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.
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