Sodium hydride (60% dispersion in oil, 400 mg (240 mg NaH, 10 mmol)) was washed with pentane (2×7 mL), and tetrahydrofuran (10 mL) was added. The product from Example 11, 4-((alpha-R)-alpha-((2S,5R)-2,5-dimethyl-4-(4-fluorobenzyl)-1-piperazinyl)-3-hydroxybenzyl)-N,N-diethylbenzamide (1.007 g, 2.0 mmol) was dissolved in the stirred suspension, and when effervescence had subsided, methyl iodide (249 μL, 568 mg, 4 mmol) was added. The reaction mixture was sealed under nitrogen and stirred for 6 h at ambient temperature. The reaction mixture was evaporated to dryness, and the residue was partitioned between ethyl acetate (15 mL) and water (5 mL). The organic layer was separated, the aqueous portion extracted with ethyl acetate (2×10 mL) and the combined organic extracts were dried over anhydrous sodium sulfate. The organic solution was evaporated to a pale yellow gum, which on trituration and sonication with pentane yielded 4-((alpha-R)-alpha-((2S,5R)-2,5-dimethyl-4-(4-fluorobenzyl)-1-piperazinyl)-3-methoxybenzyl)-N,N-diethylbenzamide as a flocculent white solid (0.798 g, 77% after drying at room temperature and 5 mm Hg). Calc. for C32H40FN3O20.25H2O: C, 73.60; H, 7.82; N, 8.05; F, 3.64. Found C, 73.58; H, 7.70; N, 8.04; F, 3.84%. 1H NMR (CDCl3, 300 MHz); δ 1.09 (d, J=6.2 Hz, 6H, superimposed on br m, 3H); 1.21 (br m, 3H); 1.99 (m, 2H); 2.57 (br m, 2H); 2.66 (m, 3H); 3.15 (d, J=13.3 Hz, 1H); 3.27 (br m, 2H); 3.54 (br m, 2H); 3.78 (s, 3H); 3.84 (d, J=13 Hz, 1H); 5.10 (s, 1H); 6.76 (s, 1H); 6.70 (d, J=8.1 Hz, 2H); 6.96 (t, J=8.2 Hz, 2H); 7.26 (m, 5H); 7.46 (d, J=7.8 Hz, 2H).
