Enantioselective total synthesis of (+)-6-epi-mevinolin and its analogs. Efficient construction of the hexahydronaphthalene moiety by high pressure-promoted intramolecular Diels-Alder reaction of (R,2Z,8E,10E)-1-[(tert-butyldimethylsilyl)oxy]-6-methyl-2,8,10-dodecatrien-4-one

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, (+)-6-epi-mevinolin (2a) and (+)-6-epi-4a,5-dihydromevinolin (2b), were prepared by combining two nonracemic units, phosphonate 3 and decalin 4, which were prepared from enantiopure 3-substituted pentanedioic acid monoesters 5a and 5b, respectively. Each acid was synthesized from cyclic anhydrides 7a and 7b by diastereoselective ring opening by means of (S)-benzyl mandelate as a common chiral auxiliary. The construction of decalin moiety 4 was accomplished by asymmetric intramolecular Diels-Alder (IMDA) reaction of nonracemic trienone 6 bearing a methyl group as a chiral controller. The IMDA diastereoselectivity of trienone 6 is discussed in terms of the configuration of(E)- and (Z)-dienophiles which are activated by an endogenous carbonyl group. The IMDA reaction of(R)-(Z)-6 under high pressure is highly selective and gives cis-decalins exclusively with preferential formation of 4 over 16. The inhibitory activity of (+)-6-epi-mevinolin (2a) and several analogs against HMG-CoA reductase was compared with mevinolin (1b). (+)-6-epi-Mevinolin (2a) was shown to be half as potent as mevinolin (1b) while (+)-6-epi-4a,5-dihydromevinolin (2b) was as potent as mevinolin.