Synthesis, 13C NMR spectrum and crystal structure of 10-Phenylpyrido[3,2-b][1,4]benzothiazine 5-Oxide

The compound 10-phenylpyrido[3,2-b][1,4]benzothiazine 5-oxide, 1 , has been obtained in nearly quantitative yield oxidation of 10-phenylpyrido[3,2-b][1,4]benzothiazine with oxygen in dioxane solution. The ¹³C nmr chemical shift assignments of 1 are reported. Its structure has been determined by X-ray single crystal methods. The crystals of 1 are monoclinic, space group P2₁/n. There are four molecules in a unit-cell of dimensions a = 12.347(3), b = 12.947(3), c = 8.987(1)Å, β = 106.73(1)° and V = 1375.8(5) ų. The central ring is in a boat conformation and the sulfoxide oxygen atom occupies the axial position. The folding angle between the planes of the pyrido and the benzo planes is 161.55(9)°.     

The crystal structure of 3′-methoxy-5-phenyl-5,10-dihydrophenarsazine,C19H16AsNO

The crystal structure of 3′-methoxy-5-phenyl-5,10-dihydrophenarsazine, C₁₉H₁₆AsNO has been determined by the single crystal x-ray diffraction method. The crystals are monoclinic with a = 15.305(6), b = 5.809(2), c = 17.595(6)Å, β = 92.92(2)°, V = 1562.3(1.0ų, space group P2,/n, Z = 4 and d_calc = 1.485g cm⁻³. An automatic diffractometer with graphite monochromatized MoKα radiation was used to obtain 1480 observed reflection with I > 3σ(I) at 2θ < 50°. Final R = 0.040 and wR = 0.032. The tricyclic ring is folded with the central ring in a flattened boat conformation. The folding angle between the least-squares planes of the two benzo rings is 164.6(2)°. The 3′-methoxyphenyl group is in a boat-axial conformation with respect to the central ring.     

Diastereoselectivity of a [3+2]Annulation. On the Question of a Dipole Effect on Diastereoselectivity of Olefin Addition

The stereochemistry of addition to γ-alkoxy-α,β-unsaturated carbonyl systems is examined in the context of a palladium catalyzed cycloaddition.     

Synthesis of new potentially bioactive bicyclic 2-pyridones

Three convenient methods of reduction of the nitro group of 5-nitroimidazoles and 5-nitrothiazole that bear a diethylmethylene malonate group in an ortho-like position with respect to the nitro group and cyclization of the resulting amino derivatives are reported. These reactions afforded the target bicyclic 2-pyridones in good to excellent yields.     

Crystal structure determination of 10-trifluoroacetylphenothiazine

The structure of the title compound has been determined by single crystal X-ray methods. The crystals are monoclinic, space group P2₁/n with four molecules in a cell of dimensions a = 14.365(4), b = 5.942 (2), c = 17.359(3) Å, β = 119.88(2)° and V = 1298.0(6) Å. The structure has been refined by full-matrix least-squares to R = 0.043 using 1650 observed reflections. This study shows that the folding angle between the two benzo planes is 131.8(1)°, one of the smallest values observed in phenothiazine derivatives. Also, the trifluoroacetyl group is perpendicular to the plane bisecting the tricyclic ring, in contrast to most 10-aryl-substituted phenothiazines where the substituent is approximately parallel to the plane bisecting the tricyclic ring.     

SUBCELLULAR LOCALIZATION OF AND PHOTOSENSITIZATION BY PROTOPORPHYRIN IX IN HUMAN KERATINOCYTES AND FIBROBLASTS CULTIVATED WITH 5-AMINOLEVULINIC ACID

Abstract— The subcellular localization of protoporphyrin (PP) has been studied by microspectrofluo-rometric techniques in NCTC 2544 keratinocytes incubated with 5-aminolevulinic acid (ALA) for times up to 42 h. Whereas the plasma membrane shows strong staining, fluorescent spots are observed within the cytoplasm especially in the perinuclear region. Although the topographic pattern of the PP distribution does not change much with the incubation time with ALA, the fluorescence spectra suggest that the PP microenvironments are quite different at short and long incubation times. Addition of 18 uJW desferoxamine almost doubles the ALA-induced PP concentration. Colocalization experiments with rhodamine 123, a mitochondrial probe, and lucifer yellow (LY) or neutral red (NR), two lysosome probes, demonstrate that at least some of these spots are of lysosomal origin. Study of the time evolution of the NR fluorescence under irradiation with visible light in the presence and absence of ALA demonstrates that lysosomes are damaged in cells that have synthesized PP. No PP fluorescence can be detected in mitochondria after incubation with ALA. However, photosensitization of mitochondria occurs under irradiation with visible light. Very little formation of lipofuscins by photosensitization with exogenous PP or ALA-induced PP is observed with the NCTC 2544 keratinocytes, as compared to normal human fibroblasts.     

