Total synthesis of calothrixin B and its analogs

Article abstract of DOI:10.1002/ejoc.201301524

The total synthesis of calothrixin B and its analogs was achieved starting from 2-methylindole. The synthesis involved an electrocyclization of 2-nitroarylvinyl-3-phenylsulfonylvinylindoles as a key step to give 2-nitroaryl-4-methoxy-3-methylcarbazoles. Oxidation of these compounds followed by reductive cyclization led to N-phenylsulfonylquinocarbazoles. These quinocarbazoles underwent hydrolysis and aerial oxidation in one pot to give the target compounds. A linear synthesis of calothrixin B and its analogs has been established from commercially available 2-methylindole. The thermal electrocyclization of 2-nitroarylvinyl-3-phenylsulfonylindole was a key step in the synthesis. The synthesis of calothrixin B and its analogs was achieved in 12-22 % overall yield over twelve steps. Copyright