the dioxolane (XI). The selective sulfonation of (XI) with TsCl, DIEA and DMAP in pyridine affords the 4-tosyloxy derivative (XII), which is treated with 4-methoxybenzylamine (XIII) in pyridine providing the secondary benzylamine (XIV). Elimination of the benzyl protecting group of (XIV) with TFA gives 4-amino-4-demethoxydaunomycinone ethylene ketal (XV), which is deaminated by reaction with TFA, NaNO2 and H3PO2 to give 4-demethoxydaunomycinone (XVI). Finally, this compound is submitted to fermentation with Streptomyces peucetius corneus, S. Peucetius caesius, S. Caeruleus, S. Peucetius, S. Coeruleorubidus, and other chemical or radio-induced mutants thereof.
The condensation of chiral tetraline (I) with phthalic anhydride (II) by means of AlCl3 at 180 C gives the naphthacenedione (III), which is ketalized at the acetyl group with ethylene glycol and p-toluenesulfonic acid yielding the dioxolane (IV). The hydroxylation of (IV) with Br2 and AIBN in CCl4/CHCl3 affords the 4-demethoxy-7-epidaunomycinone (V), which is isomerized with TFA yielding 4-demethoxydaunomycinone (VI) . The condensation of (VI) with the acylated hexopyranosyl chloride (VII) by means of CF3SO3Ag of Br2Hg affords the trifluoroacetylated 4-demethoxydaunomycin (VIII), which is finally treated with NaOH in order to eliminate the trifluoroacetyl groups