Synthesis of Spirastrellolide A Fragments for Structure Elucidation

A stereocontrolled synthesis of two diastereomeric C1-C22 fragments of spirastrellolide A consistent with reported spectroscopic data has been achieved to aid in a complete configurational assignment of this structurally novel and potent antimitotic natural product. A highly convergent coupling of two enantiomeric C1-C10 methyl ketone fragments with an enantiopure C11-C22 spiroketal ­aldehyde produced the C1-C22 fragments with a longest linear sequence of 13 steps from commercially available starting materials.