Total synthesis of 5-N-acetylardeemin and amauromine:: Practical routes to potential MDR reversal agents

The total synthesis of the title compounds has been accomplished. The key step involves the kinetic stereoselective conversion of 19 --> 20. The synthesis of 20 represents for the first time a direct method for constructing exo-pyrroloindoles from protected tryptophans in a highly diastereoselective manner. This step was followed by reverse prenylation (see conversion of 20 --> 27). Using the methodology worked out for the titled compounds, a practical synthesis of several promising MDR reversal agents was possible. Biological data that provided the basis for selection of candidates for advanced study are presented. Preliminary profiling of the zones of the molecules that are responsive to changes while still retaining MDR reversal ability are described. On the basis of these findings, compounds 2, 50, and 51 were selected for more extensive biological follow-up.