“…ppm. ESI-MSMS m/z (ES þ ) 369.24 [(Mþ1) þ , 14.9], 337.02 [ 93.00], 318.94 [100], 308.93 [45.7], 290.Est-65) was obtained as a yellow solid from isoleucine methyl ester and L-tartaric acid derivative, as reported[20,21]. 1 H NMR (400 MHz, CDCl 3 ) d 5.93 (d, J ¼ 1.9 Hz, 1H), 4.95 (s, 1H), 4.88 (d, J ¼ 10.7 Hz, 1H), 4.70 (s, 1H), 3.79 (s, 3H), 3.71 (s, 3H), 3.52 (d, J ¼ 12.2 Hz, 1H), 3.37 (dd, J ¼ 12.2, 2.4 Hz, 1H), 1.97e1.89 (m, 1H), 1.45e1.35 (m, 1H), 1.11e1.02 (m, 1H), 0.95e0.88 (m, 6H) ppm.…”