Copper-catalyzed silylation of aryl and alkenyl triflates with silylboronic esters avoiding base-mediated borylation.

Silylation of aryl and alkenyl triflates is found to occur readily with silylboronic esters as a silicon source under copper catalysis. The silyl moieties are exclusively installed into the organic frameworks through the preferential generation of a silylcopper species, wherein base-mediated direct borylation is totally suppressed. The combined use of tri-n-butylphosphine and 4,4'-diphenyl-2,2'-bipyridine as a ligand combination turned out to be indispensable for achieving the high catalytic activity.

Synthesis of Deuterated Compounds by Flow Chemistry.

Development of the efficient and practical method for the synthesis of deuterated compounds which occupies the broadest area among stable isotopes is one of the most essential issues toward the industrial advance and building a sustainable society. This review describes recent advances in deuteration reactions, where the continuous flow chemistry plays pivotal roles for the successful installation of deuterium atom into diverse organic frameworks, opening new fields of isotope-based synthetic chemistry.

[Stereocontrolled synthesis of phosphinyl dipeptide isosteres using an asymmetric center at the phosphorus atom].

Phosphinyl dipeptide isosteres (PDIs) are important compounds for the development of potent and selective inhibitors of various aspartic proteases and Zn metalloproteases. The stereochemistry of PDIs affects their biological activity. PDIs were prepared successfully using the concept of asymmetric induction from the chiral phosphorus atom of the phosphinate moiety to the neighboring carbon atom. This methodology involves diastereoselective α-alkylation and ß'-alkylation of P-chiral phosphinate derivatives, prepared through lipase-catalyzed kinetic resolution, which produces Phe-Ala type and Pro-Phe type PDIs. The synthesis of Leu-Pro type PDIs in a protected form was achieved through a cross-coupling reaction of stereodefined α-amino-H-phosphinate with alkenyl triflate, followed by diastereoselective hydrogenation of the alkene moiety.

One-pot synthesis of phenol derivatives by the novel intramolecular Alder-Rickert reaction: effects of aryl substituent at the 3-position of cyclohexenone derivatives on reactivity.

We examined In(OTf)3-catalyzed enolization and intramolecular Alder-Rickert reactions of cyclohexenone derivatives. The 3-aryl substituted cyclohexenone derivatives bearing an ethoxycarbonyl-substituted alkyne moiety could be converted into the corresponding phenols in comparatively good yield.

Synthesis of phenol derivatives from cyclohex-2-enones bearing an alkyne through Lewis acid-catalyzed enolization and intramolecular Alder-Rickert reaction.

A cationic rhodium(I) complex- or In(OTf)(3)-catalyzed synthesis of phenol derivatives from cyclohex-2-enone having an ethoxycarbonyl-substituted alkyne has been achieved. This reaction proceeds via enolization and an intramolecular Alder-Rickert reaction.

Diastereoselective synthesis of the Leu-Pro type phosphinyl dipeptide isostere.

A diastereoselective synthesis of the Leu-Pro type phosphinyl dipeptide isostere in its protected form was achieved from stereodefined α-amino-H-phosphinate. The methodology involved a cross-coupling reaction with alkenyl triflate and subsequent diastereoselective hydrogenation of the alkene moiety, which capitalized on the phosphorus chirality.

Diastereoselective synthesis of gamma-amino-delta-hydroxy-alpha,alpha-difluorophosphonates: a vehicle for structure-activity relationship studies on SMA-7, a potent sphingomyelinase inhibitor.

A highly diastereoselective synthesis of 2-amino alcohol derivatives bearing a difluoromethylphosphonothioate group at the 3-position was achieved through LiAlH(O-t-Bu)(3)-mediated reduction of the corresponding alpha-amino ketones. The phosphonothioate moiety of the product was readily converted into the corresponding phosphonate by oxidation with m-CPBA, followed by aqueous workup. The developed methods should be useful for SAR studies of SMA-7, a potent inhibitor of SMases.

Diastereoselective synthesis of alpha,beta'-disubstituted aminomethyl(2-carboxyethyl)phosphinates as phosphinyl dipeptide isosteres.

A new and efficient method has been developed for the diastereoselective synthesis of unnatural dipeptide analogues containing the metabolically stable phosphinic moiety, NH 2XaaPsi[P(O)OHCH 2]XaaOH, which mimics the transition state of tetrahedral geometry of a scissile peptide bond in hydrolysis by protease. The method is based upon stereospecific Michael addition of stereodefined alpha-aminoalkyl- H-phosphinates to acrylates and subsequent diastereoselective alkylation at the beta'-position of the resulting Michael adducts.

Antitumor studies -- part 2: structure-activity relationship study for flavin analogs including investigations on their in vitro antitumor assay and docking simulation into protein tyrosine kinase.

