ANTHRACYCLINES. CYCLOADDITIONS OF 9-CHLORO-10-HYDROXY-1,4-ANTHRAQUINONE WITH VARIOUS BUTA-1,3-DIENES

Article abstract of DOI:10.1246/cl.1982.1057

The Diels-Alder type cycloaddition of several substituted buta-1,3-dienes with 9-chloro-10-hydroxy-1,4-anthraquinone (10) affords an efficient, regiospecific access in two steps to tetracyclic ketones (12-14) which have been investigated as intermediates for the synthesis of anthracycline derivatives.Butadienes with a less asymmetric ?-electron distribution than 9 give lower regiospecificity in cycloadditions with 10.Depending on the substituents in the used butadiene, the obtained cycloadducts are transformed under the reaction circumstances into the aromatized products (15-20).