unique biological activity, make the natural occurring apoptolidin (1) a challenging synthetic target. The retrosynthetic analysis revealed five key building blocks-three for the construction of the macrolide ring B and two prospective pendant saccharide units-which were synthesized in a highly convergent manner and then connected. Apoptolidin's rather labile nature proved particularly challenging in
Derivatives of apoptolidin, including skeletal homologues, are potent and selective apoptosis-inducing agents which, unlike apoptolidin, do not undergo isomerization under physiological conditions. These compounds exhibit antitumor properties, often superior to those of apoptolidin, and as such can be used in the treatment of cancer and other hyperproliferative disorders.