188037-54-9Relevant articles and documents
Total Syntheses of Carazostatin, Hyellazule, and Carbazoquinocins B-F
Choshi, Tominari,Sada, Takuya,Fujimoto, Hiroyuki,Nagayama, Chizu,Sugino, Eiichi,Hibino, Satoshi
, p. 2535 - 2543 (2007/10/03)
Total syntheses of carazostatin (1), hyellazole (2a), and carbazoquinocins B-F (3b-f) have been completed. The cross-coupling reaction between 3-iodoindole 8 and vinylstannane 11b gave the 3-alkenylindole 7. Treatment of 7 with ethynylmagnesium bromide, followed by etherification of the resulting alcohol 12 with MOMCl, yielded the 3-alkenyl-2-propargylindole 6. The compound 6 was treated with t-BuOK in t-BuOH at 90°C to obtain the desired carbazoles 4 together with the N-deprotected carbazole 13 through an allene-mediated electrocyclic reaction. The carbazole 13a, derived from 4a or 4c, was converted into the triflate 24 in two steps. The triflate 24 was subjected to the Suzuki cross-coupling reaction with either 9-heptyl-9-BBN or phenylboronic acid in the presence of a palladium catalyst to produce the 1-heptylcarbazole 25a and the 1-phenylcarbazole 25b. Cleavage of the ether bond of 25a yielded carazostatin (1). Cleavage of the ether bond of 25b followed by O-methylation gave hyellazole (2a). Oxidation of carazostatin (1) with benzene seleninic anhydride afforded carbazoquinocin C (3c). In a similar way, carbazoquinocins B and D-F (3b,d-f) were synthesized, respectively.
