Development of Small-Molecule Modulators of Nucleotide Metabolism Enzymes
In chapter 1, strategies toward the asymmetric synthesis of a deoxycytidine kinase (dCK) inhibitor are presented. Small molecule dCK inhibitors are potential cancer therapeutics: in combination with inhibition of the de novo deoxyribonucleotide triphosphate biosynthetic pathway, they have been shown to be effective against acute lymphoblastic leukemia in animal models. Our group previously identified a series of chiral dCK inhibitors, of which only the R-enantiomer is responsible for kinase inhibition; we thus sought an asymmetric synthesis of these molecules. We pursued a synthetic route in which an SN2 substitution at the chiral center occurs early in the synthesis, to avoid racemization due to a competing SN1 mechanism, which has been observed in a previous asymmetric synthesis from our group. We utilized (–)-ethyl L-lactate as a starting material, as it contains the required chiral carbon skeleton as well as readily-transformable functional groups. Our initial efforts using a Takai-Utimoto olefination as a key step were unsuccessful. Further strategies were hindered by the reactivity of the 4,6-diaminopyrimidine moiety introduced through the early substitution reaction, and ultimately a successful route was not reached.
In chapter 2, the development of ⍺-N-heterocyclic carboxaldehyde thiosemicarbazone (HCT) compounds as anti-proliferative agents is described. HCTs have long been known to have anti-cancer properties, due to various mechanisms which generally involve chelation to a redox active metal. One notable HCT which is an iron chelator is Triapine (3-AP), which is the most promising currently-available ribonucleotide reductase inhibitor. Despite currently being in Phase II clinical trials, 3-AP has poor pharmacokinetic properties, so we developed a series of 3-AP analogs which retain the pyridine scaffold of 3-AP but have modifications on the terminal amine of the thiosemicarbazone. None had significantly improved properties over 3-AP, however. HCTs with an isoquinoline scaffold have also previously been developed as ribonucleotide reductase inhibitors but were not pursued clinically due to poor drug-like properties. We synthesized a series of isoquinoline-based HCTs, several of which synergize strongly with physiologically relevant levels of Cu(II) supplementation. The lead compound 2-79 exhibits nanomolar IC90 values in the presence of copper, giving it potential as a cancer therapeutic.