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The relative configuration of the marine sesquiterpenoid oxyfungiformin, isolated from the soft coral Capnella fungiformis, was confirmed by synthesis using the natural product guaiol as chiral precursor. The absolute configuration of oxyfungiformin could be assigned by combination of X‐ray diffraction and comparison of the values for the specific optical rotation. Oxyfungiformin and a diastereoisomer showed cytotoxic activity in cells originating from cancers of the lung, breast, and cervix. [ABSTRACT FROM AUTHOR]

We describe the first total synthesis of the recently discovered pyrano[3,2- a ]carbazole alkaloid clausenalansine A. The synthetic strategy for the construction of this formylpyrano[3,2- a ]carbazole is based on a sequence of Buchwald–Hartwig coupling, palladium(II)-catalyzed oxidative cyclization, Lewis acid promoted annulation of the pyran ring, and chemoselective oxidation of a methyl to a formyl group. [ABSTRACT FROM AUTHOR]

We describe a short and efficient synthetic route to euchrestifoline. Key steps of our approach are the iron(III)‐catalyzed Wacker‐type oxidation of a chromene derivative with hexadecafluorophthalocyanine‐iron (FePcF16) as catalyst, a palladium(0)‐catalyzed Buchwald–Hartwig amination, and the final palladium(II)‐catalyzed oxidative cyclization of the resulting diarylamine to the natural product. [ABSTRACT FROM AUTHOR]

We describe the first total synthesis of the pyrano[3,2-a]carbazole alkaloid 7-isovaleryloxy-8-methoxygirinimbine, using a palladium(II)-catalyzed double C-H-bond activation for construction of the carbazole framework and a phenylboronic acid catalyzed annulation of the pyran ring as key steps. [ABSTRACT FROM AUTHOR]

Abstract: We describe the synthesis of 1,1′‐ and 2,2′‐bicarbazoles by oxidative homocoupling of 2‐ and 1‐hydroxycarbazoles. The oxidative coupling using catalytic amounts of F16PcFe can be applied to both groups of substrates. Although F16PcFe generally provides the best yields for the synthesis of 1,1′‐bicarbazoles, di‐tert‐butyl peroxide affords better results for the 2,2′‐bicarbazoles. In our study, we have achieved the first syntheses of the biscarbalexines A–C, bisglybomine B, 2,2′‐dihydroxy‐7,7′‐dimethoxy‐3,3′‐dimethyl‐1,1′‐bicarbazole, bispyrayafoline C, and bisisomahanine. The iron‐catalyzed coupling of koenigine led to an improved synthesis of 8,8′′‐biskoenigine and afforded an unprecedented decacylic product. Oxidative coupling of 1‐hydroxycarbazoles led to bisclausenol, and to the first total syntheses of bismurrayafoline B and D. [ABSTRACT FROM AUTHOR]

We describe a regioselective synthesis of 4- or 5-substituted carbazoles by oxidative cyclisation of meta-oxygen-substituted N-phenylanilines. Using the regiodirecting effect of a pivaloyloxy group, we prepared 4-hydroxycarbazole, a precursor for the enantiospecific synthesis of the β-adrenoreceptor antagonists (−)-( S)-carazolol ( 5) and (−)-( S)-carvedilol ( 6). Regioselective palladium(II)-catalysed cyclisation of different diarylamines led to total synthesis of glycoborine ( 7) and the first total syntheses of the phytoalexin carbalexin A ( 8), glybomine A ( 9) and glybomine B ( 10). For glybomine B ( 10), a 5-hydroxycarbazole was converted into the corresponding triflate and utilized for introduction of a prenyl substituent. [ABSTRACT FROM AUTHOR]

The DIBAL-H promoted reductive pyran ring opening of dialkylpyrano[3,2- a]carbazoles provides a direct access to a broad range of prenyl- and geranyl-substituted carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila-E, 7-hydroxyheptaphylline, 7-methoxyheptaphylline, mukoenine-B (clausenatine-A), mukoenine-A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine-A, and isomurrayafoline-B. [ABSTRACT FROM AUTHOR]

The boronic acid-catalyzed annulation of citral opens up a short route to oxygenated cyclized monoterpenoid pyranocarbazole alkaloids. Thus, murrayamine-D is available in only three steps and 55% overall yield from the corresponding carbazole precursor. [ABSTRACT FROM AUTHOR]

We describe the synthesis of the naturally occurring 2,7-dioxygenated formylcarbazole alkaloids 7-methoxymukonal, 7-methoxy- O-methylmukonal, and the murrayalines A-C. The carbazole framework was constructed by a Buchwald-Hartwig amination and a subsequent palladium(II)-catalyzed oxidative cyclization. [ABSTRACT FROM AUTHOR]

A surprisingly selective, non‐enzymatic kinetic resolution of readily available, racemic β‐chiral ketones enabled the title process, which was applied to a rapid synthesis of several bioactive flavanones in virtually enantiopure form (see scheme; MOM=methoxymethyl, Ts=p‐toluenesulfonyl). [ABSTRACT FROM AUTHOR]

We have developed a highly efficient route to 2-hydroxy-3-methylcarbazole ( 1) via a palladium-catalyzed construction of the carbazole skeleton. Using 1 as relay compound, different methods for annulations of pyran rings by reaction with terpenoid building blocks have been tested. The Lewis acid promoted reaction of 1 with prenal ( 21) opened up an efficient route to girinimbine ( 3) and the corresponding reaction with citral ( 25) afforded mahanimbine ( 5). Oxidation of compounds 3 and 5 provided murrayacine ( 4) and murrayacinine ( 6). Following the biogenetic proposal, mahanimbine ( 5) has been exploited for efficient biomimetic syntheses of the cyclized monoterpenoid pyrano[3,2- a]carbazole alkaloids cyclomahanimbine ( 7), mahanimbidine ( 8) and bicyclomahanimbine ( 9). The interconversions of 5, 7, 8 and 9 are described and mechanistic implications are discussed. Structural assignments are unambiguously verified by X-ray crystal structure determinations. Moreover, cyclomahanimbine ( 7) was transformed into murrayazolinine ( 10) and exozoline ( 11). [ABSTRACT FROM AUTHOR]

Why take things one step at a time? Aryl–pyran‐linked biscarbazole alkaloids of the murrafoline group (see crystal structure of murrafoline A; dark gray: C, red: O, blue: N) were accessed readily by a novel domino reaction sequence involving Sonogashira coupling, a Claisen rearrangement, and electrocyclization. The one‐pot procedure enables the straightforward synthesis of these structurally challenging alkaloids in only a few steps. [ABSTRACT FROM AUTHOR]

Using an iron-mediated construction of the carbazole framework, the first synthesis of streptoverticillin is described and the absolute configuration of the natural product is confirmed. The synthesis exploits a novel oxygen-mediated aromatization of tricarbonyliron-coordinated dihydrocarbazoles. Moreover, non-natural (R)-streptoverticillin is prepared for comparison. [ABSTRACT FROM AUTHOR]

A space filling model of the X‐ray structure of the pyrano[3,2‐a]carbazole alkaloid mupamine is shown. Its synthesis, which involves the boronic acid‐catalyzed annulation of citral, is described in the Communication by H.‐J. Knölker et al. on page 8536 ff. [ABSTRACT FROM AUTHOR]