Design, Synthesis, and Biological Evaluation of Classical and Nonclassical 2-Amino-4-oxo-5-substituted-6-methylpyrrolo[3,2-d]pyrimidines as Dual Thymidylate Synthase and Dihydrofolate Reductase Inhibitors

Abstract

We designed and synthesized a classical antifolate N-{4- [(2-amino-6-methyl-4-oxo-3,4-dihydro-5H-pyrrolo[3,2-d]pyrimidin-5-yl)methyl]benzoyl}-L-glutamic acid 4 and 11 nonclassical analogues 5-15 as potential dual thymidylate synthase (TS) and dihydrofolate reductase (DHFR) inhibitors. The key intermediate in the synthesis was N- (4-chloro-6-methyl-5H-pyrrolo[3,2-d]pyrimidin-2-yl)-2,2-dimethylpropanamide, 29, to which various 5-benzyl substituents were attached. For the classical analogue 4, the ester obtained from the N-benzylation reaction was deprotected and coupled with diethyl L-glutamate followed by saponification. Compound 4 was a potent dual inhibitor of human TS (IC 50 = 46 nM, about 206-fold more potent than pemetrexed) and DHFR (IC 50 = 120 nM, about 55-fold more potent than pemetrexed). The nonclassical analogues were marginal inhibitors of human TS, but four analogues showed potent T. gondii DHFR inhibition along with >100-fold selectivity compared to human DHFR.

Potent Dual Thymidylate Synthase and Dihydrofolate Reductase Inhibitors: Classical and Nonclassical 2-Amino-4-oxo-5-arylthio-substituted-6-methylthieno[2,3-d]pyrimidine Antifolates

“…These result parallel the structure–activity relationship (SAR) we recently reported for the nonclassical N5-substituted 2-amino-4-oxo-6-methylpyrrolo[3,2- d ]pyrimidines against DHFR. 48 The excellent selectivity of compound 8 against T. gondii DHFR attests to the fact that differences in mammalian and pathogen DHFR can be exploited with nonclassical DHFR inhibitors. We are in the process of developing other nonclassical TS inhibitors with potential selectivity toward nonmammalian DHFR and TS and other analogues as antitumor agents.…”

Antiproliferative activities of halogenated pyrrolo[3,2-d]pyrimidines

“…The 9-deazapurines have also been explored in the past as nucleoside isosteres and these efforts have resulted in the design of purine nucleoside phosphorylase (PNP) inibitors, 7,13–22 dihydrofolate reductase (DHFR) inhibitors 23,24 and more recently for kinase inhibition (Fig. 1b).…”

Novel Water-Soluble Substituted Pyrrolo[3,2-d]pyrimidines: Design, Synthesis, and Biological Evaluation as Antitubulin Antitumor Agents

“…N -(4-Oxo-4,5-dihydro-3 H -pyrrolo[3,2- d ]pyrimidin-2-yl)pivalamide (11) ( 13 , 1.16 g, 4.67 mmol) was added to phosphorus oxychloride (30 mL) and heated at reflux for 3 h. The solvent was evaporated in vacuo, and the pH of the residue was adjusted to 8 with ammonia solution. The resulting precipitate was filtered and purified by column chromatography (CHCl 3 : MeOH; 50:1; v/v) to give a white solid (1.1 g, 86%).…”

“…Compounds 12 (10) and 13 (11) (Scheme 1) were chlorinated with phosphorus oxychloride to generate 14 and 15 , respectively. Compounds 14 , 16 (12) and 17 (13) were subjected to nucleophilic displacement reactions using appropriately substituted anilines to afford 3 – 8 and 11 , which were in turn converted to their hydrochloride salts using hydrogen chloride gas.…”