Dck Simplify The Exploration Of Structural Analogues Of Hiv And Vegf Inhibitory Activity

Suksdorfin (1), a natural product isolated from the fruit of Lomatium Suksdorfii, has an angular pyranocoumarin skeleton with interesting biological properties, especially its anti-HIV activity (EC₅₀ = 2.6±2.1μM, TI = 30.6±22.4μM, TI = therapeutic index IC50 / EC50). Structural modification of 1 yielded DCK (2) and 4-methyl-DCK (6), which demonstrated extremely potent inhibitory activity against HIV-1 replication in H9 lymphocytic cells (EC₅₀ = 4×10^-4μM, TI = 136719 and EC₅₀ = 1.57×10^-7μM, TI > 10⁹, respectively).The recent mechanistic studies indicated that HIV-1 RT is possibly the target of DCK and DCK is a unique HIV-1 RT inhibitor that inhibits the DNA-dependent DNA polymerase activity. In contrast, DCK did not significantly affect the RNA-dependent DNA polymerase activity. Due to its unique mode of action, DCK and its derivatives could be used to functionally dissect HIV-1 RT and might have the potential to be clinically useful. Accordingly, selected modifications on DCK skeleton are highly desirable in order to identify the pharmacophores in this class of potent anti-HIV agents and explore the structural aspect of the target bio-molecule(s). To this end, a variety of novel DCK analogs containing O,N-, O,S-, S,O- or O,C- by displacing the O,O- atoms in the DCK skeleton were synthesized previously in our group. The structural modifications of 4-methyl-DCK by replacing the ring oxygen atom of DCK with a sulfur or a carbon atom (53a, 52c, 55c, 56) and the five-membered-C-ring DCK analogs (56 and 57) demonstrated that these analogs also exhibited potent inhibitory effects on HIV-1 replication in H9 lymphocytes. However, the poor water solubility of DCK and its active analogs could limit their further development as anti-HIV drug candidates. As a continuous effort towards the development of this type of potential anti-HIV drugs, a new series of simplified DCK analogs, namely dihydrofurocoumarin derivatives and indane derivatives, were designed based on the principle of bioisomerism. In order to further explore the effect of the ring C and 9-founctional groups on the anti-HIV activity we attempt to synthesize a new series of DCK analogues (11-19) with a furan ring replacing the original pyran ring C in the DCK skeleton and introducing moiety of oxime ester group into the DCK structure. The studies on the SAR of these compounds might provide the useful information for understanding the ring C as well as the 9-position substituted groups. We also attempt to synthesize a new series of indane derivatives with the modification of 7-position and introduction of 1-position large camphanoyl ester group to explore the impact of ring A and C to anti-HIV activity. The target compounds, namely dihydrofurocoumarin derivatives and indane derivatives, were accomplished in several steps with the synthesis by using 7-hydroxy-4-methyl-2H-chromen-2-one and phenol as the starting material respectively. The structures of all these target simplified DCK analogs were confirmed by various spectral analyses, including ¹H NMR, ¹³C NMR, and mass spectra.The anti-HIV activities of indane derivatives and some of the dihydrofurocoumarin derivatives were tested in H9 lymphocytes with AZT as a reference compound. The preliminary bioassay data indicated that only a few compounds showed low anti-HIV activity, most of these compounds displayed no anti-HIV activity. The results of these simplified DCK analogs with replacement of pyran ring C by dihydrofuran or cyclopentane ring C demonstrated that to shorten ring C might be the cause of low anti-HIV activity. There is probably only a small space after shortening ring C and the pharmacophore in this region might inhibit the binding of big molecular then had an impact of these compounds.Most of the target compounds were tested in the single human breast cancer cell MDA-MB-231 with 2-ME as a reference compound. The preliminary bioassay data indicated that dihydrofurocoumarin derivatives showed no VEGF inhibitory activity while indane derivatives indicated good bioactivity. Compound 25, 110, 111 and 112 demonstrated obvious VEGF inhibitory activity with IC₅₀ = 432μg/ml (1.122 mM), EC₅₀ = 50.5μg/ml (0.131 mM), TI = 8.55; IC₅₀> 500μg/ml (>1.309 mM), EC₅₀ = 70.9μg/ml (0.169 mM), TI >7.05; IC₅₀> 1200μg/ml (> 4.741 mM), EC₅₀ = 165.9μg/ml (0.655 mM), TI >7.23 and IC₅₀>1100 (>4.118 mM), EC₅₀ = 126.2 (0.472 mM), TI >8.72. These bioassay results suggested that the compounds with 7-position acetoxy or benzyloxy group showed more obvious VEGF inhibitory activity than the compounds with methoxy group. And the compound with 1-O-benzyl oxime group showed obvious inhibitory activity. The impact of the 1 - or 7- substituent group to VEGF activity should have a further study.During the synthesis of the target molecules, we also disclosed a series of interesting chemical reaction features, which are summarized as follows:(1). The esterifications of 9-(hydroxyimino)-4-methyl-8,9-dihydrofuro[2,3-h] chromen-2-one (36) with acid chlorides were found to afford normal oxime-esters 15-19 in acceptable yields in presence of excessive 4-dimethylaminopyridine as the acid scavenger, whereas the reactions gave unexpected 8-substituted products N-(8-chloro-4-methyl-2-oxo-2H-furo[2,3-h] chromen-9-yl)amides (61-63) and 4-methyl-2,9-dioxo-8,9-dihydro-2H-furo[2,3-h] chromen-8-ylcarboxyloates (64-65) by using excessive acid chlorides. The possible mechanism for the formation of unexpected products 61-63 and 64-65 was proposed and the 5 compounds might be provided for bioassay.(2). Reductions of compound 45 and 44 with NaBH₄ or NaBH₃CN were examined and 2,3-dihydro-1H-indene-1,7-diol (71) or 2,3-dihydro-1H-inden-4-ol (70) was obtained as the main product under different conditions. The possible mechanism of the reduction of carbonyl to methylene group was also proposed.(3). Reductions of 7-methoxy-2,3-dihydroinden-l-one oxime (41) was studied, and we found that the aluminium amalgam is a good way to the reduction of oxime.The study mentioned above provided valuable information on the synthesis and chemical properties of these new types of heterocyclic compounds.