合成路线1

The hydrogenation of pyridineacrylate (I) produced a mixture of the benzyl-protected pyridinepropionate (II) and the debenzylated analogue (III), which were separated by column chromatography. Ester (III) was converted into amide (IV) upon treatment with aqueous ammonia, and further protected with benzyl chloride to afford (V). Cyclization with 1-bromo-2-butanone (VI) in the presence of NaHCO3 furnished indolizidine (VII). This was acylated with benzoyl chloride in boiling benzene to give ketone (VIII), which was reduced to the benzyl derivative (IX) by means of borane-tert-butyl amine complex and AlCl3. Hydrogenolytic deprotection of the benzyl ether of (IX) afforded phenol (X), which was alkylated with methyl bromoacetate and NaH to yield the corresponding esther (XI). Finally, hydrolysis of the methyl ester (XI) with LiOH provided the target carboxylic acid.