合成路线1

In a further procedure, pyridine-2,3-dicarboxylic acid (L) was esterified with MeOH and SOCl2 and then oxidized to the N-oxide (LI), which by treatement with POCl3 gave chloropyridine (LII). Then, substitution of the halogen atom of (LII) for a butyl group using n-BuLi in the presence of ZnCl2 and palladium catalyst provided butylpyridine (LIII). Saponification of the methyl esters, followed by reaction with Ac2O gave cyclic anhydride (LIV). This was condensed with organozinc reagent (LV) to give ketone (LVI). After activation of (LVI) with carbonyl diimidazole, condensation with the lithium enolate of ethyl acetate, followed by cyclization produced cyclopentenone (LVII). This was condensed with Grignard reagent (XXIV) to give (LVIII) and then reduced with Zn and HCl and isomerized in the presence of EtONa to provide (LIX) as a racemic mixture.