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Procedure for the Preparation of Esters 9a and 11c: To a solution of the acid (3 mmol) in CH2Cl2 (10 mL) were successively added DMAP (0.122 g, 1 mmol) and 1,4-pentadien-3-ol (0.252 g, 3 mmol). The reaction mixture was cooled to 0 °C and a solution of dicyclohexylcarbodiimide (0.618 g, 3 mmol) in CH2Cl2 (1.5 mL) was added dropwise. After stirring for 5 min at 0 °C, the cooling bath was removed and the mixture stirred overnight at r.t. Urea was filtered off and the solvent removed by evaporation under reduced pressure. Purification of the crude product by flash-chromatography on silica (Eluent: EtOAc-hexanes 10:90) afforded the corresponding ester.
18 Spectroscopic data for 9a: 1H NMR (CDCl3): δ = 0.89 (t, J = 7.1 Hz, 3 H), 1.23 (m, 4 H), 2.03 (q, J = 6.2 Hz, 2 H), 3.06 (d, J = 5.6 Hz, 2 H), 5.23 (dt, J = 10.4, 1.1 Hz, 2 H), 5.30 (dt, J = 17.1, 1.1 Hz, 2 H), 5.55 (m, 2 H), 5.71 (tt, J = 6.0, 0.9 Hz, 1 H), 5.83 (ddd, J = 17.1, 10.4, 6.0 Hz, 2 H). 13C NMR (CDCl3): δ = 13.6, 21.9, 31.1, 31.9, 37.9, 74.4, 116.8, 121.6, 134.2, 135.1, 169.9 (C=O). HRMS: m/z calcd for [C13H20O2 + H+] = 208.1463. Found: 208.1463. Compound 11c: 1H NMR (CDCl3): δ = 0.88 (t, J = 7.0 Hz, 3 H), 1.25-1.52 (m, 8 H), 2.20 (qd, J = 7.0, 1.2 Hz, 2 H), 5.24 (dt, J = 10.4, 1.2 Hz, 2 H), 5.32 (dt, J = 16.9, 1.2 Hz, 2 H), 5.76 (tt, J = 5.9, 1.0 Hz, 1 H), 5.80-5.93 (m, 3 H), 7.00 (dt, J = 15.6, 7.0 Hz, 1 H). 13C NMR (CDCl3): δ = 13.9, 22.4, 27.9, 28.7, 31.5, 32.1, 74.3, 116.9, 121.2, 135.2, 149.4, 164.9 (C=O). HRMS: m/z calcd for [C14H22O2 +H+] = 222.1619. Found: 222.1619. Compound 14: Same procedure as above by using 1,5-hexadien-3-ol (0.288 g, 3 mmol) instead of 1,4-pentadien-3-ol. 1H NMR (CDCl3): δ = 0.88 (t, J = 6.6 Hz, 3 H), 1.21-1.50 (m, 8 H), 2.18 (q, J = 7.0 Hz, 2 H), 2.42 (t, J = 6.8 Hz, 2 H), 5.02-5.13 (m, 2 H), 5.18 (dt, J = 10.5, 1.3 Hz, 1 H), 5.26 (dt, J = 17.3, 1.3 Hz, 1 H), 5.37 (q, J = 6.3 Hz, 1 H), 5.68-5.88 (m, 3 H), 6.97 (dt, J = 15.6, 7.0 Hz, 1 H). 13C NMR (CDCl3): δ = 14.0, 22.6, 28.0, 28.9, 31.7, 32.2, 38.9, 73.3, 116.5, 117.8, 121.3, 133.2, 136.1, 149.5, 165.6.
19 Photodeconjugation of ester 11c: To a solution of ester 11c (10 mmol) in CH2Cl2 (100 mL) was added N,N-dimethyl-ethanolamine (30 mmol). The resulting solution was first deoxygenated by a stream of nitrogen for 10 min and was then poured into 12 mm diameter quartz tubes which were fitted by septa and placed around a transparent quartz Dewar in which a short wave length OSRAM lamp (λ = 254 nm) was disposed. The irradiation was carried out at 0 °C. After total disappearance of the starting material (thin-layer chromatography control), the solvent was removed by concentration. The deconjugated ester was purified by flash-chromatography (Eluent EtOAc-petrol ether 5:95). Compound 9c: 1H NMR (CDCl3): δ = E-isomer: 0.86 (t, J = 6.7 Hz, 3 H), 1.21-1.40 (m, 6 H), 2.04 (q, J = 6.3 Hz, 2 H), 3.06 (d, J = 5.6 Hz, 2 H), 5.23 (d, J = 10.4 Hz, 2 H), 5.30 (dt, J = 17.1, 1.1 Hz, 2 H), 5.56 (m, 2 H), 5.72 (tt, J = 6.0, 1.1 Hz, 1 H), 5.84 (ddd, J = 17.1, 10.4, 6.0 Hz, 2 H). Z-isomer: 0.86 (t, J = 6.7 Hz, 3 H), 1.21-1.40 (m, 6 H), 2.04 (q, J = 6.3 Hz, 2 H), 3.14 (d, J = 5.6 Hz, 2 H), 5.23 (d, J = 10.4 Hz, 2 H), 5.30 (dt, J = 17.1, 1.1 Hz, 2 H), 5.56 (m, 2 H), 5.72 (tt, J = 6.0, 1.1 Hz, 1 H), 5.84 (ddd, J = 17.1, 10.4, 6.0 Hz, 2 H). 13C NMR (CDCl3): δ = E-isomer: 14.2, 22.7, 31.5, 31.7, 32.7, 38.4, 75.1, 117.4, 121.6, 133.7, 135.3, 170.9 (C=O). HRMS: m/z calcd for [C14H22O2 + H+] = 222.1619. Found: 222.1618.
