Total synthesis of cytotoxin UK-1and AJI9561 (II)

UK-1 and AJI9561 are cytotoxins isolated from Streptomyces sp. Its structure is characteristic of two benzoxazole skeletons, and has been reported to be active in cancer cells such as mouse cell line B16, mouse leukemia cell P388, and human uterine cancer cell HeLa. This paper describes the effective total synthesis of UK-1, AJI9561 using DDQ (2,3-Dichloro-5,6-dicyanobenzoquinoe) or active carbon (Darco KBR), following the first report of synthesis via N-acyl derivatives. In the method via the N-acyl derivative, the yield of benzoxazole synthesis from the condensation reaction of the trisubstituted benzene derivative accompanying the synthesis of AJI9561 was as low as about 23 %. On the other hand, the synthetic yield of the corresponding benzoxazole was significantly improved to 60 % or more by using DDQ or Darco KBR. As a result, with this improved method, the synthesis process was shortened, and total synthesis yield of AJI9561 from 8 steps 11% for the N-acyllation method to 6 steps 30 % for the DDQ or Darco KBR method.