Guaranine

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:27732
http://www.genome.jp/dbget-bin/www_bget?cpd:C07481
http://metacyc.org/META/new-image?type=COMPOUND&object=1-3-7-TRIMETHYLXANTHINE
http://www.hmdb.ca/metabolites/HMDB0001847
http://www.genome.jp/dbget-bin/www_bget?drug:D00528
http://www.genome.jp/dbget-bin/www_bget?cpd:C07481
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=2519
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46506408
https://www.chemspider.com/Chemical-Structure.2424.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=10849
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=1886
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=27732
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL113
https://zinc.docking.org/substances/ZINC000000001084
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP000099
http://www.pharmgkb.org/drug/PA448710
http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=407
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/CFF
http://www.rxlist.com/cgi/generic3/caffeine.htm
https://www.drugs.com/caffeine.html
https://en.wikipedia.org/wiki/Caffeine