Synthesis of Cephalostatin Analogues by Symmetrical and Non-Symmetrical Routes

Abstract

The synthesis of the cephalostatin-analogous bis-steroidal pyrazines 6, 27a/b and 41 by the transformation of the C2-symmetrical diketone 6 as a central precursor, as well as the direct preparation of several non-symmetrical bis-steroidal pyrazines by coupling of enamino ketones (5, 40) with vinyl azides (17a/b) is reported. Furthermore, an improved procedure for preparation of the diketone 6 described earlier is presented.