Fenlips

https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:7956
http://www.hmdb.ca/metabolites/HMDB0014444
http://www.genome.jp/dbget-bin/www_bget?drug:D05407
http://www.genome.jp/dbget-bin/www_bget?cpd:C07417
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=4725
https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=46506498
https://www.chemspider.com/Chemical-Structure.4563.html
http://www.bindingdb.org/bind/chemsearch/marvin/MolStructure.jsp?monomerid=50210804
https://mor.nlm.nih.gov/RxNav/search?searchBy=RXCUI&searchTerm=59839
https://www.ebi.ac.uk/chebi/searchId.do?chebiId=7956
https://www.ebi.ac.uk/chembldb/index.php/compound/inspect/CHEMBL1540
https://zinc.docking.org/substances/ZINC000000001899
http://bidd.nus.edu.sg/group/cjttd/ZFTTDDRUG.asp?ID=DAP000488
http://www.pharmgkb.org/drug/PA450839
https://www.ebi.ac.uk/pdbe-srv/pdbechem/chemicalCompound/show/PE2
http://www.rxlist.com/cgi/generic3/penciclovir.htm
https://www.drugs.com/cdi/penciclovir.html
https://en.wikipedia.org/wiki/Penciclovir