The first total synthesis of the Murraya alkaloid murrastifoline-F (3), an unsymmetric, N,C-bonded heterobiarylic biscarbazole, is described. Starting from the likewise naturally occurringbut here synthetically prepared“monomer” murrayafoline-A (6), lead tetraacetate-mediated oxidative non-phenolic biaryl coupling gives 3 as the main regioisomer. The existence of this natural product as a pair of stable atropo-enantiomers was demonstrated analytically through LC−CD investigations. Preparatively, the racemate resolution succeeded by O-demethylation, derivatization with Mosher's reagent, and chromatographic separation of the resulting diastereomers. The absolute configurations of the atropisomers were assigned by CD spectroscopy in combination with quantum chemical CD calculations at the stage of the alkaloid 3 and by ROESY experiments of the diastereomeric Mosher derivatives. In the root extract of the curry leaf plant Murraya koenigii (Rutaceae), murrastifoline-F (3) was found to exist as a 56:44 mixture in favor of the M-enantiomer, by LC−CD coupling.

As an intermediate in the synthesis of seven further 1-oxygenated 3-C 1 -substituted carbazole alkaloids, mukonine (1) was synthesized in 46% overall yield, starting from indole-3-carbaldehyde (12) with a Horner-Emmons reaction as the crucial step. From 1 , the other desired alkaloids were obtained in high yields. Among them, clausine E (6) and O -demethylmurrayanine (7) were synthesized for the first time.

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The atropo-diastereoselective cleavage of lactone-bridged and thus configurationally unstable biaryls with chiral metal-activated 1-arylethylamines gives axially chiral biaryl amides in good yields and high atropo-diastereomeric ratios of up to 95:5. In this methodology, even the minor not desired rotational isomer can be recycled literally by recyclization back to the configurationally unstable lactone, and renewed stereoselective cleavage. Furthermore, by the use of the corresponding enantiomer of the N-nucleophile, the enantiomeric biaryl product is also attainable from the same lactone precursor (ªatropo-divergenceº). In addition, several methods have been developed to transform the amide function into a methyl or an aminomethylene group. All these options further enlarge the scope and the utility of the method elaborated.