A [2 + 2 + 2]-Cycloaddition Approach toward 6-Oxa-allocolchicinoids with Apoptosis-Inducing Activity

Following an A → ABC strategy, a new synthesis of 6-oxa-allocolchicinoids was developed exploiting a microwave-promoted Co- or Rh-catalyzed intramolecular [2 + 2 + 2]-cycloaddition (alkyne cyclotrimerization) as a key step. The approach opens a short and efficient access to a variety of novel compounds, some of which were found to exhibit significant and selective apoptosis-inducing activities against BJAB tumor cells.