An efficient method for the preparation of 8-(polyhydroxyalkyl)-7H-purine-2,6(1H,3H)-diones 5 starting from 6-chloro-1,3-dimethylpyrimidine-2,4(1H,3H)-dione (1) and 1-amino-1-deoxypentitols or -hexitols 2 via 1,3-dimethyl-6-(polyhydroxyalkylamino)-pyrimidine-2,4(1H,3H)-diones 3 and their 5-nitrosoderivatives 4 is described.