(±)-1-Methyl-7-oxabicyclo[2.2.1]heptan-2-one (1) is a versatile chiral building block for terpenoids. It could be applied in total synthesis of eudesmanes, agarofurans and norcarotenoids. Compound (±)-1 was reduced to alcohol (±)-2. Compound (±)-2 was esterified with commercial available optically pure (S)-(+)-mandelic acid. The diastereomeric ester mixture was separated with preparative HPLC method. After oxidation of the saponified products of diastereomeric ester (+)-4 and (+)-5 respectively, both optically pure enantiomers of compound 1 were prepared for the first time in four steps with an overall yield of 70%. The absolute configurations of (+)-1 and (-)-1 were determined as (+)-(1R,4S)-1-methyl-7-oxabicyclo[2.2.1] heptan-2-one and (-)-(1S,4R)-1-methyl-7-oxabicyclo[2.2.1] heptan-2-one.
3-Oxo-11,12,13-trihydroxyeudesm-4-ene(1) was a highly oxygenated natural eudesmane isolated from traditional herbal medicine with an antiphlogostic and spasmolytic activity.For the purpose of pharmacological activity research on natural product 1 and its derivatives,a facile total synthesis of compound 1 starting from(+)-dihydrocarvone(2) was completed in an overall yield of 24%.The structures of all intermediates and product 1 were confirmed via 1H NMR,13C NMR,MS and IR techniques.The NMR data of compound 1 are in agreement with those of natural products.
