ENANTIOSELECTIVE SYNTHESIS OF (-SHIKIMIC ACID AND (+)-5-EPI-SHIKIMIC ACID BY ASYMMETRIC DIELS-ALDER-REACTION OF (S)-ALPHA-SULFINYLACRYLATES())

Enantiopure (S) benzyl and t-butyl 2-p-tolylsulfinylpropenoates (1 and 2) were readily prepared by Mannich condensation of (R) p-tolylsulfin ylacetates (CH2O+Me2NH), followed by in situ nitrogen quaternization. These new chiral dienophiles reacted with furan at high pressures (4-1 3 Kbar) at rt to afford mainly a 2:1 mixture of both endo adducts (end o-B+endo-A). Enantiopure endo-4B and endo-4A were stereoselectively tr ansformed into (+)-shikimic acid and (+)-5-epi-shikimic acid respectiv ely, by dihydroxylation of the double bond, removal of the sulfinyl gr oup, basic opening of the oxabicyclic skeleton and hydrolysis of the e ster moiety. (C) 1997 Elsevier Science Ltd.