Under stirring conditions, β-alanine (β-Ala, 0.5 g, 6.61 mmol) was dissolved in 10% aqueous Na2CO3 solution (12 ml) in a 50 ml flask. The flask was cooled in an ice bath followed by slow dropwise addition of Fmoc-Cl (1.45 g, 5.61 mmol) in dioxane (10 ml) solution. The reaction mixture was stirred continuously for 4 hours at room temperature. After completion of the reaction, the aqueous phase layer was separated by adding water (80 ml) for dilution and washed three times (75 ml each) with ether. The aqueous phase layer was acidified to pH=2 with 2N HCl aqueous solution and subsequently extracted with ethyl acetate three times (75 ml each). The organic phase layers were combined and concentrated to give 1.50 g of crude product. The crude product was recrystallized by a solvent mixture of ethyl acetate and hexane (1:2, 30 ml, v/v) and filtered under reduced pressure to obtain a white solid, Fmoc-β-Ala. yield: 1.41 g (81%). NMR (CDCl3) δ 2.6 (t, 2H, NHCH2CH2COOH), 3.47 (d, 2H, J = 7.0 Hz, NHCH2CH2COOH), 4.19 (t, 1H, J = 6.0 Hz, Fmoc-CH), 4.39 (d, 2H, J = 7.0 Hz, Fmoc-CH2), 7.29 (t, 2H , J = 7.3 Hz, Ar-H), 7.38 (t, 2H, J = 7.3 Hz, Ar-H), 7.56 (d, 2H, J = 7.0 Hz, Ar-H), 7.74 (d, 2H, J = 7.5 Hz, Ar-H).
