“One pot” synthesis of 2‐substituted 9‐(2′‐hydroxy‐3′‐aminopropyl)‐8‐azahypoxanthines and 8‐azaadenines (5‐substituted 3‐(2′‐hydroxy‐3′‐aminopropyl) 7‐amino and 7‐hydroxy‐3H‐1,2,3‐triazolo[4,5‐d]pyrimidines)