N-Hydroxysuccinimide [Coupling Reagent for Peptide]

Experimental procedure: A mixture of 1 (3.8 g, 17.5 mmol) and N-hydroxysuccinimide (3.0 g, 26.2 mmol) in CH₂Cl₂ (100 mL) and THF (50 mL) at 0 °C is treated with EDC･HCl (5.0 g, 26.2 mmol), and the mixture is stirred at the same temperature for 12 h. The reaction is quenched with H₂O, and the mixture is partitioned between AcOEt and H₂O. The organic phase is washed with saturated aqueous NaCl, dried (Na₂SO₄), filtered, and concentrated in vacuo. The residue (2) in CH₂Cl₂ (100 mL) is treated with 3-amino-1-propanol (2.0 mL, 26.2 mmol) at 0 °C and stirred at room temperature for 8 h. The resulting mixture is partitioned between AcOEt and H₂O. The organic phase is washed with H₂O (twice), saturated aqueous NaCl, dried (Na₂SO₄), filtered, and concentrated in vacuo. The residue is purified by silica gel column chromatography (40% AcOEt－hexane) to afford 3 as a colorless syrup (4.0 g, 84% over two steps).