The first total synthesis of a (potential) dimeric carbazole alkaloid is described.After an improved preparation of the monomeric building block, 'biomimetic dimerization' by oxidative phenolic coupling was best achieved with di-fed-butyl peroxide in chlorobenzene, leading to a highly selective formation of the 2,2'-coupled 'dimer', the parent framework of several naturally occurring dimeric carbazole alkaloids.For the atropoenantiomer analysis, a chromatographic procedure on a chiral phase was developed.Both the mono-and the dimeric phenolic carbazoles displayed in vitro antimalarial activity against Plasmodium falciparum.The genus Murraya (Rutaceae) consists of nine tropical plant species,"s3 many of which are used in folk medicine.Thus, M. euchrestifolia, which is endemic to Taiwan, is used as an analgetic for local anaesthesia, as well as for the treatment of eczema, rheumatism and d r ~p s y .~ A phytochemical investigation of this species revealed the presence of a series of carbazole alkaloids, among them murrayafolines A (la) and B (2).5Moreover, related alkaloids like murrayaquinone A (3) and bismurrayafoline B (4), apparently arising from phenolic precursors l b and 2, by oxidative oxygenation resp.'dimerization', were isolated from the same ~l a n t .~, ~ Due to restricted rotation around the central biaryl axis, 4 should display the phenomenon of atropoisomerism.Regrettably, no attention has been paid to this stereochemical aspect during the structure elucidation work, so that an optical rotation for this natural biaryl was not measured.6Nothing is known about the biological activity of such biscarb-
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Bringmann et al. (1995) studied this question.