L-Lysine → (S)-2-Amino-6-benzamidohexanoic acid

Participants

Reaction Conditions

Reaction Steps

This compound was synthesized by a modified procedure of Kurtz et al.93. Copper (II) carbonate, basic (16.3 g, 74.0 mmoles) was added to a hot (80° C.) solution of L-lysine (15 g, 82.0 mmoles) in distilled water (250 mL). Excess copper carbonate was removed by gravity filtration while the mixture was still warm. The epsilon amino group of L-lysine was benzoylated by the dropwise addition of benzoyl chloride (14 g, 99.0 mmoles) in THF (35 mL) to the above solution after being cooled to 5° C. Sodium bicarbonate was added in small portions (total 14 g, 167.0 mmoles) to maintain the pH of the aqueous solution above 7 (pH was monitored with neutral litmus paper). The cold solution was maintained at 5° C. for 4 h and 2 d at room temperature. A hot (80° C.) solution (1 L) of EDTA (14.6 g, 0.25 moles) was added to the reaction mixture, stirred for 1 h and cooled to 10° C. The precipitate collected by vacuum filtration was washed with water and 30 mL of 95% ethanol. The powder, containing the product was purified by first adding the powder to 1×10-1M hydrochloric acid (300 mL) and filtering off the sediment. The filtrate was slowly neutralized with 0.01N sodium hydroxide and the precipitate collected by gravity filtration. The latter was then air-dried to give 13 g (57 mmoles) (69.5% yield) of a white powder, mp 232°-234° C. (lit.93 mp 230°-233° C.). 1H-NMR (DMSO-d6) δ 1.36-190(6Ha,m); 3.20(2Hb,m); 4.20-4.53(1Hc,m); 7.16(1Hd,m, rotamer of amide -NH); 7.43(2He,e', app. dd, Jef =8Hz, Jee,=2Hz); 7.63(1Hf, app. dd, Jfe =8Hz, Jfg =2Hz); 8.03(2Hf,f', app dd, Jge =8Hz, Jgf =2Hz); 9.50(1Hh,s)ppm. IR (Nujol) 3330, 3030, 1687, 1270, 735, 695 cm-1.

Provenance & Evidence