[CH2:1]([C@H:8]1[C:12]([CH3:14])([CH3:13])[O:11][C:10](=[O:15])[NH:9]1)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.C([Li])CCC.[C:21](Cl)(=[O:26])[C:22]([CH3:25])([CH3:24])[CH3:23].C(OCC)(=O)C>O1CCCC1>[CH3:23][C:22]([CH3:25])([CH3:24])[C:21]([N:9]1[C@@H:8]([CH2:1][C:2]2[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=2)[C:12]([CH3:13])([CH3:14])[O:11][C:10]1=[O:15])=[O:26]Reaction of the auxiliary (10) (0.085 g, 0.415 mmol) in solution in tetrahydrofuran (2 ml) at -78° C. with butyllithium (1.6M, 0.262 ml, 0.419 mmol) and pivaloyl chloride (0.056 ml, 0.456 mmol) for 30 minutes and then at room temperature for 2 hours with work-up and flash column chromatography using 30% ethyl acetate/40-60 petroleum ether furnished the title compound (19) as an oil (0.104 g, 87%); νmax (CDCl3) 1742 cm-1 ; δH (CDCl3 ; 300 MHz) 1.30 (3H, s, C(CH3)2), 1.34 (6H, s, C(CH3)3), 1.35 (3H, s, C(CH3)2), 2.86 (1H, dd, J=9.3 and 14.2, CH2Ph), 3.05 (1H, dd, J=4.1 and 14.2, CH2Ph), 4.53 (1H, dd, J=4.2 and 9.3, CHCH2), 7.18-7.28 (5H, m, ArCH); δC (125 MHz; CDCl3) 22.10 (CH3), 26.29 (CH3), 28.07 (CH3), 35.24 (CH2), 41.68 (C), 65.47 (CH), 81.80 (C), 126.94 (CH), 128.76 (CH), 129.38 (CH), 137.19 (C), 152.03 (CO), 179.49 (CO); m/z (CI+, NH3) 290 (M+ +1).
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