Purine and its substitution derivatives, especially naturally occurring examples. The customary numbering shown below is not systematic.
purine
Source:
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995))
on page 1361
Transformed and rewritten from PDF version (entry
http://www.iupac.org/goldbook/P04953.pdf)
by: Miloslav Nic, Jiri Jirat, Bedrich Kosata, ICT Prague, Czech Republic