Structure-based design, synthesis and preliminary evaluation of selective inhibitors of dihydrofolate reductase from Mycobacterium tuberculosis

Abstract

Tuberculosis is an increasing threat, owing to the spread of AIDS and to the development of resistance of the causative organism, Mycobacterium tuberculosis, to the currently available drugs. Dihydrofolate reductase (DHFR) is an important enzyme of the folate cycle; inhibition of DHFR inhibits growth and causes cell death. The crystal structure of M. tuberculosis DHFR revealed a glycerol tightly bound close to the binding site for the substrate dihydrofolate; this glycerol-binding motif is absent from the human enzyme. A series of pyrimidine-2,4-diamines was designed with a two-carbon tether between a glycerol-mimicking triol and the 6-position of the heterocycle; these compounds also carried aryl substituents at the 5-position. These, their diastereoisomers, analogues lacking two hydroxy groups and analogues lacking the two-carbon spacing linker were synthesised by acylation of the anions derived from phenylacetonitriles with ethyl (4S,5R)-4-benzyloxymethyl-2,2-dimethyl-1,3-dioxolane-4-propanoate, ethyl (4S,5S)-4-benzyloxymethyl-2,2-dimethyl-1,3-dioxolane-4-propanoate, tetrahydrooxepin-2-one and 2,3-O-isopropylidene-d-erythronolactone, respectively, to give the corresponding alpha-acylphenylacetonitriles. Formation of the methyl enol ethers, condensation with guanidine and deprotection gave the pyrimidine-2,4-diamines. Preliminary assay of the abilities of these compounds to inhibit the growth of TB5 Saccharomyces cerevisiae carrying the DHFR genes from M. tuberculosis, human and yeast indicated that 5-phenyl-6-((3R,4S)-3,4,5-trihydroxypentyl)pyrimidine-2,4-diamine selectively inhibited M. tuberculosis DHFR and had little effect on the human or yeast enzymes.

4-Hydroxy-2-quinolones. 154*. Pyrimidin- 2-ylamides of 1-r-4-hydroxy-2-oxo-1,2-dihydro- quinoline-3-carboxylic acids. synthesis, structure, and properties

“…For an unambiguous solution as to which bromination route had occurred X-ray structural analysis was carried out and it was unexpectedly found that the product is just the starting pyrimidin-2-ylamide 1c (see Figure 1, Tables 3 and 4). The bicyclic fragment, hydroxyl, carbamide, and carbonyl groups as well as atom C (15) (2) and N(1)-C(1) 1.390(2) Å when compared with their mean values of 1.353 and 1.371 Å respectively and this has been observed in previously studied quinolone series compounds. An alkyl substituent is placed such that the C(15)-C(16) bond is virtually perpendicular to the plane of the bicyclic fragment (torsional angle C(9)-N(1)-C(15)-C(16) 95.5(2)º).…”

“…In particular, many publications relate to the search for novel and efficient antimycobacterial agents [11][12][13][14][15][16] and this is explained by an exceptionally high surge in tubercular morbidity, approaching an epidemic scale in many countries of the world. In many examples of this kind it is necessary to include also the tendency of stimulation of the tubercular mycobacterium to active mutation contributing to rapid formation of resistance (often multiple) to known antitubercular medicines.…”

Mycobacterium tuberculosis Folate Metabolism and the Mechanistic Basis for para -Aminosalicylic Acid Susceptibility and Resistance

“…Several studies have focused on the identification of new M. tuberculosis DHFR inhibitors that have more potent antitubercular activity than trimethoprim (37,71,74,75). Suling et al screened a series of lipophilic deazapteridine derivatives with structural similarity to trimethoprim and identified several M. tuberculosis DHFR inhibitors with improved activity relative to that of trimethoprim in cell-free and whole-cell assays (71).…”

Preparation, biological evaluation and molecular docking study of imidazolyl dihydropyrimidines as potential Mycobacterium tuberculosis dihydrofolate reductase inhibitors

“…DHFR may not be a novel target, but it cannot be ignored as there is ample enthusiasm for the development of DHFR inhibitors, particularly with regard to mycobacteria. [18][19][20][21][22][23][24] This distinctive feature of DHFR makes it an ideal target for rational and effective drug design for antitubercular agents.…”