Total syntheses of carazostatin and hyellazole by allene-mediated electrocyclic reaction

Total Synthesis of (&plusmn;)-Carquinostatin A, and Asymmetric Total Synthesis of (<i>R</i>)-(−)-Carquinostatin A and (<i>S</i>)-(+)-Carquinostatin A

“…18,19) To synthesize the highly functionalized carbazole alkaloid, we have constructed a carbazole framework based on an allenemediated electrocyclic reaction with a tautomeric process involving the indole 2,3-bond. [20][21][22][23][24][25][26][27][28][29][30] In 2007, we reported the lipase-QLM catalyzed enantioselective synthesis of (R)-(−)-6-desprenylcarquinostatin and its (S)-(+)-enantiomer from 1-acetonyl-3-ethoxy-2-methylethoxycarbazole (5) (Fig. 1), which was prepared using an allene-mediated electrocyclic reaction.…”

Lipase-Catalyzed Asymmetric Synthesis of Desprenyl-carquinostatin A and Descycloavandulyl-lavanduquinocin

“…We recently reported the synthesis of the highly substituted carbazole alkaloids, carazostatin 9) and carbazoquinocins, 9,10) by the construction of the appropriate carbazole framework based on the allene-mediated electrocyclic reaction of the 6p-electron system involving the indole 2,3-bond. In the present paper, we describe the asymmetric synthesis of 6-desprenyl-carquinostatin A (6-descycloavandulyllavanduquinocin) 3, which is a common carbazole framework of both alkaloids, based on a lipase-catalyzed esterification using a racemic alcohol 6 for the determination of the absolute stereochemistry of 3.…”

“…In the present paper, we describe the asymmetric synthesis of 6-desprenyl-carquinostatin A (6-descycloavandulyllavanduquinocin) 3, which is a common carbazole framework of both alkaloids, based on a lipase-catalyzed esterification using a racemic alcohol 6 for the determination of the absolute stereochemistry of 3. We chose the 3-ethoxy-2-methyl-1-(trifluoromethylsulfonyloxy)carbazole (4), 9,10) as a starting material, which was prepared in a six-step sequence from 3-iodoindole-2-carbaldehyde by the application of our methodology, as shown in the retrosynthetic Chart 1.…”

“…Total syntheses of these alkaloids have recently been developed by the Knölker group. [3][4][5][6][7][8] The transition metalmediated and -catalyzed methodologies for the construction of the carbazole framework have been efficiently employed.Throughout the course of this study, we have been interested in the synthetic development of biologically active condensed-heteroaromatic compounds, including natural products, by the thermal electrocyclic reactions of either conjugated hexatriene [9][10][11][12][13][14][15][16][17] or monoazahexatriene 18) systems incorporating one double bond from an aromatic or heteroaromatic portion. We recently reported the synthesis of the highly substituted carbazole alkaloids, carazostatin 9) and carbazoquinocins, 9,10) by the construction of the appropriate carbazole framework based on the allene-mediated electrocyclic reaction of the 6p-electron system involving the indole 2,3-bond.…”

Química de alcaloides carbazólicos: síntese de Claurailas e de biblioteca de análogos estruturais

“…Visando a obtenção de 1, inicialmente foi realizada a síntese do triflato de vanilina (Choshi et al, 1996), que em seguida foi utilizado na reação de aminação de …”