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Paper | Regular issue | Vol 63, No. 6, 2004, pp.1299-1310
Published online, 9th April, 2004
DOI: 10.3987/COM-04-10036
Functionalization of the Ring A in Some Benzo[g]pyridazino[1,2-b]phthalazine-6,13-dione Derivatives Related to Anthracyclinones

Rafael Jiménez, Ana M. Sanz, Fernando Gómez-Contreras,* M. Carmen Cano, María J. R. Yunta, Mercedes Pardo, and Lucrecia Campayo

*Departamento de Química Orgánica, Facultad de Ciencias Química, Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain

Abstract

A synthesis of benzo[g]pyridazino[1,2-b]phthalazine-6,13-dione derivatives (2) and (3), respectively related to the feudomicinone B and daunomicinone skeletons, has been accomplished by [4+2] cycloaddition of benzo[g]phthalazine-1,4-dione with the adequate 1,3-diene. Functionalization of ring A with hydroxy substituents has been performed by reaction with N-bromosuccinimide in acid aqueous medium, sodium hydroxide, or hydrobromic acid via the corresponding epoxide, and the stereochemical features of electrophilic additions involved are commented in terms of steric and stereoelectronic factors. Easy isomerization of the C2-C3 double bond allows the introduction of hydroxy groups at the C1 or C4 positions, paving a way to further formation of the glycosides derivatives related to natural anthracyclines.