Compound 2n

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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

Prepared according to general procedure 2 outlined for compound 2a from methyl 2,2-di(but-3-en-1-yl)-5-methyl-3-oxohex-5-enoate 1n (35.4 mg, 0.134 mmol). After a reaction time of 24 h at −25 °C, the crude product was purified by careful column chromatography (hexane/EtOAc 97:3 to 95:5 to elute the product, then 80:20 to elute ligand 3f) to afford diastereopure 2n as a colorless oil (20.7 mg, 58%, er: 82:18). ¹H NMR (400 MHz, CDCl₃) δ 5.77 (ddt, 1 H, J = 17.1, 10.2, 6.5 Hz, CH=CH₂), 5.00 (d, 1 H, J = 17.1 Hz, CH=CH_{c i s}H_trans), 4.93 (d, 1 H, J = 10.2 Hz, CH=CH_cisH_{t r a n s}), 3.91 (d, 1 H, J = 1.4 Hz, OH), 3.72 (s, 3 H, CO₂CH₃), 2.51 (qd, 1 H, J = 8.7, 3.7 Hz, CHCOH), 2.27–2.16 (m, 1 H, CH₂CH_aH_bCH=CH₂), 2.07–1.81 (m, 4 H, CH₂CH_aH_bCCO₂CH₃ + (CH₃)₂CCH_aH_bCH + CH₂CH_aH_bCH=CH₂ + CH_aH_bCH₂CCO₂CH₃), 1.81–1.70 (m, 2 H, CH₂CH₂CH=CH₂), 1.70–1.63 (m, 1 H, CCH₂H_aH_bCCO₂CH₃), 1.65 (d, 1 H, J = 13.8 Hz, (CH₃)₂CCH_aH_bCOH), 1.57 (d, 1 H, J = 13.8 Hz, (CH₃)₂CCH_aH_bCOH), 1.19 (s, 3 H, (CH₃)_a(CH₃)_bC), 1.19–1.10 (m, 1 H, CH_aH_bCH₂CCO₂CH₃), 1.09–1.03 (m, 1 H, (CH₃)₂CCH_aH_bCH), 1.06 (s, 3 H, (CH₃)_a(CH₃)_bC); ¹³C NMR (100 MHz, CDCl₃) δ 177.9 (CO₂CH₃), 138.5 (CH=CH₂), 114.4 (CH=CH₂), 94.3 (COH), 59.3 (CCO₂CH₃), 51.9 (2 C: CO₂CH₃ + CHCOH), 50.2 (CH₂COH), 50.1 ((CH₃)₂CCH₂CH), 40.5 ((CH₃)₂C), 34.4 (CH₂CH₂CCO₂CH₃), 33.0 (CH₂CH₂CH=CH₂), 30.8 ((CH₃)_a(CH₃)_bC), 30.1 (CH₂CH=CH₂), 29.4 (CH₂CH₂CCO₂CH₃), 28.5 ((CH₃)_a(CH₃)_bC); IR v_max (neat/cm^-1): 3505, 2949, 2865, 1705, 1641, 1459, 1433, 1382, 1365, 1327, 1270, 1253, 1198, 1156, 1065, 1045, 1013, 993, 910, 856, 824, 773, 737, 704; HRMS (ESI) calcd for C₁₆H₂₆O₃Na, [M+Na]⁺: 289.1774, found 289.1763. [α]²²_D = +32.2 (c = 0.33, CH₂Cl₂).

Enantiomeric purity of the product was determined by GC analysis (ChiraSil^® DEX CB 25m x 0.25mm column, isothermal run at 95 °C, flow rate = 1.0 mL/min, retention time: 347.8 min (minor), 353.5 min (major); er: 82:18.