D-2-THIENYLALANINE

White to off-white crystals

STR174 (2R)-2-Amino-3-(2-thienyl)propionic acid (5.00 g, 29.2 mmol) was dissolved in formic acid (50 ml). The solution was cooled to 0 C. Acetic acid anhydride (20 ml) was added dropwise. The reaction mixture was stirred for 16 h, while it was warming up to room temperature. It was cooled to 0 C. Water (20 ml) was added dropwise. The solution was warmed to room temperature. The solvent was removed in vacuo. The residue was suspended in ethyl acetate (20 ml). The precipitation was filtered off, collected, and dried in vacuo, to give 3.60 g of crude (2R)-2-(formylamino)-3-(2-thienyl)propionic acid, which was used for the following step. 1 H-NMR (DMSO d, ): d 3.05 and 3.15 (both ABX, together 1H); 3.30 and 3.55 (m and ABX, together 1H); 4.30 and 4.55 (both m, together 1H); 6.90 (m, 1H); 6.95 (m, 1H); 7.35 (d, 1H); 8.03 (s, 1H); 8.40 (d, 1H); 12.92 (br, 1H).The salt thus obtained was added with 550 mL of acetone, refluxed for 4 hr, and then cooled to room temperature, after which the deposited 3-2-thienyl-D-alanine was obtained (LID ratio=4I96).