1: 39 percent / N,N-dicyclohexylcarbodimide / dioxane / 15 h 2: 60 percent / AlCl3 / CH2Cl2 / 2 h / Ambient temperature View Scheme

diphenyl-phosphinic acid; sodium hydrogencarbonate in N,N-dimethyl-formamide T=0°C; 72 h;

Multi-step reaction with 4 steps 1.1: 97 percent / PyBrOP; diisopropylethylamine / dimethylformamide / 0 - 20 °C2.1: trifluoroacetic acid / 0.33 h / 20 °C2.2: 63 percent / diisopropylethylamine; 1-hydroxybenzotriazole; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride / CH2Cl2 / 24 h / 20 °C3.1: 82 percent / LiOH*H2O / tetrahydrofuran; methanol; H2O / 1 h / 20 °C4.1: HCl / ethyl acetate / 1 h