Design,Synthesis And Evaluation Of3-Niro-2H-Chromenes As Phosphatidylinositol-3-Kinase Inhibitors

Malignant tumor is a class of disease that is seriously harmful to human health. As the traditional cytotoxic anticancer drugs usually have low selectivity, severe toxicity and other side effects, the anticancer drug developments are currently transferring from cytotoxic to targeted agents based on the mechanisms of tumorigenesis. Selected proteins or genes which are bound up with tumorigenesis, growth, metastatasis and apoptosis are becoming possible drug screening targets, and the developments of novel single-targeted or multi-targeted anticancer drugs are the main subjects in cancer therapies. Molecular oncology shows that cancerigenesis occurs when there are problems in the process of the regulating molecular signal transfering from cell surface to the nucleu, and that leads to the cell growth run out of control. Thus the signal transduction pathways are closely related to carcinogenesis, growth, recrudescence and metastasis. Phosphoinositide3-kinases (PI3Ks) are critical elements in a signal transduction pathway for cell life cycles. They play a key role in regulating and mediating the cell biological processes related to tumorigenesis, including cell proliferation, apoptosis, transcription, translation, metabolism, angiogenesis and cell cycle. Therefore, PI3K inhibitors have unique advantages in inhibiting cancer cell proliferation, inducing apoptosis and reversing cancer drug resistance, and they can be used as a single agent or in combination with other molecule targeted drugs. Targeting the key components of PI3K pathway has become one of the hotspots in anticancer drug developments. Now, dozens of PI3K signal pathway inhibitors enter clinical or preclinical trial.Compound XM002S with a benzopyran scaffold was a novel PI3K inhibitor discovered by Prof. Xinliang Mao in Soochow University, in a high-throughput virtual screening from the Maybridge library of56000compounds. XM002S can inhibit PI3K activity, decrease the synthesis of PtdIns(3,4,5)P3, block the migration of Akt to cell membrane and thus inhibit the Akt phosphorylation. XM002S exhibited potent anti-hematologic malignancy activities both in vitro and in vivo. XM002S has the following pharmacological features:1) It effectively inhibited cell growth of multiple myeloma (MM), such as H929, My5, LP1, KMS11, KMS12, KMS18, but had little effects on normal blood cell and hematopoietic stem cells;2) It notably induced MM cell apoptosis, activated caspase-3and caspase-9, and inhibited anti-apoptosis proteins Bcl-2and Mcl-1;3) XM002S was a nonselective, pan-class I PI3K inhibitor, and inhibited all four isoforms of class I PI3K with an IC50ranging from65.2to110.2μM;4) Through inhibiting the PI3K/Akt signal pathway, XM002S remarkably inhibited the Akt phosphorylation in MM cell, the cyclin D mRNA transcription and protein expression, and thus arrested the cell at the G0/G1phase;5) It had no inhibition on the mTOR. In a word, XM002S exhibits potent antitumor activity both in vitro and in vivo with low toxicity. Its antitumor mechanism is clearly elucidated. Thus, XM002S is a good hit compound targeting PI3K/Akt pathway.However, there is a chiral center in XM002S. As a chiral molecule, the biological activity of its single enantiomer has been not established. In addition, the synthetic methods for both XM002S and its chiral enantiomers have not been set up; Moreover, the structure-activity relationship of XM002S needs to be confirmed.In order to make the above questions clear, we established a new method for the synthesis of XM002S and its derivatives by the reation of3-ethoxylsalicylaldehyde and the relevant β-nitrostyrene catalyzed by the mixture of L-proline and triethylamine. Tumor cell growth inhibitory bioassay proved that the introduction of an electron-withdrawing group such as fluoro-or cyano-at the para-position of 2-phenyl was favorable for the activity, while an electron-donating group (methoxy) decreased the activity. We also prepared both enantiomers of XM002S,(R)-XM002S and (S)-XM002S, by chemical resolution strategy using (S)-(+)-α-methoxyphenylacetic acid as a chiral resolution agent. The cell growth inhibitory activities of (R)-XM002S and (S)-XM002S showed little difference, and this indicated that the chiral center in XM002S might be not important for the activity. Therefore, we synthesized two non-chiral compounds,8-ethoxyl-3-nitro-2H-chromene (20a) and6-bromo-8-ethoxyl-3-nitro-2H-chromene (20b), by removing the4-fluorophenyl at the chiral center in XM002S. Both of them showed good inhibition toward hematologic malignancy cells, especially the latter compound was better than XM002S and the relatively higher active enantiomer (R)-XM002S, and significantly inhibited the expression of Akt and its phosphorylation level, and induced cell apoptosis.In summary, novel methods for the synthesis of3-nitro-2H-chromenes and (R)-XM002S and (S)-XM002S were developed. Biological studies proved that the electronic properties of the substituents in the phenyl ring at the2-position affected the tumour cell growth inhibitory activity, but the absolute configuration of chiral center had little influences. We further simplified the structure of XM002S, and found a high potent, non-chiral compound20b. This study made a basis for further structure modification to find high potent and high selective PI3K inhibitors.