Patent ID: 8912345

Claim:
A method for preparing a (−)-clausenamide compound represented by formula (I), comprising the following steps: (1) in the presence of an oxidant and a catalyst, trans-cinnamate represented by formula (II) is converted to (2S,3R)-epoxy cinnamate represented by formula (III) through asymmetric epoxidation reaction; the catalyst is fructose-derived chiral ketone represented by formula (IV) or a hydrate of fructose-derived chiral ketone represented by formula (V); wherein, both R 1 and R 2 are any one selected from the group consisting of phenyl, o-methoxyphenyl, m-methoxyphenyl, p-methoxyphenyl, o-methylphenyl, m-methylphenyl, p-methylphenyl, p-fluorophenyl, p-chlorophenyl, p-bromophenyl, o-fluorophenyl, o-chlorophenyl, o-bromophenyl, 3,4,5-trimethoxyphenyl, p-nitrophenyl, and α-naphthyl; R 3 is any one selected from the group consisting of hydrogen, methyl, benzyl, p-methoxybenzyl, and hydroxymethyl; R 4 is any one selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, cyclohexyl, and benzyl; and Ac is acetyl; (2) in the presence of an alkaline compound, amidation reaction takes place between (2S,3R)-epoxy cinnamate represented by formula (III) and a compound represented by formula (VI), to obtain a compound represented by formula (VII); wherein, the definitions of R 1 , R 2 and R 3 are the same as those in formula (I); (3) in the presence of ruthenium trichloride and the oxidant, the compound represented by formula (VII) is converted to a compound represented by formula (VIII) through oxidation reaction; wherein, the definitions of R 1 , R 2 and R 3 are the same as those in formula (I); (4) in the presence of an alkaline compound, the compound represented by formula (VIII) is converted to (−)-clausenamidone represented by formula (IX) through cyclization reaction; wherein, the definitions of R 1 , R 2 and R 3 are the same as those in formula (I); (5) the (−)-clausenamidone represented by formula (IX) is converted to the (−)-clausenamide represented by the formula (I) through reduction reaction.