AN IMPROVED DIENOPHILE-INDUCED ACCESS TO ENANTIOPURE 2,4-DIDEOXYSUGARLACTONES VIA HETERO-DIELS-ALDER REACTION - SYNTHESIS OF THE (-LACTONEMOIETY OF COMPACTIN())

Polystereocontrolled access to 4-type heterocycloadducts was consisten tly improved by using a new 4-oxy-substituted 1-oxabutadiene, methyl ( E)-tert-butoxymethylenepyruvate (1c). Obtained in both enantiomeric fo rms with high diastereomerical purity, these adducts led to diprotecte d 2,4-dideoxyglucose 10 and gluconolactone 12 in both L and D series i n high yields. Epimer ization of (-)-12 via ntramolecular Mitsunobu in version gave a straightforward access to the lactone moiety (+)-16 of compactin.