New Key Building Block for Ixabepilone from R-(-)-Carvone.

A synthetic approach is described for the transformation of R-(-)-carvone to methyl (2Z,5S,6E)-5-[(tert-butoxycarbonyl)amino]-2,6-dimethyl-7-(2-methyl-1,3-thiazol-4-yl)hepta-2,6-dienoate, the key building block for the convergent synthesis of the known antitumor macrolactam ixabepilone. The synthetic sequence includes 10 stages, where the key stage is Curtius rearrangement. Optimal conditions have been found for that rearrangement. [ABSTRACT FROM AUTHOR]