New approach to 3-oxygenated carbazoles. Synthesis of hyellazole and 4-deoxycarbazomycin B

Abstract

3-Oxygenated carbazoles are prepared in 4 steps from 1 -acetyl-2-methoxy-1,2-dihydroindol-3-one 6 by Wittig reaction with phosphonium ylides 10 to afford the 3-alkylindoles 11, followed by silylation to the silyl enol ethers 12. Electrocyclic reaction of the enol ethers 12 followed by desilylation give the 3-hydroxycarbazoles 15. The carbazoles 15a, b were converted into the carbazole alkaloid hyellazole 1 and 4-deoxycarbazomycin B 2c, respectively.