Folate antagonists. 5. Antimalarial and antibacterial effects of 2,4-diamino-6-(aryloxy and aralkoxy)quinazoline antimetabolites

2 Various4-diamino-6-(phenoxy, naphthyloxy, and phenalkoxy)quinazolines (VIII, XIV) were synthesized for antimalarial and antibacterial evaluation. Treatment of the anion of the requisite phenol or naphthol with 5-chloro-2-nitrobenzonitrile (V) gave the corresponding 2-nitro-5-(phenoxy and naphthyloxy)benzonitriles (VI) (33–78%). Alternatively, alkylation of 5-hydroxy-2-nitrobenzaldehyde (IX) with the appropriate phenalkyl halide afforded the 2-nitro-5-(phenalkoxy)benzaldehydes (X) (27–62%), which were converted to the 2-nitro-5-(phenalkoxy)benzonitriles (XII) via the intermediate oximes XI (62–87% overall). Reduction of the 2-nitrobenzonitriles (VI, XII) with stannous chloride-hydrochloric acid provided the corresponding 2-amino-5-(phenoxy, naphthyloxy, and phenalkoxy)benzonitriles (VII, XIII) (30–83%), which upon cyclization with chloroformamidine hydrochloride gave the 2,4-diaminoquinazolines VIII and XIV (12–85%). Against Plasmodium berghei in mice, eleven compounds were active orally at doses ranging from 6.3 to 174 mg./kg./day for 6 days, while seven substances displayed activity subcutaneously following single doses of 40–640 mg./kg. Fifteen compounds exhibited in vitro antibacterial activity against Streptococcus faecalis (MGH-2), normal (UC-76) and drug-resistant (S18713) Staphylococcus aureus, Escherichia coli (Vogel), and Shigella sonnei (C-10) with MIC's ranging from < 0.25 to 20 μg./ml. (gradient plate). Data on the inhibitory effects of representative compounds against Streptococcus faecalis R (S. faecium var. durans), S. faecalis A (amino-pterin, methotrexate-resistant), and Lactobacillus plantarum are presented, and overall structure-activity relationships are discussed.     

Metallodrugs are unique: opportunities and challenges of discovery and development

Metals play vital roles in nutrients and medicines and provide chemical functionalities that are not accessible to purely organic compounds. At least 10 metals are essential for human life and about 46 other non-essential metals (including radionuclides) are also used in drug therapies and diagnostic agents. These include platinum drugs (in 50% of cancer chemotherapies), lithium (bipolar disorders), silver (antimicrobials), and bismuth (broad-spectrum antibiotics). While the quest for novel and better drugs is now as urgent as ever, drug discovery and development pipelines established for organic drugs and based on target identification and high-throughput screening of compound libraries are less effective when applied to metallodrugs. Metallodrugs are often prodrugs which undergo activation by ligand substitution or redox reactions, and are multi-targeting, all of which need to be considered when establishing structure–activity relationships. We focus on early-stage in vitro drug discovery, highlighting the challenges of evaluating anticancer, antimicrobial and antiviral metallo-pharmacophores in cultured cells, and identifying their targets. We highlight advances in the application of metal-specific techniques that can assist the preclinical development, including synchrotron X-ray spectro(micro)scopy, luminescence, and mass spectrometry-based methods, combined with proteomic and genomic (metallomic) approaches. A deeper understanding of the behavior of metals and metallodrugs in biological systems is not only key to the design of novel agents with unique mechanisms of action, but also to new understanding of clinically-established drugs.

The vital roles of metals in nutrients and medicines are not accessible to purely organic compounds.     

Interfacial glass transition profiles in ultrathin, spin cast polymer films

Interfacial glass transition temperature (T(g)) profiles in spin cast, ultrathin films of polystyrene and derivatives were investigated using shear-modulated scanning force microscopy. The transitions were measured as a function of film thickness (delta), molecular weight, and crosslinking density. The T(g)(delta) profiles were nonmonotonic and exhibited two regimes: (a) a sublayer extending about 10 nm from the substrate, with T(g) values lowered up to approximately 10 degrees C below the bulk value, and (b) an intermediate regime extending over 200 nm beyond the sublayer, with T(g) values exceeding the bulk value by up to 10 degrees C. Increasing the molecular weight was found to shift the T(g)(delta) profiles further from the substrate interface, on the order of 10 nm/kDa. Crosslinking the precast films elevated the absolute T(g) values, but had no effect on the spatial length scale of the T(g)(delta) profiles. These results are explained in the context of film preparation history and its influence on molecular mobility. Specifically, the observed rheological anisotropy is interpreted based on the combined effects of shear-induced structuring and thermally activated interdiffusion.     

Investigation of the scope of a [3+2] cycloaddition approach to isoxazole boronic esters

The [3+2] cycloaddition reaction of nitrile oxides and alkynylboronates provides direct access to a wide variety of isoxazole boronic esters. Specifically, this technique has been employed to generate trisubstituted isoxazole 4-boronates and disubstituted isoxazoles where the boronic ester moiety can be installed at C-4 or C-5 with high levels of regiocontrol. The application of this methodology in the synthesis of non-steroidal antiinflammatory agents is also described.     

