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.

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Gangjee A, Li W, Kisliuk RL, Cody V, Pace J, Piraino J, Makin J

J Med Chem. 2009 Aug 13;52(15):4892-902. doi: 10.1021/jm900490a.

PubMed ID

19719239 [ View in PubMed

]

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.

DrugBank Data that Cites this Article

Polypeptides

Name	UniProt ID
Dihydrofolate reductase	P00374	Details

Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
10-Propargyl-5,8-Dideazafolic Acid	Thymidylate synthase	IC 50 (nM)	85	7.4	30	Details
Methotrexate	Dihydrofolate reductase	IC 50 (nM)	20	7.4	30	Details
Trimethoprim	Dihydrofolate reductase	IC 50 (nM)	>340000	7.4	30	Details