Reaction Steps
To a cooled (−78° C.) solution of tert-butyl N-[ethoxy(oxo)acetyl]-N-methylglycinate (1.43 g, 5.85 mmol) and 1-(4-fluorobenzyl)-5,6-dihydropyridin-2(1H)-one from Step 3 of Example 1 (1 g, 5 mmol) in anhydrous THF (10 mL) was added LiHMDS (1 M in THF) (1.02 g, 6.09 mmol) dropwise. The reaction mixture was stirred for 10 min. at −78° C., warmed to room temperature for 2.5 hours, then heated to 40° C. After heating for 24 hours, the reaction mixture was quenched with cold diluted HCl, then diluted with methanol, and concentrated under vacuum. The residual material was purified using reverse phase HPLC on a C18 stationary phase eluting with 5%-95% acetonitrile (0.1% TFA) in H2O (0.1% TFA) to give the title compound as a mixture of diastereomers. The appropriate fractions were collected for the first-eluting diastereomer, diastereomer 1, and this material was purified further using reverse phase HPLC on a C18 stationary phase eluting with 15%-85% acetonitrile (0.1% TFA) in H2O (0.1% TFA). For the second eluting diastereomer, diastereomer 2, the appropriate fractions were collected and the material was purified further using reverse phase HPLC on a C18 stationary phase eluting with 10%-60% methanol (0.1% TFA) in H2O (0.1% TFA). Diastercomer 1, the hydrogens at positions 4a and 5 have a trans relationship to one another: 1H NMR (400 MHz, CDCl3) δ 6.84 (m, 2H), 6.62 (t, J=8.7 Hz, 2H), 4.31 (d, J=14.7 Hz, 1H), 4.05 (d, J=14.7 Hz, 1H), 3.43 (d, J=6.5 Hz, 1H), 2.91 (m, 2H), 2.69 (m, 1H), 2.57 (s, 3H), 1.42 (m, 1H), 1.21 (m, 1H), 1.15 (s, 9H) ppm. ES MS M+1=405. Diastereomer 2, the hydrogens at positions 4a and 5 have a cis relationship to one another: 1H NMR (400 MHz, CDCl3) δ 13.07 (s, 1H), 7.22 (m, 2H), 7.02 (t, J=8.7 Hz, 2H), 4.67 (d, J=14.7 Hz, 1H), 4.51 (d, J=14.7 Hz, 1H), 3.82 (d, J=6.5 Hz, 1H), 3.33 (m, 1H), 2.99 (s, 3H), 2.02 (m, 3H), 1.68 (m, 1H), 1.44 (s, 9H) ppm. ES MS M+1=405.
