Imidazole continued 2.4.5- trimethyl

It is easily possible to continue to insert nitrogen atoms into fused ring systems and some important compounds belong to these groups. The purines are part of DNA and RNA and are treated in Chapter 49, but simple purines play an important part in our lives. Coffee and tea owe their stimulant properties to caffeine, a simple trimethyl purine derivative. It has an imidazole ling fused to a pyrimidine ring and is aromatic in spite of the two carbonyl groups. 

---