Diisopropylethylamine → (2s)-2-Benzyloxycarbonylamino-3-(6-(4-(5,6,7,8-tetrahydro-[1,8]naphthyridin-2-yl)-piperidin-1-yl)-purin-9-yl)-propionic acid tert-butyl ester

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Reaction Steps

0.44 g of the compound of step c) were dissolved in 5 ml of anhydrous dimethylformamide. 0.7 ml of N,N-diisopropylethylamine were added together with 0.58 g of (S)-2-benzyloxycarbonylamino-3-(6-chloro-purin-9-yl)-propionic acid tert-butyl ester, and the mixture was stirred at ambient temperature overnight. Thin layer chromatographic control exhibited only incomplete reaction. Stirring was therefore continued for 6 hours at 40° C. until the reaction was complete. The solvent was removed in vacuo and the residue was dissolved in dichloromethane and washed twice with water. The organic phase was dried with anhydrous magnesium sulfate and, after filtration, concentrated in vacuo. The raw material was chromatographed on silica gel with ethyl acetate and ethyl acetate/methanol (1:10). Yield: 224 mg.

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