The 3-aryl-3-aminopropionic acid (II) was prepared by Knoevenagel condensation of 4-(1-naphthyl)benzaldehyde (I) with malonic acid in the presence of ammonium acetate. Subsequent esterification of (II) by means of thionyl chloride and methanol afforded the methyl ester (III). Coupling of amino ester (III) with N-Boc-glycine (IV) by means of TBTU and HOBt furnished amide (V). After acidic Boc group cleavage, the resultant dipeptide ester (VI) was acylated with 4-(4-methylpyridin-2-ylamino)butyric acid (VII), yielding tripeptide ester (VIII). The methyl ester group of (VIII) was finally hydrolyzed by NaOH in aqueous dioxan.

The 3-aryl-3-aminopropionic acid (II) was prepared by Knoevenagel condensation of 4-(1-naphthyl)benzaldehyde (I) with malonic acid in the presence of ammonium acetate. Subsequent esterification of (II) by means of thionyl chloride and methanol afforded the methyl ester (III). Coupling of amino ester (III) with N-Boc-glycine (IV) by means of TBTU and HOBt furnished amide (V). After acidic Boc group cleavage, the resultant dipeptide ester (VI) was acylated with 4-(4-methylpyridin-2-ylamino)butyric acid (VII), yielding tripeptide ester (VIII). The methyl ester group of (VIII) was finally hydrolyzed by NaOH in aqueous dioxan.