In vitro fluorescence, toxicity and phototoxicity induced by delta-aminolevulinic acid (ALA) or ALA-esters

Synthesis of delta-aminolevulinic acid (ALA) derivatives is a promising way to improve the therapeutic properties of ALA, particularly cell uptake or homogeneity of protoporphyrin IX (PpIX) synthesis. The fluorescence emission kinetics and phototoxic properties of ALA-n-pentyl ester (E1) and R,S-ALA-2-(hydroxymethyl) tetrahydrofuranyl ester (E2) were compared with those of ALA and assessed on C6 glioma cells. ALA (100 micrograms/mL), E1 and E2 (10 micrograms/mL) induced similar PpIX-fluorescence kinetics (maximum between 5 and 7 h incubation), fluorescence being limited to the cytoplasm. The 50% lethal dose occurred after 6 h with 45, 4 and 8 micrograms/mL of ALA, E1 and E2, respectively. ALA, E1 and E2 induced no dark toxicity when drugs were removed after 5 min of incubation. However, light (25 J/cm2) applied 6 h after 5 min incubation with 168 micrograms/mL of each compound induced 85% survival with ALA, 27% with E1 and 41% with E2. Increasing the incubation time with ALA, E1 and E2 before washing increased the phototoxicity, but E1 and E2 remained more efficient than ALA, regardless of incubation time. ALA-esters were more efficient than ALA in inducing phototoxicity after short incubation times, probably through an increase of the amount of PpIX synthesized by C6 cells.     

Structure activity relationships of new inhibitors of mammalian 2,3-oxidosqualene cyclase designed from isoquinoline derivatives

We have designed more potent inhibitors from the previously reported LF 05-0038, a 6-isoquinolinol based inhibitor of 2,3-oxidosqualene cyclase (IC50: 1.1 microM). Replacement of the 3-OH group by various 3-substituted amino groups, and modification of the alkyl chain borne by the endocyclic nitrogen led to inhibitors with IC50 in the range of 0.15 to 1 microM. In a second step, opening of the bicyclic ring system afforded the corresponding aminoalkylpiperidines which were slightly more potent. Finally, introduction of suitable aromatic containing moieties on the piperidine nitrogen yielded very potent inhibitors such as 20x (IC50 = 18 nM) easy to synthesize and achiral. The recent availability of the crystal structure of squalene-hopene cyclase allowed us to construct a three-dimensional (3D) model of the related 2,3-oxidosqualene cyclase (OSC) which was tentatively used to describe the possible mode of binding of our compounds and which can be useful for designing new inhibitors.     

Phototoxicity of protoporphyrin IX, diarginine diprotoporphyrinate and N,N-diphenylalanyl protoporphyrin toward human fibroblasts and keratinocytes in vitro: effect of 5-methoxypsoralen

The phototoxicity of two new porphyrin photosensitizers, diarginine diprotoporphyrinate (PP(Arg)2) and N,N-diphenylalanyl protoporphyrin (PP(Phe)2), and the synergistic effect of 5-methoxyposralen (5-MOP) have been studied in comparison with that of protoporphyrin IX (PPIX). Under ultraviolet-A (UV-A) irradiation (lambda=365 nm), the phototoxicity of the porphyrins toward cultured human fibroblasts and keratinocytes decreases in the order: PPIX > PP(Arg)2 > PP(Phe)2. A synergistic effect of 5-MOP on the phototoxicity of PPIX, PP(Arg)2 and PP(Phe)2 has been observed. The combination of PPIX, PP(Arg)2 and PP(Phe)2 with 0.1-0.5 microM 5-MOP significantly potentiates the phototoxicity of the three porphyrins. The most effective potentiation was observed with the water-soluble PP(Arg)2 and 5-MOP concentrations lower than 0.75 microM. Above this 5-MOP concentration this potentiation is abolished. The intracellular concentration of PPIX and PP(Phe)2 is independent of the presence of 5-MOP. On the other hand, the intracellular content of PP(Arg)2 is decreased in a concentration-dependent manner by the psoralen. Illumination with red light, not absorbed by 5-MOP, leads to a weak potentiation of the PP(Arg)2 phototoxic effect in the presence of 5-MOP, suggesting that dark interaction of 5-MOP with cell membranes aggravated by porphyrin photosensitization is involved in the observed phenomena. The results are tentatively explained by differences in hydrophobicity and molecular structures of the examined photosensitizers. PPIX, which is barely soluble in water, has a significantly higher affinity for cell membranes and simultaneously exerts a stronger phototoxic effect than PP(Arg)2 whose solubility in water is high. On the other hand, the weak phototoxicity of PP(Phe)2 could be explained by the steric hindrance brought by the phenylalanyl substituents on the pyrrole ring. The loss in the PP(Arg)2 cell content probably explains the inhibition of the synergistic effect of 5-MOP on the PP(Arg)2 phototoxicity at high 5-MOP concentration. This study suggests that PP(Arg)2 in combination with 5-MOP might reveal a strong phototoxic effect when applied to skin cancer treatment.     

Conformational analysis of some ortho-hydroxyazoic dyes by the PCILO method

The quantum mechanical MO method PCILO is used to perform a detailed conformational analysis of ortho-hydroxyazobenzene and 1-phenyl azo 2-napthol. Several energy minima are obtained for each compound, after a simultaneous optimization of the main geometric parameters. Comparison is made with the corresponding para compounds. The calculated results are discussed in relation to the available experimental data.