Compound can be prepared in three different ways: 1) The reduction of cytidine (I) with H2 over Rh/Al2O3 in water in a Parr apparatus at 2.8 bar gives 3,4,5,6-tetrahydrocytidine (II), which is then hydrolyzed with water at pH 5.5. 2) The reduction of uridine (III) with H2 over Rh/Al2O3 as before gives 5,6-dihydrouridine (IV), which is then reduced again with NaBH4 in water or with H2 over Rh/Al2O3 in water containing ammonia. 3) The reduction of (III) can also be performed in a single step with H2 over Rh/Al2O3 in water containing NH3, in a Parr apparatus at 2.94 bar.