Synthesis of pisiferol revisited; control of stereochemistry in an intramolecular Diels-Alder reaction

Article abstract of DOI:10.1016/0040-4039(94)88378-5

Thermolysis of 4(X=H) gives 6a and 6b(X=H) in a ratio of 1:4 whereas 4 (X=SO₂Ph) gives more of trans-ring junction product 6a(X=SO₂Ph) suitable for the synthesis of pisiferol [ratio 6a: 6b(X=S)₂Ph) = 1.5:1].