If you've been like me, you had a hard time remembering the numbering of purines and pyrimidines and an even harder time thinking why they are numbered so. No more hard times :D
The article here says two simple rules for numbering a heterocyclic ring:
That's pyrimidine structure for you
And that's purine, both from wikipedia.
If you've got doubt on me, GUArdian Angels are PURe and TWO wINGED
(Guanine and Adenosine are Purines and Two Ringed)
As is evident, the Nitrogen atoms are being given the smallest numbering. Then, the carbons that are shared between cycles are given the smallest numbers. And then, the double bonds!
The article here says two simple rules for numbering a heterocyclic ring:
- Hetero atoms should have the lowest possible numbers.
- Carbon atoms which are shared by two rings should follow the lowest
possible numbers.
That's pyrimidine structure for you
And that's purine, both from wikipedia.
If you've got doubt on me, GUArdian Angels are PURe and TWO wINGED
(Guanine and Adenosine are Purines and Two Ringed)
As is evident, the Nitrogen atoms are being given the smallest numbering. Then, the carbons that are shared between cycles are given the smallest numbers. And then, the double bonds!
Why dont we take counting of rings in continuation.
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