Spectrometric and 2D NMR Studies on the Complexation of Chlorophenols with Cyclodextrins

The formation and structure of inclusion complexes of - and-cyclodextrins with 2-chlorophenol (2CP), 3-chlorophenol (3CP),4-chlorophenol (4CP), 2,4-dichlorophenol (24DCP), 2,6-dichlorophenol(26DCP) and 3,4-dichlorophenol (34DCP) have been studied by UV-VIS and¹H NMR spectroscopy. Both cyclodextrins were found to form 1:1inclusion complexes. Bindingconstants estimated from titration studies revealed that the stability of the complexes was highly dependent on the structure and polarity of the chlorophenol and on the cyclodextrin used. In general, weaker binding constants were observed for a given chlorophenol with -cyclodextrin than with-cyclodextrin. The weakest binding constants (K_{b < 200} M^-1) were obtained for the ortho-substituted chlorophenols (2CP and 26DCP) and the largest binding constants were obtained between para-chlorophenols (4CP, 24DCP and 34DCP) and-cyclodextrin. 2D-TROESY studies of chlorophenol-cyclodextrincomplexes in D₂O provided insight into the structure of the complexes.     

CORRELATION OF UVC AND UVB CYTOTOXICITY WITH THE INDUCTION OF SPECIFIC PHOTOPRODUCTS IN T-LYMPHOCYTES AND FIBROBLASTS FROM NORMAL HUMAN DONORS

Abstract— By using specific monoclonal antibodies in situ and a computer-assisted image analysis system we have determined the relative induction of cyclobutane dimers, (6–4) photoproducts and Dewar isomers in human mononuclear cells and fibroblasts following irradiation with UVC, broad-spectrum UVB and narrow-spectrum UVB. The lamps produced these lesions in different proportions, with broad-spectrum UVB inducing a greater combined yield of (6–4) photoproducts and Dewar isomers per cyclobutane dimer than UVC or narrow-spectrum UVB. The relative induction ratios of (6–4) photoproducts compared to cyclobutane dimers were 0.15, 0.21 and 0.10 following irradiation with UVC, broad- or narrow-spectrum UVB, respectively. Although Dewar isomers were induced by UVC, their relative rate of formation compared to cyclobutane dimers was significantly greater after irradiation with either broad-spectrum or narrow-spectrum UVB. These values were 0.001, 0.07 and 0.07, respectively. With each lamp source, we have determined the survival of normal human T-lymphocytes and fibroblasts at fiuences, which induce equivalent yields of cyclobutane dimers, (6–4) photoproducts or (6–4) photoproducts plus Dewar isomers. Killing of fibroblasts appears to be associated with (6–4) photoproduct formation, whereas killing of T-lymphocytes seems to be mediated by combined (6–4) plus Dewar yields. These results emphasize the need to study the biological effects of UVB because cellular responses may be different from those following UVC irradiation.     

Application of aza-transfer to organic compounds : Reactions between heterocyclic diazo compounds and hydrazines

Aza-transfer reactions between heterocyclic hydrazines and diazonium salts or between heterocyclic diazo compounds and substituted hydrazines have been investigated. The reaction proceeds via intermediate tetrazenes and labelled compounds have been used to elucidate the reaction mechanism.     

Arsenosugar identification in seaweed extracts using high-performance liquid chromatography/electrospray ion trap mass spectrometry

The development of analytical techniques suitable for providing structural information on a wide range of elemental species is a growing necessity. For arsenic speciation a variety of mass spectrometric techniques, mainly inductively coupled plasma mass spectrometry (ICP-MS) and electrospray tandem mass spectrometry (ES-MS/MS) coupled on-line with high-performance liquid chromatography (HPLC), are in use. In this paper we report the identification of arsenic species present in samples of marine origin (seaweed extracts) using ES ion trap mass spectrometry (IT) multistage mass spectrometry (MS(n)). Both reversed-phase and anion-exchange HPLC have been coupled on-line to ES-ITMS. Product ion scans with multiple stages of tandem MS (MS(n); n=2-4) were used to acquire diagnostic data for each arsenosugar. The spectra contain structurally characteristic fragment ions for each of the arsenosugars examined. In addition it was observed that upon successive stages of collision-induced dissociation (CID) a common product ion (m/z 237) was formed from all four arsenosugars examined. This product ion has the potential to be used as an indicator for the presence of dimethylated arsenosugars (dimethylarsinoylribosides). The HPLC/ES-ITMS(n) method developed allows the sensitive identification of arsenosugars present in crude seaweed extracts without the need for extended sample preparation. In fact, sample preparation requirements are identical to those typically employed for HPLC/ICP-MS analysis. Additionally, the resulting product ions are structurally diagnostic of the arsenosugars examined, and tandem mass spectra are reproducible and correspond well to those obtained using other low-energy CID techniques. As a result, the HPLC/ES-ITMS(n) approach minimises the potential for arsenic species misidentification and has great potential as a means of overcoming the need for characterised standards.     

Nonlocal density functional calculation of gas phase heats of formation

A general procedure is presented for computing the gas phase heats of formation of a wide variety of organic compounds. ΔE for the formation of the molecule from its elements at 0 K is obtained from density functional calculations (Gaussian 92/DFT) for optimized geometries. This result is converted to ΔH at 298 K by assuming ideal behavior and adding the translational, rotational, and vibrational energies. Additive correction terms corresponding to the various coordination states of the carbons, nitrogens, and oxygens were developed using a database of 54 compounds. The experimental ΔH values of these compounds are then reproduced with an average absolute error of 3 kcal/mol and a standard deviation of 4 kcal/mol. For a group of 10 test cases that were not part of the database, the average absolute error is 3.5 kcal/mol and the standard deviation is 4.1 kcal/mol. © 1995 by John Wiley & Sons, Inc.