Metopen

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:44185
http://www.hmdb.ca/metabolites/HMDB0014703
http://www.genome.jp/dbget-bin/www_bget?drug:D00142
http://www.genome.jp/dbget-bin/www_bget?cpd:C01937
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=126941
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46507678
https://www.chemspider.com/Chemical-Structure.112728.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=66082
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=6851
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=44185
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL34259
https://zinc.docking.org/substances/ZINC000001529323
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DNC000933
http://www.pharmgkb.org/drug/PA450428
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/MTX
http://www.rxlist.com/cgi/generic/mtx.htm
https://www.drugs.com/methotrexate.html
http://www.pdrhealth.com/drug_info/rxdrugprofiles/drugs/met1257.shtml
https://en.wikipedia.org/wiki/Methotrexate