Regular expression: "between" : and a space - regex

Question

I know there are a load of similar "combine 2 regular expressions" posts on here, but I've tried the solutions and keep getting errors.
I've got the regular expressions to parse a description such as:
Org Biomol Chem. 2011 May 7;9(9):3549-59. doi: 10.1039/c1ob05128h. Epub 2011 Mar 28.
to extract the DOI (Digital Object Identifier):
([^:]+$) --> 10.1039/c1ob05128h. Epub 2011 Mar 28.
([^\s]+) --> 10.1039/c1ob05128h.
But am pretty clueless as to how to combine these. If it's difficult, then it's not necessary, but would simplify my calculations.
I also can't figure out how to get rid of that last "." which is not part of the DOI string (for the record there may be more than 2 full stops in a DOI so the regex can't simply be "after the 2nd full stop").
Some other examples as requested:
Chem Soc Rev. 2008 Nov;37(11):2413-21. doi: 10.1039/b719548f. Epub 2008 Sep 16.
Small. 2010 Dec 20;6(24):2796-820. doi: 10.1002/smll.201001881. Review.
Org Lett. 2010 Oct 1;12(19):4248-51. doi: 10.1021/ol101920b.
Chemistry. 2010 Dec 27;16(48):14285-9. doi: 10.1002/chem.201002111. No abstract available.
All the attempts I've made so far give a result much the same as this:
Some of the exceptions to Dukeling's suggestion of "doi: ([^\s]+).? ([^:]+).?", for reasons unknown, were:
Chem Commun (Camb). 2012 Dec 25;48(99):12094-6. doi: 10.1039/c2cc35588d.
Org Biomol Chem. 2013 Jan 7;11(1):27-30. doi: 10.1039/c2ob26587g.
Chem Commun (Camb). 2013 Jan 25;49(7):671-3. doi: 10.1039/c2cc37953h.
Org Lett. 2010 Oct 1;12(19):4248-51. doi: 10.1021/ol101920b.Chemistry. 2010 Jul 26;16(28):8537-44. doi: 10.1002/chem.201000773.
Chem Commun (Camb). 2012 Dec 25;48(99):12094-6. doi: 10.1039/c2cc35588d.
Org Biomol Chem. 2013 Jan 7;11(1):27-30. doi: 10.1039/c2ob26587g.
Chem Commun (Camb). 2013 Jan 25;49(7):671-3. doi: 10.1039/c2cc37953h.
Org Lett. 2010 Oct 1;12(19):4248-51. doi: 10.1021/ol101920b.
Chemistry. 2010 Jul 26;16(28):8537-44. doi: 10.1002/chem.201000773.

Answer 1

If you only want the . gone, this seems to work:
"doi: ([^\s]+)\."
So we're just putting the . outside the brackets, so it doesn't get grouped with the string.
If you want to extract 10.1039/c1ob05128h and Epub 2011 Mar 28 in 2 separate strings, you can do this with groups. You can make the regex something like:
"doi: ([^\s]+)\.(?: ([^:]+)\.)?"
Given that the second part appears to be optional, we need to surround it with brackets which we mark as optional with ? (and the ?: makes it a non-capturing group, so you don't get that in your second cell rather than what you want).
And Google seems to automatically fill =CONTINUE(..., 1, 2) into the next cell, which gives you the two groups next to one another.
The pursuit to make the .'s optional
At first I tried just saying \.?, but obviously the [^\s]+ will then consume the . (which is not desired).
So you need to include something inside the brackets to prevent this. Specifically, you need to check the last character and make sure it's not a ..
This led me to:
"doi: ([^\s]*[^.\s])\.?(?: ([^:]*[^.:])\.?)?"
This allows for optional .'s, but if there are more than 1 . at the end, it won't work. Assuming we want none of these in our output, it's easily fixed by changing the \.? to \.*.
"doi: ([^\s]*[^.\s])\.*(?: ([^:]*[^.:])\.*)?"

Answer 2

I believe this may do the trick:
/doi: ((\S+)(?:\. .+)?)\.$/
The outermost group (which captures the longer string) is capture group 1, and the innermost group is capture group 2.

Answer 3

=REGEXEXTRACT(cell;"doi: ([.\d]+\/[\w\.]+)\.(?: |$)")
--> it extracts 10.1039/c1ob05128h
No need to combine regular expressions, it can be done at once.
I tried it on all of your examples and it works.