Impact of pyrrolidine-bispyrrole DNA minor groove binding agents and chirality on global proteomic profile in Escherichia Coli.

BACKGROUND: There is great interest in the design of small molecules that selectively target minor grooves of duplex DNA for controlling specific gene expression implicated in a disease. The design of chiral small molecules for rational drug design has attracted increasing attention due to the chirality of DNA. Yet, there is limited research on the chirality effect of minor groove binders on DNA interaction, especially at the protein expression level. This paper is an attempt to illustrate that DNA binding affinity might not provide a full picture on the biological activities. Drug interacting at the genomic level can be translated to the proteomic level. Here we have illustrated that although the chiral bispyrrole-pyrrolidine-oligoamides, PySSPy and PyRSPy, showed low binding affinity to DNA, their influence at the proteomic level is significant. More importantly, the chirality also plays a role. Two-dimensional proteomic profile to identify the differentially expressed protein in Escherichia coli DH5α (E coli DH5α) were investigated. RESULTS: E coli DH5α incubated with the chiral PySSPy and PyRSPy, diastereomeric at the pyrrolidine ring, showed differential expression of eighteen proteins as observed through two dimensional proteomic profiling. These eighteen proteins identified by MALDI_TOF/TOF MS include antioxidant defense, DNA protection, protein synthesis, chaperone, and stress response proteins. No statistically significant toxicity was observed at the tested drug concentrations as measured via MTT assay. CONCLUSION: The current results showed that the chiral PySSPy and PyRSPy impact on the proteomic profiling of E coli DH5α, implicating the importance of drug chirality on biological activities at the molecular level.

Synthesis of directly linked diazine isosteres of pyrrole-polyamide that photochemically cleave DNA.

A distamycin model containing an isosteric diazine linked pyrrole has been designed and synthesized. The key steps of the synthesis involved the successful diazotization of the 4-amino-pyrrole derivatives to give the diazomium salts, which undergo coupling reactions with N-methylpyrrole to yield the directly linked diazine compounds. The amide isosteric-diazine pyrrole I demonstrated photo-induced DNA damage upon iradiation with UV light (365 nm). Spectrophotometric and mass spectrometric identification suggest that the azo-linkage in I did not dissociate during irradiation. Moreover, compound I produced DNase I footprints with the HexB DNA fragment at AT sites, as well as some other mixed sequences (5'-ATGTCG-3'), indicative of the additional role of the diazine-linkage for interaction at the duplex DNA.

Diastereoselective synthesis of a highly functionalized angularly substituted cis-perhydroisoquinoline-3,6-dione via organoiron.

Nitrile addition to cyclohexadienyium-Fe(CO)(3) perchlorate salt provides an efficient entry into the angularly substituted cis-fused perhydroisoquinoline ring system. The key steps in the assembly of the angularly substituted cis-octahydroisoquinoline ring are the transformation of the nitrile to an N-(benzylmethylencie)amino group and a diastereoselective intramolecular Michael reaction to form the bicyclic ring.

Orientational packing of a confined discotic mesogen in the columnar phase.

The stacking of discotic molecules (hexakis(alkoxy)diquinoxalino[2,3-a:2',3'-c]phenazines) in the columnar phase sandwiched between two flat glass substrates has been studied. The surface free energy of the substrates, measured by means of sessile drop technique, is found to have significant influence on the way that the discotic molecules anchor on the surface, and a steady thermal state of the system is crucial for a homogenous orientation of the discotic columns. On a surface of high free energy, the discotic molecules anchor with their disc-face toward the surface. A decrease in the surface free energy of the substrate causes the discotic columns to tilt away from the normal of the substrate.

Long-Range Self-Assembly of an Electron-Deficient Hexaazatrinaphthylene with Out-of-Plane Substituents.

The unprecedented time-dependent long-range supramol-ecular assembly of electron-deficient hexaazatrinaphthylene (HATN) core based on peripheral crowding with three out-of-plane cyclic ketals is reported. The single-crystal X-ray structure of the diethyl derivative provided detailed information as to how four molecules in a repeating unit were packed in order to avoid steric crowding of the out-of-plane cyclic ketal side chain, providing locking and fastening for stabilizing the self-assembled structure. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) did not instantaneously show any phase transition upon the cooling process. To our surprise, POM images showed a nucleation of spherulite up to 100 µm after 24 hour later. X-ray diffraction data further confirmed that these soft crystal formed a hexagonal-like crystal. The long-range self-assembly of the new material showed a slight red shift in the UV-vis absorption spectra and further substantiated by computational method.

