Total Syntheses of Murrayamine E, I, and K

Abstract

We describe efficient synthetic routes to murrayamine A (mukoenine C), O-methylmurrayamine A, mahanine, O-methylmahanine, and murrayamine D and the first total syntheses of murrayamine E, I, and K. Key steps are a palladium-catalyzed construction of the carbazole framework and an annulation of the pyran ring, which is either catalyzed by phenylboronic acid or promoted by a Lewis acid.

Asymmetric copper-catalyzed C-N cross-couplings induced by visible light

“…As a model coupling process, we examined the reaction of carbazole, a heterocycle that occurs in bioactive molecules, including N- tert -alkyl-substituted compounds (20,21), with an α-halocarbonyl compound, a class of electrophiles that has not previously been employed in photoinduced, copper-catalyzed cross-couplings. Upon investigating a range of reaction parameters, we discovered that irradiation of the cross-coupling partners at –40 °C for 16 hours in the presence of CuCl, a chiral phosphine ( L* ), and a Brønsted base provides the desired product in 95% yield and 95% enantiomeric excess (ee) (Fig.…”

Total Synthesis of Fontanesine B and Its Isomer: Their Antiproliferative Activity against Human Colorectal Cancer Cells

“…The residue was extracted with AcOEt/CHCl 3 (2 × 300 mL, v/ v 5 : 1) and washed with water, brine, and dried over MgSO 4 . The solvent was removed, and the residue was purified by recrystallization with Et 2 O to give 11 as colorless powder ( N-(2,2-Dimethyl-2H-1-benzopyran-6-yl)acetamide (12). A solution of 11 (14.1 g, 60 mmol) and p-toluenesulfonic acid (1 g, 6 mmol) in benzene/toluene (300 mL, v/v 1:1) was stirred for 5 h under reflux conditions and then cooled to room temperature.…”

Synthesis of Tetranuclear Palladium(II) Complexes and Their Catalytic Activity for Cross‐Coupling Reactions

“…[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Herein, we report the synthesis of the 1,1'-coupled bis-2-hydroxy-3-methylcarbazole (1), the methoxy-substituted 1,1'-bicarbazole-2,2'-diols 2-5,b isglybomineB ( 6), the bi(pyrano[3,2-a]carbazoles) 7-9,a nd the 2,2'-bicarbazoles 10-12 by oxidative coupling of the corresponding monomeric carbazole alkaloids (Figure 1a nd Figure 2). The carbazoles are availableb yo ur molybdenum-mediated, [25,26] iron-mediated [27][28][29] andp alladium-catalyzed [30][31][32][33][34][35][36][37][38][39][40][41] approaches. The present report complementso ur recent syntheses of methylenebridged biscarbazolesb ased on an Ullmann-typec oupling of carbazole units as key step.…”

“…[10,18,[46][47][48][49] Our approach using aB uchwald-Hartwig coupling of the aniline 13 and iodobenzene followed by palladium(II)-catalyzed oxidative cyclization and methyl ether cleavage provided 2-hydroxy-3-methylcarbazole (14)i nt hree steps and 85 %o verall yield on gram scale. [40,48,49] Using 14 as model compound, we screened the performance of variousr eagents for the oxidative coupling to the 1,1'-bicarbazole 1 ( Table 1). Treatment of 14 with ac opper(II)-TMEDA (N,N,N',N'-tetramethylethylenediamine) complexu nder air,amethod previously used by Koga and co-workersf or the oxidative coupling of b-naphthols, [50] provided the 1,1'-bicarbazole 1 in only 12 %y ield.…”