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

To a stirred solution of either (1-13C)-1-bromonona-1,2-diene [(1-13C)-4] (100 mg, 0.49 mmol) in acetone (2 mL) at -40 °C was added a 0.10 M solution of DMDO in acetone (3.20 mL, 0.320 mmol). 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.