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Just to give you a bit of context, I don't have any background in Chemistry. I'm actually a Computer Scientist adventuring myself in the world of Chemoinformatics (more specifically, we're developing algorithms to improve drug discovery).

I noticed that many molecules (or at least drug-like molecules) have rings, but I was wondering: from an evolutionary perspective, what does it mean? Why did molecules evolve to have this "feature", do molecules with rings have better properties then similar ones without rings?

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    $\begingroup$ Molecules do not evolve. As for the rings, they are there for purely combinatorial reasons. Also, not even all classes of biomolecules have them; fats, for example, have none. $\endgroup$ Nov 26, 2015 at 12:33
  • $\begingroup$ Welcome to chemistry.stackexchange.com. Feel free to take a tour of the site. $\endgroup$
    – Jan
    Nov 26, 2015 at 12:56

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I noticed that most molecules (or at least drug-like molecules) have rings, but I was wondering: from an evolutionary perspective, what does it mean?

First note: Delete the ‘most molecules’ bit. The numbers are insane and nigh uncountable, but non-cyclic molecules are similarly common as cyclic ones are.

From an evolutionary persective this means: nothing.

Drugs are designed to inhibit certain enzymes as specifically as possible. The enzyme has a shape that happens to best fulfil it’s purpose according to evolutionary principles. (my draft had ‘design’ here for a second, but it would be the wrong word choice. Nature and evolution do not design.) This will render an active pocket having a certain orientation, size and hydrophobic pattern that drug designers attempt to mimick. If a (poly-) cyclic molecule fits well, it fits well. If a linear molecule fits better it fits better. Think of it as trial and error.

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    $\begingroup$ Come to think of it, your explanation actually provides a reason why the cyclic structures may be somewhat preferable. See, a (poly)cyclic molecule tends to have less conformational freedom than a similarly large non-cyclic one. If it fits, it fits. $\endgroup$ Nov 26, 2015 at 13:29
  • $\begingroup$ @IvanNeretin I’m pretty much d’accord with you there. But if a (strained?) linear one fits, it’ll fit similarly and some macrocycles are rather flexible, so it’s not part of my argument ;) $\endgroup$
    – Jan
    Nov 26, 2015 at 13:58

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