Reaction Steps
A solution of (±)-ethyl (3-hydroxycyclopentenyl)butylphosphinate (7) (3.66 g, 15.8 mmol) in anhydrous DMF (100 cm3) was treated with t-butyldimethylsilyl chloride (2.62 g, 17.4 mmol), triethylamine (4.55 cm3) and DMAP (425 mg). The reaction mixture was stirred at room temperature for 16 h, after which time the solvent was removed in vacuo. The residue was partitioned between DCM (50 cm3) and water (30 cm3) and the aqueous layer was further extracted with DCM (3×20 cm3). The combined organic layers were washed with water (2×30 cm3) and brine (40 cm3), dried over anhydrous sodium sulfate, filtered and the solvent removed under reduced pressure. The crude product was purified by short column vacuum chromatography on silica gel (15% ethanol/ethyl acetate) to yield the desired title compound (8) as a colourless oil (3.35 g, 61%): 1H-NMR (300 MHz, CDCl3) δH 0.09 (6H, s, Si(CH3)2), 0.89 (9H, s, SiC(CH3)3), 0.91 and 0.93 (3H, 2×d, J=7.2 and 7.2 Hz, PCH2CH2CH2CH3), 1.22-1.83 (9H, m, POCH2CH3, PCH2CH2CH2CH3, PCH2CH2CH2CH3, PCH2CH2CH2CH3), 2.26-2.72 (4H, m, C(4)—H, C(4)—H′, C(5)—H and C(5)—H′), 3.84-4.19 (2H, m, POCH2CH3), 4.97 (1H, m, C(3)—H), 6.50 and 6.54 (1H, 2×d, J=9.6 and 9.6 Hz, C(2)—H); 13C-NMR (75 MHz, CDCl3) δC −4.81 and −4.74 (d, 6JPC=5.7 Hz, Si(CH3)2), 13.48 (s, PCH2CH2CH2CH3), 16.43 and 16.51 (d, 6JPC=6.23 Hz, SiC(CH3)3), 18.08 (s, POCH2CH3), 23.43 (t, 2JPC=3.15 and 3.15 Hz, PCH2CH2CH2CH3), 23.69 and 23.90 (d, 3JPC=15.90 Hz, PCH2CH2CH2CH3), 25.75 (s, SiC(CH3)3), 27.22 and 28.54 (2×d, JPC=99.6 and 99.0 Hz, PCH2CH2CH2CH3), 31.55 and 31.70 (2×d, 3JPC=11.63 and 11.63 Hz, C(4)), 34.54 (t, 2JPC=8.25 and 8.55 Hz, C(5)), 60.15 (2×d, 2JPOC=6.30 and 6.83 Hz, POCH2CH3), 77.97 and 78.22 (d, 3JPC=18.45 Hz, C(3)), 136.64 and 138.24 (2×d, JPC=119.78 and 120.08 Hz, C(1)), 148.51 (d, 2JPC=9.38 Hz, C(2)); 31P-NMR (121 MHz, CDCl3) δP 42.77 and 43.15; MS (CI, CH4) m/z 347.2 (16%) (MH+), 215.1 (100), 375.3 (44), 289.2 (39). Synthesis of (±)-cis-ethyl [3(t-butyldimethylsilyloxy)cyclopentanyl]butylphosphinate (9)
