合成路线1

Pyridone (XII) was converted to its dianion with LDA and then alkylated with propyl bromide to give the butyl pyridone (XIII). This was converted into bromopyridine (XIV) by subsequent treatment with PBr3. The nitrile group of (XIV) was then reduced to aldehyde (XV) using diisobutylaluminum hydride. The aldehye (XV) underwent a Heck reaction with tert-butyl acrylate (XVI) using tri-o-tolylphosphine and a palladium catalyst to provide unsaturated ester (XVII). Further condensation of the aldehyde group of (XVII) with (S,S)-pseudoephedrine (XVIII) produced the chiral oxazolidine (XIX). Alcohol (XI) was then protected as the silyl ether (XXI) using tert-butyldimethylsilyl chloride. After its conversion to the organolithium reagent with tert-butyllithium, addition to pyridyl acrylate (XIX) gave intermediate (XXII), and further acidic work-up removed the chiral auxiliary to afford aldehyde (XXIII).