Reaction Steps
A solution of alcohol 14 (650 mg, 1.5 mmol) in CH2Cl2 (5 mL) was treated with (2S)-1-(1,2-dioxo-3,3-dimethylpentyl)-2-piperidinecarboxylic acid (23, 382 mg, 1.5 mmol, followed by 1,3-dicyclohexylcarbodiinide (370 mg, 1.8 mmol), and 4-(dimethylamino)-pyridine (128 mg, 1.0 mmol) under a nitrogen atmosphere. The resulting bright yellow suspension was allowed to stir overnight. The mixture was then filtered through glass wool and chromatographed (silica gel, 20-30% EtOAc/hexanes) to give (1R)-3-(3,4,5-trimethoxyphenyl)-1-[3-(tert-butoxycarbonylmethoxy)phenyl]-1-propyl (2S)-1-(3,3-dimethyl-1,2-dioxopentyl)-2-piperidinecarboxylate (776 mg, 78%) as a colorless oil: 1H NMR (CDCl3, 300 MHz) (single diastereomer, mixture of rotamers) 7.30-6.80 (m, 4H), 6.37 (s, 2H), 5.82 (t, J=6.1 Hz, 1H), 5.33 (d, J=5.2 Hz, 1H), 4.54 (s, 2H), 3.85 (s, 6H), 3.83 (s, 3H), 3.38 (d, J=12.6 Hz, 1H), 3.16 (td, J=12.8, 3.1 Hz, 1H), 2.60 (m, 2H), 2.45-2.05 (m, 3H), 1.70 (m, 6H), 1.50 (s, 9H), 1.45 (m, 2H), 1.25 (s, 3H), 1.23 (s, 3H), 0.90 (t, J=7.4 Hz, 3H); 13C NMR (CDCl3, 75MHz) (single diastereomer, mixture of rotamers) 208.2, 175.1, 170.1, 168.2, 167.6, 158.5, 153.6, 141.7, 137.0, 130.1, 120.9, 120.2, 114.6, 113.7, 105.7, 82.7, 66.2, 61.2, 56.5, 51.7, 47.1, 44.6, 38.2, 32.9, 32.4, 28.4, 26.8, 25.3, 23.9, 23.5, 21.6, 9.1.