Superstructure manipulation and electronic measurement of monolayers comprising discotic liquid crystals with intrinsic dipole moment using STM/STS.

In this work, we studied the discotic liquid crystals (DLCs) of dibenzo[a,c]phenazine at the liquid-solid interface using scanning tunnelling microscopy/spectroscopy, by which we show how to tailor the DLC assemblies and in turn their electron-transfer efficiency. This study presents an alternative method for phase control and electronic measurements for DLCs, especially at the microscopic level.

Synthesis and mesomorphic behavior of a donor-acceptor-type hexaazatriphenylene.

[structure: see text] A new donor-acceptor, 1,4,5,8,9,12-hexaazatriphenylene HATCNOR(n), is described. The synthesis of HATCNOR1 and HATCNOR6 is achieved by the regioselective displacement of 1,4,5,8,9,12-hexaazatriphenylene hexacarbonitrile (HATCN) with an alkoxy group. The X-ray analysis revealed self-assembly of HATCNOR1 in the solid state. HATCNOR6 is the new difunctionalized hexaazatriphenylene discotic liquid crystal.

Minor-Groove Binding Agents: Rational Design of Carboxamide Bond Isosteres.

Distamycin and netropsin analogues have been designed for targeting specific sequences in DNA. Numerous reviews have been centered on the replacement of N-methylpyrrole with heteroaromatic rings in order to induce better fitting to improve the binding efficiency and the introduction of additional interactions for recognition of GC base pairs at the minor groove of DNA. Most of these designed analogs retained the use of carboxamide-bond for interconnecting the heteroaromatic rings. Computer simulations of netropsin and distamycin has pinpointed the advantages of designing isosteres of the carboxamide-bond for amplifying or attenuating particular interactions to DNA, but have been less studied. The key challenges that must be overcome to realize this goal are the development of feasible synthetic methodologies. This review examined in detail for the first time the electronic, structural, and conformational attributes of the various carboxamide isosteres: (i) neutral isostere-alkenyl and alkyl, (ii) hydrogen donating isostere-urea and carbonylurea, and (iii) hydrogen acceptor isosteres-diazene and diketone. In particular, the ability of these isosteres to participate in non-covalent interactions by tuning the shape and hydrogen bonding to the floor of the minor groove is compared with that of the carboxamide bond. We hope this review will encourage the development of a library of modified isosteres of the carboxamide bond which target DNA with excellent sequence specificity, stronger binding affinity and exhibit improved biological properties. Another goal is to develop synthetic methodolgies for the ready synthesis of poly-isosteric bond used in mimicking of the poly-carboxamide bond for DNA minor groove binding agents, the area in which progress has been slow.

The regioselective homocoupling of meta-hydroxypyridines with hypervalent iodine(III).

The C - H homocoupling of meta-hydroxypyridines with phenyliodine(III) diacetate (PIDA) was carried out in dichloromethane at room temperature in the presence of cesium carbonate. The coupling reaction is highly regioselective with respect to the hydroxy group at the pyridine ring. Comparative control experiments with meta-alkoxypyridine suggest that the meta-hydroxy group at the pyridine ring plays a key role during the homocoupling reaction.

Tricarbonylcyclohexadienyliumiron Complexes in the Synthesis of 2-Azaspiro[5.5]undecane System with Tunable Amide.

Excellent regio- and stereoselectivity during nitrile addition to dienylium-Fe(CO)(3) can be achieved with perchlorate salts, allowing the preparation of the 1-oxo- and 3-oxo-2-azaspiro[5.5]undecane ring systems. The phthalimide complex 2 was prepared in high yield by Mitsunobo reaction.

Novel Rearrangements of 2,3-Dimercapto-1-propanol Derivatives: Formation of Dialkyl Sulfide, Dialkyl Disulfide, and 1,2,3-Tris(alkylthio)propane.

The base alkylation of 2,3-dimercapto-1-propanol with alkyl halides leads in good yield to 2,3-bis(alkylthio)-1-propanol and dialkyl sulfide. The reaction of 2,3-bis(alkylthio)-1-propanol with catalytic concentrated sulfuric acid proceeds with rearrangement to give 1,2,3-tris(alkylthio)propane and dialkyl disulfide. The rearrangement reaction takes place through a common intermediate thiaranium intermediate 8.

