Collective and Diverted Total Synthesis of the Strasseriolides: A Family of Macrolides Endowed with Potent Antiplasmodial and Antitrypanosomal Activity

The strasseriolide macrolides show promising in vitro and in vivo activities against P. falciparum and T. cruzi, the parasites causing malaria and Chagas disease, respectively. However, the as yet poor understanding of structure/activity relationships and the fact that one family member proved systemically toxic for unknown reasons render a more detailed assessment of these potential lead compounds difficult. To help overcome these issues, a collective total synthesis was devised. The key steps consisted of a ring closing alkyne metathesis (RCAM) reaction to forge a common macrocyclic intermediate followed by a hydroxy-directed ruthenium catalyzed trans-hydrostannation of the propargyl alcohol site thus formed. The resulting alkenyltin derivative served as the central node of the synthesis blueprint, which could be elaborated into the natural products themselves as well as into a set of non-natural analogues according to the concept of diverted total synthesis. The recorded biological data confirmed the potency of the compounds and showed the lack of any noticeable cytotoxicity. The "northern" allylic alcohol subunit was recognized as an integral part of the pharmacophore, yet it provides opportunities for chemical modification.