Example 11
A 50° C. solution of L,L-lysyllysine (55.7 mg, 0.203 mmol) in methanol (0.5 mL) was treated with a solution of tocopherol (1.8 mg in 0.2 mL of EtOAc) and a solution of PDX (80.0 mg, 0.222 mmol) in methanol (0.5 mL). The solution stirred for 20 minutes, cooled slightly, and was concentrated in vacuo. The foam was re-suspended in HPLC grade acetonitrile (˜3 mL), stirred for 3 hours to triturate the solid, filtered, and dried overnight in the vacuum oven (ambient temperature) to afford 52 mg (39%) of PDX L,L-lysyllysine salt as a very sticky, orange solid. 1H NMR (400 MHz, Methanol-d4) δ 6.70 (dd, J=14.6, 9.3 Hz, 2H), 6.01-5.89 (m, 2H), 5.71 (ddd, J=14.8, 8.0, 6.4 Hz, 2H), 5.51-5.25 (m, 6H), 4.24 (dd, J=7.7, 5.3 Hz, 1H), 4.14 (m, 2H), 3.38 (t, J=6.5 Hz, 1H), 2.89 (t, J=7.3 Hz, 4H), 2.82 (t, J=6.4 Hz, 2H), 2.40-2.21 (m, 6H), 2.21-2.13 (m, 2H), 2.04 (m, 2H), 1.91-1.78 (m, 2H), 1.66 (m, 6H), 1.45 (m, 4H), 0.94 (t, J=7.5 Hz, 3H).
