A mixture of (−)-(R)-3,4-dihydro-2H-1-benzopyran-2-carbonyl chloride (0.2 mol) and magnesium oxide (40 g) in ethyl acetate (350 ml) was hydrogenated at 25° C. with palladium on activated carbon (10%) (5 g) as a catalyst in the presence of a solution (4%) of thiophene in methanol (5 ml). After uptake of H2 (1 eq.), the catalyst was filtered off and the filtrate was collected in a mixture of potassium acetate (7 g) in methanol (200 ml). A mixture of 1-(3-aminopropyl)-tetrahydro-2(1H)pyrimidinone (0.2 mol) in methanol (200 ml) was added and the mixture was hydrogenated (16 hours at 25° C.; 16 hours at 50° C.) with rhodium on activated carbon (5%, 3 g) as a catalyst in the presence of a solution (4%) of thiophene in methanol (3 ml). After uptake of hydrogen, the catalyst was filtered off and the filtrate was evaporated. The residue was stirred in water, treated with 50% NaOH, and extracted with DCM. The separated organic layer was dried, filtered and the solvent evaporated. The residue was stood overnight in 2-propanone (500 ml). The supernatant was decanted off and the residue was purified by column chromatography over silica gel (eluent: CH2Cl2/(CH3OH NH3) 95/5). The desired fractions were collected and their solvent was evaporated, yielding (R)-1-[3-[[(3,4-dihydro-2H-1-benzopyran-2-yl)-methyl]amino]propyl]tetrahydro-2(1H)-pyrimidinone (comp. 2).
