Total Synthesis of Oxazole- and Cyclopropane-Containing Epothilone B Analogues by the Macrolactonization Approach
作者:K. C. Nicolaou、Francisco Sarabia、M. Ray V. Finlay、Sacha Ninkovic、N. Paul King、Dionisios Vourloumis、Yun He
DOI:10.1002/chem.19970031212
日期:1997.12
AbstractIn order to probe structure‐activity relationships in the epothilone area, two series of epothilone B analogues have been designed and synthesized. The first series containing an oxazole moiety in place of a thiazole on the side chain was constructed by utilizing key intermediates 7–9 or 10, 12, and 13 (Scheme 1), whereas the second series containing an ethano group instead of the gem‐dimethyl group at position 4 was synthesized from fragments 42 and 43. A Yamaguchi‐type macrolactonization reaction was used to construct the macrocycle from a secoacid, which was assembled, in both cases, by means of a) an aldol reaction, b) an Enders alkylation, and c) a Wittig‐type reaction. This convergent strategy provided access to oxazole analogues 2,4,29–32 and 4,4‐ethano derivatives 3,40,60–63 for biological studies.