Syntheses of C(18) dibenzocyclooctadiene lignan derivatives as anti-HBsAg and anti-HBeAg agents.

(+)-Gomisin K(3) (1) and kadsurarin (2) were isolated from Schizandra arisanensis and Kadsura matsudai, respectively, and a series of C(18) dibenzocyclooctadiene lignan analogues (5-20) derived from 1 and 2 were synthesized. Esterified derivatives of 1 and 2 were evaluated for inhibitory activity against human type B hepatitis with surface antigen (HBsAg) and e antigen (HBeAg). Most of the analogues (5-8, 10, 12-13) derived from 1 exhibited higher anti-HBsAg effects and lower toxicity, and 6, 7, 8 and 12 also showed higher anti-HBeAg activity. Among these active C(18) dibenzocyclooctadiene lignan analogues, the lignan with a but-3-enoyl group (6) exhibited the most active inhibition.

Antihepatitis activity (anti-HBsAg and anti-HBeAg) of C19 homolignans and six novel C18 dibenzocyclooctadiene lignans from Kadsura japonica.

Bioassay-directed fractionation of the EtOAc extract of Kadsura japonica has led to the isolation of six new C18 dibenzocyclooctadiene lignans, schizanrins I, J, K, L, M, N, along with four known C19 homolignans, taiwanschirins A, B, C, and heteroclitin F. The elucidations of the new structures were based on spectral analysis. Bioassay evaluation against human type B hepatitis revealed that taiwanschirins A and B showed strong activity for anti-HBsAg and a medium effect for anti-HBeAg at 25 microg/mL (12.9 and 11.9 microM for taiwanschirins A and B, respectively).

In situ synthesis of hexakis(alkoxy)diquinoxalino[2,3-a:2',3'-c]phenazines: mesogenic phase transition of the electron-deficient discotic compounds.

2,3,8,9,14,15-Hexakis(alkoxy)diquinoxalino[2,3-a:2',3'-c]phenazines with alkyl side chains varying from 6 to 12 carbon atoms were readily synthesized by the condensation of hexaketocyclohexane with the respective 1,2-bisalkoxy-4,5-diaminobenzene. Polarization microscopy and DSC studies showed all these compounds to exhibit a very wide mesophase range of over 150 degrees C. An interesting D(hd) to D(rd) transition was observed for the octyl derivative 3b, as determined by X-ray diffraction measurements. The hexyl derivative showed three reduction potentials, suggesting that the HATN core maintained its electron-deficient characteristic and considered suitable as an n-doped discotic-liquid crystalline material. Incorporation of six alkoxy chains did not override the electron deficiency of the HATN core.

The anti-HBsAg (human type B hepatitis, surface antigen) and anti-HBeAg (human type B hepatitis, e antigen) C18 dibenzocyclooctadiene lignans from Kadsura matsudai and Schizandra arisanensis.

The C(18) dibenzocyclooctadiene lignans including three novel schizanrin F (1), G (2), H (3), along with the known kadsurarin (4), were isolated from Kadsura matsudai. A new C(19) homolignan named schiarisanrin E (5), together with the known C(18) lignans, gomisin B (6), G (7) and (+)-gomisin K(3) (8) were obtained from Schizandra arisanensis. Gomisin B, G and (+)-gomisin K(3) showed moderate to strong activity for antihepatitis in anti-HBsAg (human type B hepatitis, surface antigen) and/or anti-HBeAg (human type B hepatitis, e antigen) tests. The structural elucidations of new compounds 1-3 and 5 were based on two-dimensional (2D) NMR techniques including COSY, HMQC, HMBC, NOESY and CD spectra. Preliminary structure-activity relationship studies for these isolated lignans are also discussed.

Two novel sesquiterpene lactones, cytotoxic vernolide-A and -B, from Vernonia cinerea.

Bioassay-directed fractionation of an ethanolic extract of stems of Vernonia cinerea has resulted in the isolation of two novel sesquiterpene lactones, vernolide-A and -B. Their structures were elucidated on the basis of spectroscopic analysis. Biological evaluation showed that vernolide-A demonstrated potent cytotoxicity against human KB, DLD-1, NCI-661, and Hela tumor cell lines (ED(50)=0.02, 0.05, 0.53, 0.04 microg/ml for KB, DLD-1, NCI-661, and Hela, respectively); vernolide-B had marginal cytoxicity (ED(50)=3.78, 5.88, 6.42 microg/ml for KB, NCI-661, and Hela, respectively).