First total synthesis of (4R,5R,11S) and (4R,5R,11R)-isocladospolide B

The two enantiomers of natural products (4<em>S</em>, 5<em>S</em>, 11<em>R</em>)-and (4<em>S</em>, 5<em>S</em>, 11<em>S</em>)-<em>iso</em>-cladospolide B have been synthesized and their structures unambiguously confirmed by X-ray crystallographic analysis. Key steps of the synthesis include the use of tri-O-acetyl-D-glucal as precursor for a chiral furan diol which, after side chain transformation, underwent singlet oxygen oxidation to afford the target butenolide