DL-3-(1-NAPHTHYL)ALANINE

b alpha-Amino-1-naphthalenepropanoic acid A solution of the product from part (a) (16.182 g., 47.5 mmol.) was suspended in 48% hydrogen bromide (100 ml.) and refluxed under argon for 14 hours. The hydrogen bromide salt of the product was filtered out of solution as a white solid, then taken up in hot (50) water (500 ml.) and the solution neutralized with concentrated ammonium hydroxide. The product precipitated out of solution as a fine white solid. Upon filtration and drying under high vacuum overnight (18 hours), 8.335 g. of product was obtained as a fluffy white solid; m.p. 264.b alpha-Amino-1-naphthalenepropanoic acid A solution of the product from part (a) (16.182 gm., 47.5 mmol) was suspended in 48% hydrogen bromide (100 ml) and refluxed under argon for 14 hours. The hydrogen bromide salt of the product was filtered out of solution as a white solid, then taken up in hot (50 C.) water (500 ml) and the solution neutralized with concentrated ammonium hydroxide. The product precipitated out of solution as a fine white solid. Upon filtration and drying under high vacuum overnight (18 hours), 8.335 g. of product was obtained as a fluffy white solid; m.p. 264 C.b alpha-Amino-1-naphthalenepropanoic acid A solution of the product from part (a) (16, 182 gm., 47.5 mmol) was suspended in 48% hydrogen bromide (100 ml) and refluxed under argon for 14 hours. The hydrogen bromide salt of the product was filtered out of solution as a white solid, then taken up in hot (50 C.) water (500 ml) and the solution neutralized with concentrated ammonium hydroxide. The product precipitated out of solution as a fine white solid. Upon filtration and drying under high vacuum overnight (18 hours), 8.335 g. of product was obtained as a fluffy white solid; m.p. 264 C.To a flask containing DL-1-Naphthylalanine (1a) (1.0 g, 4.6 mmol), TMSCl (1.51 g, 14 mmol, 3 eq) was added, followed by anhydrous methanol (10 mL). The reaction was allowed to stir at room temperature overnight. Upon completion, the volatiles were removed in vacuo, affording the crude methyl ester hydrochloride (1.34 g). The crude salt was then dissolved in ethyl ether:methanol (7.5:1; 30 mL:4 mL) and cooled to -10 C. Triethylamine (6 mL) was slowly added and the reaction was stirred for one hour at -10 C. After reaction completion, the solution was filtered through a pad of celite to remove Et3N salt, and the filtrate was evaporated in vacuo affording the free base methyl ester (1.14 g). The methyl ester was dissolved in methanol (35 mL) and placed on an ice bath. Sodium borohydride (10 eq) was added portion-wise over 20 min and the reaction was allowed to come to room temperature overnight. The solvent was then evaporated, diluted with H2O (80 mL), and extracted with EtOAc (3 × 100 mL). The combined organic layers were dried over MgSO4, filtrated and concentrated in vacuo affording 2a as a white powder (0.87 g, 94%), which was used without further purification. 1H NMR (400 MHz, CDCl3T) delta8.05 (d, J = 7.0 Hz, 1H), 7.88 (d, J = 9.1 Hz, 1H), 7.77 (d, J = 8.7 Hz, 1H), 7.53 (sext, J = 7.6 Hz, 2H), 7.43 (t, J = 7.7 Hz, 1H), 7.36 (d, J = 6.2 Hz, 1H), 3.72 (dd, J = 3.7, 10.6 Hz, 1H), 3.49 (dd, J = 6.6, 10.6 Hz, 1H), 3.33 (m, 2H), 2.95 (dd, J = 9.7, 14.8 Hz, 1H). HRMS m/zcalculated for C13H16NO [M+H]+: 202.1232. Found: 202.1227.