Stereoselective synthesis of the C18–C28 fragment of apoptolidin

An efficient, stereocontrolled synthesis of the C18–C28 segment of apoptolidin has been achieved. Key steps are a stannous triflate-mediated aldol reaction, the acylation of a Weinreb amide with an E-alkenyl lithium reagent and the dihydroxylation of a C19–C20 double bond.