20
Ring-Closing Metathesis/Rearrangement of Esters 9a, 9c, 11c or 14 - General Procedure: To a solution of the ester (1 mmol) in CH2Cl2 (100 mL) through which a stream of dried nitrogen had been passed, was added Grubbs type II catalyst (5%). The reaction mixture was heated to reflux for 4 h. After disappearance of the starting material, the reaction mixture was concentrated and purified by flash-chromatography on silica. Compound 6: 1H NMR (CDCl3): δ = 3.07 (s, 2 H), 5.25 (dt, J = 10.4, 1.2 Hz, 1 H), 5.34 (dt, J = 17.1, 1.2 Hz, 1 H), 5.41 (m, 1 H), 5.90 (m, 3 H). 13C NMR (CDCl3): δ = 30.3, 80.3, 117.9, 122.4, 125.4, 134.8, 169.8 (C=O). HRMS: m/z calcd for [C7H8O2 + H+] = 125.0602. Found: 125.0601. Compound 7a: 1H NMR (CDCl3): δ = 0.89 (t, J = 7.0 Hz, 3 H), 1.23-1.48 (m, 4 H), 2.06 (q, J = 6.5 Hz, 2 H), 3.03-3.10 (m, 2 H), 5.33 (s, 1H), 5.49 (ddt, J = 15.3, 7.1, 1.3 Hz, 1 H), 5.79 (dt, J = 15.3, 7.1 Hz, 1 H), 5.86 (s, 2 H). 13C NMR (CDCl3): δ = 14.1, 22.4, 30.2, 31.1, 32.0, 80.6, 121.7, 126.1, 134.2, 136.1, 169.6 (C=O). HRMS: m/z calcd for [C11H16O2 + H+] = 181.1228. Found: 181.1229. Compound 7c: 1H NMR (CDCl3): 0.90 (t, J = 6.8 Hz, 3 H), 1.24-1.43 (m, 6 H, H), 2.04 (q, J = 7.2 Hz, 2 H), 3.03-3.10 (m, 2 H), 5.31-5.39 (m, 1 H), 5.48 (ddt, J = 15.3, 7.2, 1.3 Hz, 1 H), 5.79 (dt, J = 15.3, 7.2 Hz, 1 H), 5.86 (s, 2 H). 13C NMR (CDCl3): δ = 14.3, 22.8, 28.7, 30.3, 31.6, 32.3, 80.6, 121.9, 126.2, 126.7, 136.0, 169.2 (C=O). HRMS: m/z calcd for [C12H18O2 + H+] = 265.2167. Found: 265.2166. Compound 12a:21 1H NMR (CDCl3): δ = 5.35 (d, J = 10.2 Hz, 1 H), 5.43 (s, 1 H), 5.48 (d, J = 17.0 Hz, 1 H), 5.72 (ddd, J = 17.0, 10.2, 6.9 Hz, 1 H), 6.17 (dd, J = 5.6, 2.1 Hz, 1 H), 7.43 (dd, J = 5.7, 1.4 Hz, 1 H). 13C NMR (CDCl3): δ = 84.0, 120.1, 121.6, 131.6, 155.3, 173.2 (C=O). 13c:22 1H NMR (CDCl3): δ = 0.90 (t, J = 6.7 Hz, 3 H), 1.23-1.40 (m, 8 H, H), 2.06 (q, J = 6.6 Hz, 2 H), 5.25 (ddt, J = 15.3, 7.7, 1.2 Hz, 1 H), 5.39 (d, J = 7.7 Hz, 1 H), 5.90 (dt, J = 15.3, 6.9 Hz, 1 H), 6.09 (dd, J = 5.6, 1.9 Hz, 1 H), 7.35 (dd, J = 5.6, 1.5 Hz, 1 H). 13C NMR (CDCl3): δ = 14.2, 22.7, 28.8, 28.9, 31.8, 32.4, 84.2, 121.4, 123.3, 138.3, 155.8, 173.3 (C=O). HRMS: m/z calcd for [C12H18O2 + H+] = 194.1307. Found: 194.1308. Compound 17: 1H NMR (CDCl3): δ = 0.87 (t, J = 6.6 Hz, 3 H), 1.21-1.39 (m, 8 H), 2.02 (q, J = 6.7 Hz, 2 H), 2.36-2.60 (m, 2 H), 5.04 (t, J = 6.4 Hz, 1 H), 5.37 (dt, J = 15.3, 7.7 Hz, 1 H), 5.60 (dt, J = 15.3, 7.5 Hz, 1 H), 6.13 (dd, J = 5.7, 2.1 Hz, 1 H), 7.46 (dd, J = 5.7, 1.4 Hz, 1 H). 13C NMR (CDCl3): δ = 14.4, 22.9, 29.1, 29.5, 32.0, 32.9, 36.6, 83.3, 122.2, 122.3, 136.5, 156.3, 173.3 (C=O). HRMS: m/z calcd for [C13H20O2 + H+] = 208.1463. Found: 208.1462. Compound 8: 1H NMR (CDCl3): δ = 0.88 (t, J = 6.7 Hz, 3 H), 1.20-1.40 (m, 8 H), 1.86-2.10 (m, 2 H), 2.32-2.54 (m, 2 H), 4.86 (q, J = 7.0 Hz, 1 H), 5.57 (dt, J = 15.1, 7.0 Hz, 1 H), 5.81 (dt, J = 15.1, 6.7 Hz, 1 H), 6.02 (dt, J = 9.8, 1.9 Hz, 1 H), 6.84 (dt, J = 9.8, 4.2 Hz, 1 H).
21
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