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Part D: To a solution of 7-benzyl-4-(pyridin-2-yl)-5,6,7,8-tetrahydropyrido[3,4-d]pyrimidine (2.15 g, 7.1 mmol) and N,N-diisopropylethylamine (2.48 mL, 14.2 mmol) in dichloromethane (30 mL) at 0° C. was added 1-chloroethyl chloroformate (1.15 mL, 10.7 mmol) over several minutes. The resulting solution was stirred at 0° C. for 1.0 h and then at 25° C. for 20 h. To this solution was added a saturated aqueous sodium bicarbonate solution (50 mL), and the resulting two-phase mixture was stirred at 25° C. for 1.0 h. The phases were separated, and the aqueous phase was washed with dichloromethane. The combined organic phases were dried over anhyd. sodium sulfate, filtered, and concentrated. The residue was dissolved in methanol, and the solution was heated at reflux for 1.0 h. After cooling to room temperature the mixture was concentrated under vacuum. The residue was triturated with ethyl acetate, and the resulting solids were recovered by filtration and dried under vacuum to provide a purple solid. These solids were dissolved in a mixture of concentrated aqueous sodium carbonate solution and chloroform. The phases were separated, and the aqueous phase was washed twice with chloroform. The combined organic phases were washed with brine, dried over anhyd. sodium sulfate, filtered, and concentrated. The residue was maintained under high vacuum overnight and then dissolved in methanol. This solution was filtered to remove a dark solid and then concentrated under vacuum. Finally, this residue was dissolved in 1,4-dioxane at 25° C. To this solution was added dropwise an excess (˜1 mL) of 4N HCl in 1,4-dioxane. The resulting precipitate was recovered by filtration and dried under vacuum to furnish 4-(pyridin-2-yl)-5,6,7,8-tetrahydropyrido[3,4-d]pyrimidine hydrochloride (0.93 g, 53%) as a brick-red solid; Mass Spec.: m/e: 213.05 (M+H)+ [calc'd: 213.11]; 1HNMR (500 MHz, DMSO-d6) δ 9.81 (br s, 2H), 9.17 (s, 1H), 8.76 (m, 1H), 8.15 (m, 1H), 7.59 (m, 1H), 4.49 (m, 2H), 3.41 (m, 4H).

1. waitat 25° C. for 20 h
2. stirringthe resulting two-phase mixture was stirred at 25° C. for 1.0 h
3. customThe phases were separated
4. washthe aqueous phase was washed with dichloromethane
5. customThe combined organic phases were dried over anhyd
6. filtrationsodium sulfate, filtered
7. concentrationconcentrated
8. dissolutionThe residue was dissolved in methanol
9. temperaturethe solution was heated
10. temperatureat reflux for 1.0 h
11. temperatureAfter cooling to room temperature the mixture
12. concentrationwas concentrated under vacuum
13. customThe residue was triturated with ethyl acetate
14. filtrationthe resulting solids were recovered by filtration
15. customdried under vacuum
16. customto provide a purple solid
17. customThe phases were separated
18. washthe aqueous phase was washed twice with chloroform
19. washThe combined organic phases were washed with brine
20. customdried over anhyd
21. filtrationsodium sulfate, filtered
22. concentrationconcentrated
23. temperatureThe residue was maintained under high vacuum overnight
24. dissolutiondissolved in methanol
25. filtrationThis solution was filtered
26. customto remove a dark solid
27. concentrationconcentrated under vacuum
28. dissolutionFinally, this residue was dissolved in 1,4-dioxane at 25° C
29. additionTo this solution was added dropwise an excess (˜1 mL) of 4N HCl in 1,4-dioxane
30. filtrationThe resulting precipitate was recovered by filtration
31. customdried under vacuum