Naphthalene-2-sulfonyl chloride (18.18 g, 80.2 mmol) and NaOH (60 mL, 2 N) were added portion-wise over 1 h to a mixture of (R)-3-amino-3-phenyl-propionic acid HCl salt (14.70 g, 72.9 mmol) and N-methylmorpholine (4.0 mL, 36.5 mmol) in dioxane (250 mL). The pH was maintained at pH 11 with the 2N NaOH solution during the addition. After stirring for an additional 3 h, the mixture was diluted with CH2Cl2 (1 L), acidified, washed with water, dried over MgSO4, filtered, and concentrated in vacuo. Crystallization from CH2Cl2/hexane furnished the title compound. MS (-ESI, m/z) 354 (M−H)−.
