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We describe the synthesis of seven C2‐alkylcarbazoles via a sequence of Buchwald–Hartwig coupling of arylamines with aryl halides followed by oxidative cyclization of the resulting diarylamines. Methyl groups at the positions 4 and 5 were introduced by taking advantage of the ortho‐directed palladation of meta‐pivaloyloxy‐substituted diarylamines and subsequent conversion of the pivaloyloxy to methyl groups through Stille coupling of intermediate triflates. The obtained ethyl‐ and dimethylcarbazoles served as analytical standards for their identification in petroleum samples and source rocks. [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 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]

Using the palladium(II)-catalyzed oxidative cyclization of a diarylamine and the annulation of a dimethylpyran ring by Lewis acid promoted reaction with prenal as key steps, the total syntheses of the 6-oxygenated pyrano[3,2-a]carbazole alkaloids koenine and koenimbine, and of the 6,7-dioxygenated pyrano[3,2-a]carbazole alkaloids koenigine and koenigicine (koenimbidine, koenidine) were achieved. Moreover, these studies led to an improved synthetic route to the 2,6-dioxygenated carbazole alkaloid glycozolidol. Mukonicine, originally published as 6,8-dimethoxypyrano[3,2-a]carbazole, was found to be identical with koenigicine. [ABSTRACT FROM AUTHOR]

We describe a convergent route to 5,11-dihydroindolo[3,2-b]carbazoles using a twofold oxidative cyclization as key step. The method has been applied to the synthesis of a precursor for malasseziazole A and to the first total synthesis of malasseziazole C. [ABSTRACT FROM AUTHOR]

Using a palladium(II)-catalyzed oxidative cyclization of an N,N-diarylamine, we have achieved the total synthesis of the 2,8-dioxygenated carbazole alkaloids carbalexin B, clausine A, clauszoline M, and 2,8-dihydroxy-3-methylcarbazole. [ABSTRACT FROM AUTHOR]

The pentahalogenated 2-arylpyrrole-type alkaloids pentabromopseudilin and pentachloropseudilin represent a new class of isoform-specific allosteric inhibitors of myosin ATPase. Herein, we describe an application of the silver(I)-catalyzed cycloisomerization of N-(homopropargyl)toluenesulfonamides to the total syntheses of these natural products and several non-natural analogues. Moreover, we examine the inhibitiory effect of pentahalogenated pseudilins on myosin ATPase activity. [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]

We report the first total synthesis of murrastifoline B and an improved route to murrastifoline F using a twofold palladiumcatalyzed Buchwald-Hartwig amination as key step. The monomeric carbazole and the biaryl precursor are also prepared via palladium-catalyzed coupling reactions. [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]

Consecutive palladium-catalyzed C-N and C-C bond formation provides an efficient route to the 1,7,8-trioxygenated carbazole alkaloid murrayastine. [ABSTRACT FROM AUTHOR]

We describe the synthesis of three hexahalogenated 1,1′-dimethyl-2,2′-bipyrroles using an efficient silver(I)-catalyzed cyclization as key step. [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]

Highly efficient syntheses of the free radical scavenger carazostatin and its O-methyl derivative are described using cyclohexa-1,3-diene and 2-heptyl-4-methoxy-3-methylaniline as starting materials and iron-mediated oxidative cyclizations as key-steps. [Copyright &y& Elsevier]

The sequence of palladium(0)-catalyzed amination and palladium(II)-catalyzed oxidative formation of the biaryl bond provides a direct route to the 1,7-dioxygenated tricyclic carbazole alkaloids clausine Q and clausine R. [ABSTRACT FROM AUTHOR]

The tetracyclic pyrido[4,3-b]carbazole olivacine and four of its oxygenated derivatives have been synthesized by a late-stage palladium-catalyzed Heck-type cyclization of the pyrrole ring as a key step. In a test for the inhibition of the growth of Mycobacterium tuberculosis, 9-methoxyolivacine showed the most significant inhibitory activity against Mycobacterium tuberculosis, with an MIC90 value of 1.5 μM. [ABSTRACT FROM AUTHOR]

Condensation of aromatic aldehydes with arylamines to form Schiff bases, and subsequent addition of trimethylsilylpropargylmagnesium bromide, leads to homopropargylamines which on silver(I)-promoted oxidative cyclization affords 1,2-diarylpyrroles. [ABSTRACT FROM AUTHOR]

An efficient total synthesis of (±)-lavanduquinocin, a potent neuronal cell protecting alkaloid from Streptomyces viridochromogenes, is reported. Key-steps are an iron-mediated one-pot construction of the carbazole framework and a nickel-mediated coupling reaction. [ABSTRACT FROM AUTHOR]