1-(1′-(tert-Butyl)-1′,2′,3′,4′,5′,6′-hexahydro-3,4′-bipyridinyl-6-yl)-1,2,3,4-tetra-hydroquinoxaline (0.12 g, 0.35 mmol) is placed in 3.5 ml of dichloromethane at 0° C. Triethylamine (0.10 ml, 0.7 mmol) and then triphosgene (0.041 g, 0.14 mmol) are added. The reaction medium is stirred at ambient temperature for 3 h. 3.5 ml of DMF, diisopropylethylamine (0.15 ml, 0.87 mmol) and then 4-aminoadamantane-1-carboxylic acid amide hydrochloride (0.08 g, 0.35 mmol) are then added. The reaction medium is heated at 50° C. for 18 h under nitrogen. After hydrolysing on 40 ml of H2O and extracting with ethyl acetate, the organic phase is washed with water and then with a saturated aqueous sodium chloride solution, dried over MgSO4 and concentrated to dryness. The crude product obtained is chromatographed on silica gel, elution being carried out with an ethyl acetate/methanol/aqueous ammonia gradient in dichloromethane varying from 100/0/0/0 to 7/2.5/0.5/0.5 (dichloromethane/ethyl acetate/methanol/aqueous ammonia). 0.09 g of 4-(1′-(tert-butyl)-1′,2′,3′,4′,5′,6′-hexahydro-3,4′-bipyridinyl-6-yl)-3,4-dihydro-2H-quinoxaline-1-carboxylic acid (5-carbamoyladamantan-2-yl)amide is obtained and is subsequently triturated from diethyl ether. The crystals obtained are filtered off and dried.
