合成路线1

Condensation of L-phenylalanine methyl ester (V) with benzaldehyde gave aldimine (VI). Then, alkylation of (VI) with allyl bromide in the presence of LDA, and subsequent imine hydrolysis afforded the racemic alpha-allylphenylalanine methyl ester (VII), which was protected as the N-Boc derivative (VIII) upon treatment with Boc2O. Ozonolysis of the olefin group of (VIII), followed by reductive workup with Me2S yielded the aldehyde ester (IX). This was cyclized with hydrazine, affording pyridazinone (X), which was further hydrogenated over PtO2 to give (XI). The 1,3-dipolar cycloaddition of the iminium ion (XII), formed by treatment of (XI) with formaldehyde, and boiling ethyl acrylate furnished a mixture of pyrazolopyridazines (XIIIa-b). After chromatographic isolation of the racemic cis amino ester, its hydrolysis with LiOH yielded carboxylic acid (XIV). Coupling of (XIV) with aminoalcohol (IVa-b) using EDC and HOBt provided the corresponding amide (XVa-d) as a mixture of 4 diastereomers. Oxidation of the secondary alcohol of (XVa-d) with Dess-Martin periodinane gave the diastereomeric ketones (XVIa-b). Then, deprotection of (XVIa-b) by means of trifluoroacetic acid, followed by separation of the isomers by HPLC furnished the title compound.