[CH2:1]([O:8][C@@H:9]1[CH2:13][C@H:12]([OH:14])[CH:11]=[CH:10]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C(N(CC)CC)C.[C:22]([O:25][CH:26]=[CH2:27])(=[O:24])[CH3:23].C(Cl)(Cl)Cl>COC(C)(C)C>[CH2:1]([O:8][C@@H:9]1[CH2:13][C@H:12]([OH:14])[CH:11]=[CH:10]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[CH2:1]([O:8][C@@H:9]1[CH2:13][C@H:26]([O:25][C:22](=[O:24])[CH3:23])[CH:27]=[CH:10]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1Cis-4-benzyloxy-cyclopent-2-enol (500 mg, prepared in example 16) is dissolved in tert-butyl methyl ether (8.6 mL, anhydrous). To the solution is added triethylamine (0.7 eq), pancreatin (3 wt eq, available from Sigma Chemical Company), and vinyl acetate (5 eq). The reaction is allowed to stir for 7 hours at room temperature. The reaction is then filtered through diatomaceous earth and the filtrate is concentrated under vacuum. The products are separated by chromatography on silica gel (20% ethyl acetate/hexane) to provide (-)-cis-4-benzyloxy-cyclopent-2-enol (A) (147 mg, 29% yield) [α]20D -12°, (c=1.09, chloroform), and (-)-acetic acid cis-4-benzyloxy-cyclopent-2-enyl ester (B) (427 mg, 70% yield),[α]20D =-5.2°, (c=0.97, chloroform), 1 H NMR (CDCl3) δ 7.3 (m, 5H), 6.13 (d, 1H, J=5 Hz), 5.99 (d, 1H, J=5 Hz), 5.5 (m, 1H), 4.59 (d, 1H, J=11.8 Hz), 4.54 (d, 1H, J=11.8 Hz), 4.5 (m, 1H), 2.78 (d appt, 1H, J=7.2, 14.3 Hz), 2.05 (s, 3H), 1.76 (d appt, 1H, J=4.4, 14.3 Hz); 13C NMR (CDCl3) δ171.1, 138.5, 136.4, 133.1, 128.7, 128, 127.9, 81.4, 77.1, 71.2, 37.8, 21.4.
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