title: Design, synthesis, and X-ray crystal structure of classical and nonclassical 2-amino-4-oxo-5-substituted-6-ethylthieno[2,3-d]pyrimidines as dual thymidylate synthase and dihydrofolate reductase inhibitors and as potential antitumor agents.
abstract: N-{4-[(2-Amino-6-ethyl-4-oxo-3,4-dihydrothieno[2,3-d]pyrimidin-5-yl)thio]benzoyl}-L-glutamic acid 2 and 13 nonclassical analogues 2a-2m were synthesized as potential dual thymidylate synthase (TS) and dihydrofolate reductase (DHFR) inhibitors and as antitumor agents. The key intermediate in the synthesis was 2-amino-6-ethyl-5-iodothieno[2,3-d]pyrimidin-4(3H)-one, 7, to which various arylthiols were attached at the 5-position. Coupling 8 with L-glutamic acid diethyl ester and saponification afforded 2. X-ray crystal structures of 2 and 1 (the 6-methyl analogue of 2), DHFR, and NADPH showed for the first time that the thieno[2,3-d]pyrimidine ring binds in a "folate" mode. Compound 2 was an excellent dual inhibitor of human TS (IC50 = 54 nM) and human DHFR (IC50 = 19 nM) and afforded nanomolar GI50 values against tumor cells in culture. The 6-ethyl substitution in 2 increases both the potency (by 2-3 orders of magnitude) as well as the spectrum of tumor inhibition in vitro compared to the 6-methyl analogue 1. Some of the nonclassical analogues were potent and selective inhibitors of DHFR from Toxoplasma gondii.
authors.affiliation: Division of Medicinal Chemistry, Graduate School of Pharmaceutical Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, Pennsylvania 15282, USA. gangjee@duq.edu
authors.forename: Aleem
authors.initials: A
authors.lastname: Gangjee
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Roy L
authors.initials: RL
authors.lastname: Kisliuk
authors.forename: Vivian
authors.initials: V
authors.lastname: Cody
authors.forename: Jim
authors.initials: J
authors.lastname: Pace
authors.forename: Jennifer
authors.initials: J
authors.lastname: Piraino
authors.forename: Jennifer
authors.initials: J
authors.lastname: Makin
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D045744:Cell Line, Tumor; D018360:Crystallography, X-Ray; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D005493:Folic Acid Antagonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013762:Tetrahydrofolate Dehydrogenase / Q000187:drug effects*; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*; D014122:Toxoplasma / Q000201:enzymology
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D005493:Folic Acid Antagonists; D011743:Pyrimidines; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase