Alguns derivados da β-Lapachona

Abstract

Lapachol, a- and b-lapachone are natural naphthoquinones found mainly in trees of the genus Tabebuia. The study of these substances has been stimulated mainly by the diversity of their biological activitys such as: trypanocidal, virucidal and inhibition oftopoisomerase enzymes, among others. In this work we studied the reactivity of the carbonyls of the quinone blapachone with various reagents in the formation of: dioxane rings, with stilbenes derivates through a photochemical process and, thermaly, with enamines; phenazines from 11,2- diamines; 1,3-dioxals from diazocompounds; and also reductive acylation with acetic anhydride and zinc. Trans-stilbene, 4,4'-dinitro- and 4,4'-dimethoxy-stilbene did not cyclize successfully by irradiation with b-lapachone, however, 2,3-di-phenyl-dioxene supplied a cycçization product (Schönberg adduct) with 86% yield. The compounds formed with enamines 1-piperidine- and 1-morpholine-cyclohexene were partially characterized, but were not stable. Among the diazocompounds tested diphenyl-diazo-methane was the only one to give a 1,3-dioxolone product. From ethylene-diamine and 5,6-diamino-uracil phenazines were prepared in reasonable yields. The structural elucidation of the products and intermediates was accomplished by IR, MS, NMR 1H and of 13C spectroscopies. The techniques of DEPT, homonuclear 1Hx1H and heteronuclear 1Hx13C correlation were used to aid the determination of some stmctures. Molecular modelling calculations (AM1) were perfomed to corroborate the obtained results and to suggest rational synthesis of new compounds from b-lapachone