5a

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:6775
http://www.hmdb.ca/metabolites/HMDB0014389
http://www.genome.jp/dbget-bin/www_bget?drug:D00377
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=4075
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46509142
https://www.chemspider.com/Chemical-Structure.3933.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=60918
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=52582
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=6775
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL704
https://zinc.docking.org/substances/ZINC000000001688
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP000729
http://www.pharmgkb.org/drug/PA450384
http://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=2700
http://www.rxlist.com/cgi/generic2/canasa.htm
http://www.pdrhealth.com/drug_info/rxdrugprofiles/drugs/row1389.shtml
https://en.wikipedia.org/wiki/Mesalazine