Various analogs of flavins, 5-deazaflavins, and flavin-5-oxides were docked into the binding site of protein tyrosine kinase pp60(c-src), and some of them were assayed for their potential antitumor and PKC (protein kinase C) inhibitory activities in vitro. The results considering SAR (structure-activity relationship) revealed that the higher binding affinities obtained include compounds with the structure modifications on the flavin or 5-deazaflavin skeleton, namely, NH(2) or Ph (phenyl-) group at the C-2 position and so on. Computationally designed compounds 4a, 6a, b, 7, 11b, c, 12, 15, and 22c exhibited good docking results suggesting that they are potentially active antitumor agents. These compounds have 1-3 phenyl moieties, which are thought to be responsible for the planar aromatic fitting or electrostatic attraction onto the groove of the binding pocket.

Antitumor studies. Part 1: design, synthesis, antitumor activity, and AutoDock study of 2-deoxo-2-phenyl-5-deazaflavins and 2-deoxo-2-phenylflavin-5-oxides as a new class of antitumor agents.

Novel 2-deoxo-2-phenyl-5-deazaflavins and 2-deoxo-2-phenylflavin-5-oxides were prepared as a new class of antitumor agents and showed significant antitumor activities against NCI-H 460, HCT 116, A 431, CCRF-HSB-2, andKB cell lines. In vivo investigation, 2-deoxo-10-methyl-2-phenyl-5-deazaflavin exhibited the effective antitumor activity against A 431 human adenocarcinoma cells transplanted subcutaneously into nude mouse. Furthermore, AutoDock study has been done by binding of the flavin analogs into PTK pp60(c-src), where a good correlation between their IC(50) and AutoDock binding free energy was exhibited. In particular, 2-deoxo-2-phenylflavin-5-oxides exhibited the highest potential binding affinity within the binding pocket of PTK.

Antitumor effects of synthetic VEGF-receptor binding antagonist, VGA1155.

Vascular endothelial growth factor (VEGF) plays key roles in tumor angiogenesis. Therefore, VEGF and its receptors are considered to be primary targets for antiangiogenic strategy during cancer chemotherapy. Our previous study reported that VGA1155, a low-molecular-weight inhibitor of the binding of VEGF, inhibited VEGF binding to KDR/Flk-1 receptor-overexpressing cells. In the present study, the antitumor effects and antimetastatic effect of VGA1155 were examined in vivo. VGA1155 suppressed the growth of human lung, breast, colon and epidermoid cancers (LC-6, HT29, MX-1, Col-1 and A431) in the nude mouse xenograft model, and pulmonary metastasis of melanoma in the spontaneous metastasis model. These results suggest that VGA1155 has antitumor effects in vivo through the inhibition of VEGF binding to its receptors.

VGA1155, a novel binding antagonist of VEGF, inhibits angiogenesis in vitro and in vivo.

The process of angiogenesis involves the formation of new blood vessels from established vasculature and is essential for progressive tumor growth and metastasis. Since vascular endothelial growth factor (VEGF) plays a pivotal role in tumor angiogenesis, it is reasonable to expect that antagonizing VEGF binding to its receptor may be effective in cancer therapy. Our previous study found that a novel low molecular weight compound, VGA1155, inhibited binding between radioisotope-labelled VEGF and cells overexpressing its two receptors, Flt-1 and KDR/Flk-1, that is, NIH3T3-Flt-1 and NIH3T3-KDR, respectively. In the present study, we investigated the anti-angiogenic effects of VGA1155 based on VEGF inhibition. VGA1155 inhibited VEGF-induced DNA synthesis of human umbilical vein endothelial cells (HUVEC) and human retinal endothelial cells (HREC) in a concentration-dependent manner. VGA1155 also inhibited VEGF-induced tube formation of HUVEC in vitro and tumor angiogenesis toward B16-BL6 melanoma after orthotopic implantation into the skin of the back. On the other hand, VGA 1155 did not affect the proliferation of human epidermoid carcinoma (KB) cells and mouse mammary carcinoma (MM2) cells. It also had no effect on the activity of several cytosolic kinases such as p55fyn and p56lck. These findings suggest that VGA1155 inhibits endothelial cell growth and angiogenesis by inhibiting VEGF function but not non-specific cytotoxicity. VGA1155 thus exhibits promise as an antiangiogenic or anti-tumor agent with fewer side-effects.

A novel low molecular weight VEGF receptor-binding antagonist, VGA1102, inhibits the function of VEGF and in vivo tumor growth.

Vascular endothelial cell growth factor (VEGF) plays an important role in the processes of angiogenesis. Angiogenesis appears to be essential for the growth of solid tumors and their metastasis. VEGF plays a principal role in tumor angiogenesis. To identify a compound that inhibits the binding of VEGF to its receptor, we used a high-throughput screening method and found that oxydibenzoic acid derivatives inhibited VEGF binding to its receptors. Among the active compounds, 5-[3-[4-(octadecyloxy)phenyl]propionylamino]-2,4'-oxydibenzoic acid (VGA1102) was selected based on its potent binding inhibitory activity. VGA1102 inhibited [(125)I]VEGF binding to both of two VEGF receptor-transfected cell lines, NIH-Flt-1 and NIH-KDR/Flk-1, in a concentration-dependent manner, with IC(50) values of 0.66+/-0.07 and 0.61+/-0.16 micro M, respectively. VGA1102 (10 micro M) exhibited inhibitory activity against VEGF-induced receptor autophosphorylation. VGA1102 also inhibited VEGF-induced growth of rat liver sinusoidal endothelial cells (IC(50)=0.89+/-0.16 micro M) as well as VEGF-induced tube formation of HUVEC in vitro. VGA1102 reduced intradermal VEGF-induced vascular permeability in guinea pigs. Treatment with VGA1102 (50 mg/kg, i.p., days 0-20) significantly increased the lifespan of MM2-bearing mice with an increase in lifespan of >195.8%, and all such mice were long-term survivors on day 71. Furthermore, VGA1102 (50 mg/kg, i.p.) administered daily suppressed the growth of nude mice transplanted with LC-6 human non-small-cell lung cancer. These results suggest that VGA1102 inhibits VEGF function resulting in inhibition of tumor angiogenesis, which led to suppression of growth of human tumors transplanted into nude mice.

