The design, synthesis and evaluation of A,C,D-ring analogs of the fungal metabolite K-76 as complement inhibitors: a potential probe for the absolute stereochemistry at position 2

In an attempt to synthesize stereochemically pure new A, C, D-ring analogs of the natural product complement inhibitor K-76, compounds (20–24) were prepared and the representative one (23) was evaluated for its ability to inhibit complement-mediated erythrocyte lysis in both the classical and alternative pathways. Compounds synthesized as part of this study suggest that the terpenoid diol component of K-76 may not be essential for complement inhibition.