Ethyl 1-(4-iodobutyl)-1-cyclobutanecarboxylate → Ethyl 11-[1-(ethoxycarbonyl)cyclobutyl]-2,2-dimethyl-7-oxoundecanoate

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Compound 106e was prepared likewise Method C starting from 108a (11.01 g, 30.1 mmol), 105b (10.28 g, 33.1 mmol) and KOtBu (4.06 g, 36.2 mmol) to give, after purification by column chromatography (silica, heptane:EtOAc=6:1; a layer of NaHCO3 was put on the base of the column), ethyl 1-[11-ethoxy-5-isocyano-10,10-dimethyl-5-[(4-methylphenyl)sulfonyl]-11-oxoundecyl]-1-cyclobutanecarboxylate (14.11 g) as a colorless oil. Part of this oil (13.86 g, 25.3 mmol) was treated with cone aqueous HCl (50 mL), as described for 106d, to give crude 106e, which was stirred up in heptane (50 mL) and the resulting precipitate was filtered off and washed with heptane (3×50 mL). The combined filtrates were washed with aqueous NaOH (1M, 2×50 mL) and brine (50 mL) and dried to give 106e (9.44 g, >90% pure by 1H NMR, 75%) as a slightly yellow oil. 1H NMR: δ 4.12 (q, J=7.1 Hz, 2H), 4.09 (q, J=7.1 Hz, 2H), 2.50-2.29 (m, 2H), 2.37 (t, J=7.4 Hz, 4H), 1.95-1.70 (m, 6H), 1.61-1.44 (m, 6H), 1.30-1.09 (m, 4H), 1.25 (t, J=7.1 Hz, 3H), 1.24 (t, J=7.1 Hz, 3H), 1.14 (s, 6H). 13C NMR: δ 210.1, 177.3, 176.6, 60.1 (2×), 47.5, 42.57 (2×), 42.1, 40.4, 37.8, 30.0 (2×), 25.2 (2×), 24.7, 24.6, 24.2, 24.1, 15.7, 14.4, 14.3.

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