A new series of pyrimidones with C and C modifications
A new series of pyrimidones (14) with C-7 and C-9 modifications were furnished consisting of a hydroxypyridinone and a thiazole ring and checked against raltegravir resistant HIV mutant strains to determine their in vitro anti-HIV IN potency. Compounds 14a–14a, 14b–14b and 14c–14c appeared with 6.4 nM, 9.5 nM, 10.5 nM, 8.5 nM, 21 nM, 7.1 nM, 4.3 nM, 24 nM, 11.5 nM, 7.5 nM, 16.5 nM, 22 nM, 24 nM, 19.5 nM, 3.5 nM, 11.5 nM, 27 nM, 6.8 nM, 12.5 nM, 6.1 nM, 6.6 nM and 5.5 nM of EC50s in a HIV replication assay, respectively. Considering these initial assessment potencies, these derivatives were further subjected to check their HIV IN inhibitory efficacies, in which 15–70 nM, 19–90 nM and 3.5–6.8 nM of IC50s were observed for analogues 14a, 14b and 14c, respectively. Compound 14c turned out highly potent analogues, hence confirming the inclusion of nitrogen-based cyclic substitutions was crucial for achieving potency, because some analogues from 14a, 14b and 14c furnished 18–800 nM and 9.7–200 nM, 21–243 nM and 8.9–32.5 nM as well as 21–40.5 nM and 4.9–8.9 nM of IC50s against double mutants Q148HG140S and N155HE92Q HIV IN strains, respectively. The work validated thiazole-pyridinone molecular structures as potential leads for developing a second-generation integrase inhibitors for resistant viruses . Some bicyclic pyrimidones (15) were generated, in which at first instance nine different scaffolds designs were employed as 15a–i, particularly in detailed SAR, various ED and EWD groups were introduced at C9 position of 15a type derivatives furnishing 15j and 15k compounds, respectively. Compounds 15a–15a15b, 15e, 15f and 15h (R2 = H) showed 0.445 μM, 0.080 μM, 0.587 μM, 0.0768 μM, 0.626 μM, 1.13 μM and 5.1 μM of IC50s, respectively against wild type HIV infected T-cells. Analogues (15j) with ED groups at C-9 appeared with 80–429 nM of IC50s, whereas substitution of EWD at C-9 resulted in compounds (15k) with IC50s ranging from 85 to 195 nM. Analogues 15j and 15k exhibited 5–730 nM and 6–19.8 nM of EC50s against HIV replication in 10% FBS, respectively. The most potent Leupeptin of the series was analogue 15k with 3 nM and 4 nM of EC50s against HIV replication in 10% FBS and 50% NHS, respectively, which was better than control drug Raltegravir with 9.4 nM and 7.1 nM of EC50s, respectively . Such 6:6 bicyclic scaffold optimization equipped positive improvements in the antiviral activity of resultant compounds superior to that of raltegravir control. The same group attempted further derivatization of the pyrimidone scaffolds in terms of azoles (16a) or in terms of C-9 substitution to these pyrimidine–azole complexes (16b, 16c and 16d). All compounds were screened initially in an enzymatic assay using recombinant HIV integrase of wild-type in which compounds 16a–16a demonstrated 20 nM, 59 nM and 45 nM of IC50s, respectively, whereas analogues 16b, 16b, 16d, 16d showed 42 nM, 36 nM, 35 nM and 47 nM of IC50s, respectively. The potent analogues were further examined for their anti-HIV replication efficacies, in which 16a, 16a and 16b expressed 16.5 nM, 6.0 nM and 4.35 nM of EC50s, respectively. It was observed that insertion of the thiazole, oxazole and imidazole was most beneficial for anti-HIV IN potencies, whereas, the presence of nitrogen atom rather than sulfur and oxygen atom in the azole ring has played key role in the activities . N-3 Hydroxylated pyrimidine-2,4-diones (17) were furnished to check their rationally designed anti-HIV dual inhibitory effects against RT and IN. In this context, compounds 17a–17a, 17b, 17c and 17d showed >333 of IC50s against HIV IN 3′-processing as well as 21 μM, 7.3 μM, 3.5 μM, 5.5 μM, 8.2 μM, >333 μM, 85 μM and 105 μM of IC50s against HIV IN strand transfer, respectively. Additionally, these analogues represented anti-HIV replication efficacies with EC50s, 0.0080 μM, >10 μM, 0.024 μM, >10 μM, 1.1 μM, >10 μM, 4.3 μM and >10 μM, respectively, revealing themselves as potential leads as anti-HIV dual inhibitors with anti-HIV RT inhibitory IC50s ranging from 0.17 to >100 μM . In continuation, the same research group studied further variations along N-3 Hydroxylated pyrimidine-2,4-diones (18) in order to produce a more diverse class of potent anti-HIV IN inhibitors. The research work included yielding of new such compounds (18a) to study effects of aromatic and chelating domains on in inhibition as analogues 18a–18a showed 21 ± 2 μM, 4.8 ± 0.7 μM, 2.3 ± 0.6 μM and 3.5 ± 0.6 μM of IC50s, respectively against HIV IN strand transfer, however, in all cases IC50 values were >111 against 3′-processing. Study on effects of hydrophobic domain (18b, 18c, 18d and 18e) on in inhibition resulted in compounds 18b, 18b, 18c, 18b, 18b, 18b, 18c, 18d, 18e, 18d, 18d and 18e showed 21 ± 2 μM, 7.3 ± 0.8 μM, 5.5 ± 0.7 μM, 8.2 ± 1.0 μM, 75 ± 7 μM, 36 ± 6 μM, 11 ± 0.8 μM, 32 ± 6 μM, 73 ± 12 μM, 28 ± 2 μM, >111 μM and 24 ± 3 μM of anti-HIV IN strand transfer IC50s, respectively, whereas pour inhibitory potential against 3′-processing with >111 μM of IC50s. In addition, studies within effects of linker domain furnished compounds 18e–18e with 3.5 ± 0.6 μM, 1.6 ± 0.2 μM, 3.2 ± 0.5 μM, 4.5 ± 0.4 μM, 22 ± 0.5 μM, 46 ± 6 μM, 0.44 ± 0.1 μM and 0.56 ± 0.04 μM of IC50s against HIV IN strand transfer, respectively. SAR concluded from these studies that the OH group at N-3 position in addition to the presence of N1-4-F-benzyl moiety is the key structural requirement for IN inhibition, whereas, both the nature and the length of the linker greatly impact IN binding as CH2OCH2 linker established highest potency in this research work . 6-Benzoyl-3-hydroxypyrimidine-2,4-diones (19) were further equipped by the same research group  and checked against HIV RT and IN for their in vitro inhibitory potencies. Compounds 19i–19vi indicated 0.5–23 μM of IC50s against RT and >111 μM of IC50s against HIV IN 3′-processing. Against HIV IN strand transfer, these compounds demonstrated 37 ± 6 μM, 25 ± 3 μM, 21 ± 3 μM, 41 ± 4 μM, 41 ± 0.2 μM and 7.0 ± 0.8 μM of IC50s, respectively. From the bioassay results, it can be stated that introducing a benzoyl group at the C-6 position of the pyrimidone ring would be beneficial and lead to encouraging results within anti-HIV IN drug discovery.