(E-2-13C)-Non-2-enoic acid

The colourless solution was warmed to room temperature and stirred overnight. The solvent was removed in vacuo and the residue extracted with Et2O (3 × 2 mL) and petroleum ether (3 × 2 mL).

The combined organics were evaporated to give a yellow oil (104 mg). Column chromatography (petroleum ether : EtOAc 4 : 1 to 1 : 2) gave (E-2-13C)-5 (10 mg, 0.064 mmol, 14%, 96% 13C-2, 4% 13C-1 atom) and (Z-2-13C)-5 10 mg, 0.064 mmol, 14%, 96% 13C-2, 4% 13C-1 atom) as colourless oils [the 13C content at the 1- and 2-positions were deduced by inspection of their 1H NMR and 13C NMR spectra (see ESI p44-45)]. (E-2-13C)-5: Rf 0.14 (petroleum ether : EtOAc 6 : 1); IR (neat) 3300-2800, 1692, 1627 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.06 (ddt, J = 15.6, 7.0, 1.8 Hz, 1H, β-H), 5.78 (ddt, 1JCH = 163, J = 15.6, 1.5 Hz, 1H, -H), 2.21 (ddq, J = 6.8, 6.0, 1.5 Hz, 2H, CH2CH=13CH), 1.48 – 1.40 (m, 2H, CH2), 1.32 – 1.22 (m, 6H, 3 × CH2), 0.87 (t, J = 7.0 Hz, 3H, CH3); 13C NMR (101 MHz, CDCl3) δ 170.8 (d, J = 74.2 Hz, CO2H), 152.4 (d, 1JCC = 69.7 Hz, β-C), 120.3 (-13C), 32.3 (CH2), 31.6 (CH2), 28.8 (CH2), 27.8 (CH2), 22.5 (CH2), 14.1 (CH3); MS (CI+, NH3) m/z 175 (M + NH4)+; HRMS (CI+, NH3) m/z calcd for C8(13C)H22NO2 (M + NH4)+ 175.1527, found 175.1527.