A novel low molecular weight antagonist of vascular endothelial growth factor receptor binding: VGA1155.

Vascular endothelial growth factor (VEGF) plays a pivotal role in the processes of angiogenesis, which is essential for the growth of solid tumors and their metastasis. Because VEGF is a critical factor in tumor survival, inhibiting VEGF would provide significant benefits in tumor therapy. To identify a compound that inhibits the binding of VEGF to its receptor, we used a high throughput screening method, finding that small molecular compounds inhibited VEGF binding. Among active compounds, 5-[N-methyl-N-(4-octadecyloxyphenyl)acetyl]amino-2-methylthiobenzoic acid (VGA1155) was selected for its potent inhibition of binding. VGA1155 inhibited [(125)I] VEGF binding to two cell lines, NIH3T3-fms-like tyrosine kinase-1 (VEGF receptor 1 transfected) cells and NIH3T3-kinase insert domain containing receptor/fetal liver kinase-1 (KDR/Flk-1; VEGF receptor 2 transfected), in a concentration-dependent manner. VGA1155 did not inhibit the binding of several other growth factors or cytokines to their receptors. Based on the results of surface plasmon resonance analysis using Biacore S51 system, it appears that this binding inhibitory property may be based on the association of VGA1155 with VEGF receptor 2 (KDR/Flk-1). Further, the interference in VEGF binding by VGA1155 in turn induces the inhibition of VEGF-induced KDR/Flk-1 autophosphorylation. VGA1155 also reduced intradermal VEGF-induced vascular permeability in guinea pigs. These findings indicate that VGA1155 inhibits not only VEGF binding to its receptors through association with KDR/Flk-1 but also VEGF function in vivo. These VGA1155 activities may provide a useful basis for the development of antiangiogenic and antitumor agents.

Establishment and characterization of a mouse FM3A cell mutant resistant to topoisomerase II-inhibitor NC-190.

We established an NC-190-resistant cell line, FM/NC-R, from the murine mammary carcinoma cell line FM3A and examined some of its characteristics. FM/NC-R cells were prepared by mutagen treatment followed by exposure to NC-190 in the culture medium. FM/NC-R cells were 76.5 times more resistant against NC-190 than FM3A cells as measured by their growth in vitro. FM/NC-R cells also showed cross-resistance to etoposide with NC-190. Neither NC-190 nor etoposide increased the lifespan of FM/NC-R-bearing mice at doses that prolonged the lifespan of FM3A-bearing mice more than four times. This resistance was not due to the change in the concentration of NC-190 in the cells, and there was no change in the expression of P-glycoprotein, a drug efflux pump in the cells. NC-190 and etoposide are inhibitors of DNA topoisomerase II, but there was no difference in cellular content of DNA topoisomerase II between the two cell lines as determined by Western blot analysis. The stabilization of DNA-DNA topoisomerase II cleavable complexes induced by NC-190 was lost in FM/NC-R cells. It was found that Gly881, which is located in the ATP binding site, was replaced by Arg in topoisomerase IIalpha of FM/NC-R cells. These results indicate that the NC-190-resistant cell line FM/NC-R contains a mutated DNA topoisomerase IIalpha.

The topoisomerase II-inhibitor NC-190 reduces the level of thymidine kinase mRNA in murine tumor cells.

The novel antitumor compound NC-190 strongly inhibited the growth of FM3A cells with an IC50 of 0.019 microg/ml (0.042 microM) when cultured with NC-190 for 48 h. NC-190 potently suppressed DNA synthesis, with 90% inhibition observed at 0.1 microg/ml of NC-190. RNA and protein syntheses were also suppressed under the same conditions, but to a lesser extent. We then measured the cellular enzymatic activities of DNA polymerase alpha, RNA polymerase, thymidine kinase, thymidylate synthase and Leu-tRNA synthetase of FM3A cells cultured with or without NC-190. Of these 5 enzymes, the activity of thymidine kinase was most strongly suppressed by NC-190, by 77%. Although NC-190 did not directly inhibit the activitiy of thymidine kinase in a cell-free system, expression of mRNA of thymidine kinase was suppressed by 75% in NC-190-treated cells. These results indicate that NC-190 can suppress the expression of the gene for thymidine kinase and the inhibition of thymidine kinase contributes to the inhibition of cell growth by NC-190 together with the inhibition of topoisomerase II.