[CH:1]1([C:5]#[N:6])[CH2:4][CH2:3][CH2:2]1.C([N-]C(C)C)(C)C.[Li+].[O:15]1[CH2:19][CH2:18][C:17](=[O:20])[CH2:16]1.CN(C)P(N(C)C)(N(C)C)=O>C1COCC1>[OH:20][C:17]1([C:1]2([C:5]#[N:6])[CH2:4][CH2:3][CH2:2]2)[CH2:18][CH2:19][O:15][CH2:16]1
To a solution of cyclobutanecarbonitrile (405 mg, 5 mmol) in THF (7 ml) was added 2.0M lithium diisopropylamide (2.5 ml, 5 mmol) dropwise at −78° C. The reaction solution was stirred at −78° C. for 40 minutes, followed by the addition of a solution of dihydrofuran-3(2H)-one (473 mg, 5.5 mmol) in hexamethylphosphoramide (268 mg, 1.5 mmol). The mixture was warmed to room temperature and stirred for 3 hours. The reaction mixture was quenched with 1N aqueous HCl solution and extracted with EtOAc (3×20 mL). The combined organic phases were washed with brine (10 mL), dried over Na2SO4, filtered and concentrated. The residue was purified by column chromatography (eluted with petroleum ether:EtOAc=20:1) to provide the title compound as a corloless oil (0.37 g, yield 44%). 1H NMR (400 MHz, CDCl3): δ 4.15-4.05 (m, 2H), 3.86 (d, J=10.0 Hz, 1H), 3.74 (d, J=9.6 Hz, 1H), 2.47-2.42 (m, 4H), 2.39-2.31 (m, 3H), 2.01-1.94 (m, 2H).
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