ASYMMETRIC DIELS-ALDER REACTION OF OPTICALLY-ACTIVE ALPHA-(2-EXO-HYDROXY-10-BORNYL)SULFINYLMALEIMIDES AND ITS APPLICATION TO OPTICALLY-ACTIVE 5-FUNCTIONALIZED PYRROLINES VIA RETRO-DIELS-ALDER REACTION

Optically pure sulfinylmaleimides 1 have been synthesized. The Diels-Alder reactions of the sulfoxides 1 with various dienes showed high diasteroselectivity. Regioselective reduction of the adducts 4c and 6c followed by desulfinylation afforded the gamma-hydroxy lactams 17 and 27, respectively. N-Acyliminium additions using compounds 17 and 27 proceeded diastereoselectively to give gamma-alkyl lactams 23 and 29 by virtue of its conformationally rigid, bicyclo[2.2.1]- and 7-oxabicyclo[2.2.1]-heptene moiety. respectively. The use of compound 29 allows a simple preparation of chirally 5-functionalised Delta(3)-pyrrolin-2-ones of high optical purity such as compound 25 via retro-Diels-Alder reaction, whereas the thermal cycloreversion of adduct 23 required such forcing conditions as flash vacuum pyrolysis.