3.8.1. Synthesis of (S)-2-methyloctanoic Acid

To a solution of trimethylaluminum (891 μL, 1.782 mmol) and (+)-(NMI)2ZrCl2 (23.84 mg, 0.036 mmol) in 1.5 mL of CH2Cl2 was added a solution of oct-1-ene (100 mg, 0.891 mmol) in 1.5 mL of CH2Cl2. After stirring overnight at 23 ◦C, the mixture was treated with a vigorous stream of O2 for 1 h at 0 ◦C and then stirred for 5 h under an atmosphere of O2 at room temperature. The reaction mixture was quenched with 1 M HCl, extracted with CH2Cl2, washed with brine, dried over MgSO4 and concentrated. The residue was purified via silica flash column chromatography (20% ethyl acetate/hexanes) to yield (*S*)-2-methyloctan-1-ol (50 mg, 0.347 mmol, 39% yield) as a clear oil. The crude product was used in the next step without further purification.

To a solution of (*S*)-2-methyloctan-1-ol (50 mg, 0.347 mmol) in acetonitrile (1.4 mL) was added *N*-methyl morpholine *N*-oxide (NMO) solution in H2O (468 mg, 3.47 mmol) and tetrapropylammonium perruthenate (TPAP) (12.18 mg, 0.035 mmol) sequentially at room temperature and the mixture was stirred for 2 h. The mixture was then concentrated, and the residue passed through a pad of silica gel using hexanes:diethyl ether (3:1) containing 0.1% acetic acid. The eluted solvent was concentrated to yield (*S*)-2-methyloctanoic acid (48 mg, 0.303 mmol, 88% yield). [α] 26 <sup>D</sup> +10.0 (c 1.05, MeOH); 1H NMR (500 MHz, CDCl3) δ 2.46 (ddq, J = 9.7, 6.8, 3.1 Hz, 1H), 1.69 (m, 2H), 1.44 (m, 2H), 1.37–1.24 (m, 6H), 1.19 (m, 3H), 0.89 (m, 3H); 13C NMR (126 MHz, CDCl3) δ 183.2, 39.6, 33.7, 31.9, 29.4, 27.3, 22.8, 17.1, 14.3. HRESIMS *m*/*z* [M + H]<sup>+</sup> 159.1394 (calc. for C9H19O2, 159.1385).
