(SS)-2-(P-TOLYLSULFINYL)NORBORNENO-P-BENZOQUINONES - A NEW-TYPE OF FACIALLY PERTURBED ENANTIOPURE QUINONES

The syntheses and asymmetric Diels-Alder reactions of (SS)-2-(p-tolyls ulfinyl)norboreno-p-benzoquinones 10 and 11 with cyclopentadiene are r eported. The cycloadditions allowed the highly stereoselective obtenti on of the four possible endo adducts 12-15, optically pure synthetic e quivalents of norborneno-p-benzoquinone-cyclopentadiene bisadducts. Th e detailed study of the H-1-NMR spectra of the adducts pointed out the anisotropic effects exerted by the sulfinyl moiety on the spectroscop ic behavior of these rigid systems. In all cases, the pi-facial select ivities were fully controlled by the sulfinyl group being possible to reverse the diastereoselection in thermal conditions and in the presen ce of ZnBr2. The stereoselective synthesis of the cage compound 5, pre cursor of garudane, was achieved from cycloadduct endo-syn-13.