Development of substituted pyrido[3,2-d]pyrimidines as potent and selective dihydrofolate reductase inhibitors for pneumocystis pneumonia infection

SnAr Reactions of 2,4-Diazidopyrido[3,2-d]pyrimidine and Azide-Tetrazole Equilibrium Studies of the Obtained 5-Substituted Tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines

A straightforward method for the synthesis of 5-substituted tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines from 2,4-diazidopyrido[3,2-d]pyrimidine in SnAr reactions with N-, O-, and S- nucleophiles has been developed. The various N- and S-substituted products were obtained with yields from 47% to 98%, but the substitution with O-nucleophiles gave lower yields (20-32%). Furthermore, the fused tetrazolo[1,5-a]pyrimidine derivatives can be regarded as 2-azidopyrimidines and functionalized in copper(I)-catalyzed azide-alkyne dipolar cycloaddition (CuAAC) and Staudinger reactions due to the presence of a sufficient concentration of the reactive azide tautomer in solution. In total, seven products were fully characterized by their single crystal X-ray studies, while five of them were representatives of the tetrazolo[1,5-a]pyrido[2,3-e]pyrimidine heterocyclic system. Equilibrium constants and thermodynamic values were determined using variable temperature ¹H NMR and are in agreement of favoring the tetrazole tautomeric form (ΔG₂₉₈ = -3.33 to -7.52 (kJ/mol), ΔH = -19.92 to -48.02 (kJ/mol) and ΔS = -43.74 to -143.27 (J/mol·K)). The key starting material 2,4-diazidopyrido[3,2-d]pyrimidine presents a high degree of tautomerization in different solvents.

Dihydrofolate reductase inhibitors: patent landscape and phases of clinical development (2001-2021)

INTRODUCTION

Dihydrofolate reductase (DHFR) plays an important role in the biosynthesis of amino acid and folic acid. It participates by reducing dihydrofolate to tetrahydrofolate, in the presence of nicotinamide dinucleotide phosphate cofactor, and has been verified by various clinical studies to use DHFR as a target for the treatment of cancer and various bacterial infections.

AREA COVERED

In this review, we have disclosed patents of synthetics and natural DHFR inhibitors with diaminopyrimidine and quinazoline nucleus from 2001. Additionally, this review highlights the clinical progression of numerous DHFR inhibitors received from the last five years.

EXPERT OPINION

From 2001 to 2021, numerous active chemical scaffolds have been introduced and are exposed as lead candidates that have entered clinical trials as potent DHFR inhibitors. Moreover, researchers have paid considerable attention to the development of a new class of DHFR inhibitors with higher selectivity and potency. This development includes synthesis of synthetic as well as natural compounds that are potent DHFR inhibitors. On the basis of literature review, we can anticipate that there are a huge number of novel active molecules available for the future that could possess superior abilities to target this enzyme with a profound pharmacological profile.

Electronic properties investigation of human dihydrofolate reductase complexes with ligands

Despite the fact that there are already drugs for cancer, they still show strong toxicity to the human organism. That is why it is necessary to establish the factors affecting activity in order to develop new, more effective drugs aimed at tumor cells, minimizing harm to healthy cells. The present research is based on electronic properties calculation of the complexes using AlteQ approach. In the focus of this study are complexes of human dihydrofolate reductase (hDHFR) with a series of known inhibitors bound in the active site. Further, a statistical analysis was performed to establish the relationships between a myriad electronic characteristics and IC₅₀. The change in total volume and the change of own electrons number of hydrogen atoms in their atomic basins are identified as the descriptors correlating the most with the hDHFR inhibition potency. Additionally, two lipophilic parts of protein (Thr56, Ser59, Ile60 and Ile7, Val8, Ala9) were found, which act as a key factor in decreasing bioactivity. The depth analysis of intermolecular interactions showed that the interactions between water molecules and ligand play a crucial role in hDHFR inhibition. Furthermore, the molecular dynamics simulations were used for deeper understanding of the structural inhibition, each for 50 ns time scale in explicit water conditions. Thus, the AlteQ approach made it possible to determine the factors influencing the activity and evaluate them not only qualitatively, but also quantitatively.Communicated by Ramaswamy H. Sarma.