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PubMed1992

[Acid-base equilibrium of hydrazone derivatives 4-R-3R1-thazol-2-one. I. Ionization constants of alpha-methyl-beta-(4-R-thiazol-2-yl)- and alpha-methyl-beta-(4-R-3-R1-thiazol-2-ylidene)-hydrazides of benzoic acid].

The ionization constants of the following compounds have been determined spectrophotometrically in aqueous solution: [table: see text] The comparison of absorption spectra in UV and pK values of the compounds being described in this work and of the derivatives having a thiazole or thiazoline structure which were studied previously let us suggest that in the II-H neutral molecule and the I-H and II-H mono-anion the thiazole form prevails while in the case of the I-H neutral molecule the thiazoline form is more probable.

Acid-Base Equilibrium↗
PubMed1980

[Compounds with antitumor activity. V. Hydrazone derivatives of 5-formylimidazo(2,1-b)thiazoles and 6-substituted 2,3-dihydro-5-formylimidazo(2,1-b)thiazoles].

The synthesis of 2,3-dihydro-5-formylimidazo[2,1-b]thiazoles with different substituents at position 6 (CH3, C6H5, Cl, Br) is reported; thiosemicarbazones and tosylhydrazones were prepared from these aldehydes and from the 2,3-unsaturated analogues: these derivatives, submitted to a preliminary test, did not show significant antileukemic activity.

Animals↗
PubMed1977

Antiprotozoal thiazoles. 2. 2-(5-Nitro-2-furyl-, thiazolyl-, and 1-methylimidazolyl-)thiazoles.

Ten 2-substituted 4-thiazolecarboxaldehyde hydrazones bearing 5-nitro-2-furyl, 5-nitro-2-thiazolyl, and 1-methyl-5-nitro-2-imidazolyl functions have been prepared and screened for activity against Trypanosoma cruzi infections in mice. The results permitted the ranking of these substituents in decreasing order of activity: 1-methyl-5-nitro-2-imidazolyl greater than 5-nitro-2-furyl greater than 5-nitro-2-thiazolyl, the last being inactive. Some structural features of the side chain necessary for optimum activity are discussed. The most active compound, 4-[[[2-(1-methyl-5-nitro-2-imidazolyl)-4-thiazolyl]methylene]amino]thiomorpholine 1,1-dioxide, compared favorably with the standard Nifurtimox against three recent clinical isolates of T. cruzi, including one with a high myocardial tissue infiltration.

Animals↗
PubMed2006

Synthesis and antitumor activity of guanylhydrazones from 6-(2,4-dichloro-5-nitrophenyl)imidazo[2,1-b]thiazoles and 6-pyridylimidazo[2,1-b]thiazoles(1).

The design and synthesis of antitumor imidazothiazole guanylhydrazones are reported. The compounds were submitted to NCI for testing. All but one were more active than methyl-GAG. A few compounds were selected for further studies in search of a possible mechanism of action. The results from these studies and a final search with the NCI COMPARE algorithm suggest that the guanylhydrazones described in this paper are acting through a novel mechanism of action.

Adenosylmethionine Decarboxylase↗
PubMed1993

Induction of rat liver microsomal epoxide hydrolase by thiazole and pyrazine: hydrolysis of 2-cyanoethylene oxide.

Liver microsomal epoxide hydrolase (mEH) is active in the detoxification of epoxide-containing carcinogens. The effects of thiazole and pyrazine, constituents of tobacco and tobacco smoke as well as of a variety of foods, on the expression and regulation of mEH were examined in rats (200 mg/kg body wt/day, i.p., 1-3 days). Immunoblot analyses using rabbit anti-rat mEH antibody revealed a significant increase in mEH levels in hepatic microsomes isolated from either thiazole- or pyrazine-treated animals. Another protein (approximately 43 kd) cross-reacting with polyclonal mEH antibody was found to be increased concomitantly following pyrazine treatment. Northern and slot blot analyses showed substantial increases in mEH mRNA following either thiazole or pyrazine treatment. The level of mEH mRNA increased 17-fold at 24 h following thiazole treatment, relative to control. Approximately 20- and 16-fold increases in mEH mRNA were also observed at 48 and 72 h respectively following treatment with pyrazine. The level of polymerase chain reaction (PCR)-amplified mEH DNA derived from poly(A)+ RNA was clearly elevated following either thiazole or pyrazine treatment relative to that from untreated animals. Both sense and antisense strands of PCR-amplified mEH DNA were cloned into an M13mp19 phage vector in order to examine the nucleotide sequences of PCR-amplified mEH DNA derived from the poly(A)+ RNA isolated from thiazole- or pyrazine-treated animals. Sequence analyses revealed that the sequence of PCR-amplified DNA from the induced mRNA was identical to that published for mEH cDNA. Epoxide hydrolase activity toward the hydrolysis of 2-cyanoethylene oxide (CEO), the epoxide metabolite of the rat carcinogen acrylonitrile, was not significant in hepatic microsomes from untreated rats, but was substantially induced by treatment with thiazole or pyrazine. Microsomal hydrolysis activity was heat-sensitive and potently inhibited by 1,1,1-trichloropropene-2,3-oxide, indicating that mEH was the catalyst. The Vmax for the hydrolysis of CEO by hepatic microsomes from thiazole-treated rats (13.4 nmol/min/mg protein) was 1.5-fold greater than that with microsomes from pyrazine-treated rats, whereas similar Km values (approximately 1 mM) were observed for both microsomal preparations. These kinetic data correlate well with the increases in mEH mRNA observed after administration of thiazole or pyrazine to rats. These results provide evidence that administration of thiazole or pyrazine induces mEH with a large increase in mEH mRNA, and that the induced mEH catalyzes the hydrolysis of CEO.

Animals↗
PubMed2002

Fluorescent properties of oligonucleotide-conjugated thiazole orange probes.

The fluorescence properties of thiazole orange, linked via a (1) hydrophobic alkyl or a (2) hydrophilic ethylene glycol chain to the central internucleotidic phosphate group of a pentadeca-2'-deoxyriboadenylate (dA15), are evaluated. Linkage at the phosphate group yields two stereoisomers, S-isomer of the phosphorus chiral center (Sp) and R-isomer of the phosphorus chiral center (Rp); these are studied separately. The character of the linkage chain and the chirality of the internucleotidic phosphate linkage site influence the fluorescent properties of these thiazole orange-oligonucleotide conjugates (TO-probes). Quantum yields of fluorescence (phifl) of between 0.04 and 0.07 were determined for the single-stranded conjugates. The fluorescence yield increased by up to five times upon hybridization with the complementary sequence (d5'[CACT15CAC3']); (phifl values of between 0.06-0.35 were determined for the double-stranded conjugates. The phifl value (0.17) of thiazole orange, 1-(N,N'-trimethylaminopropyl)-4-[3-methyl-2,3-dihydro-(benzo-1,3-thiazole)-2-methylidene]-quinolinium iodide (TO-Pro 1) in the presence of the oligonucleotide duplex (TO-Pro 1: dA15.d5'[CACT15CAC3'] (1:1)) is much less than that for some of the hybrids of the conjugates. Our studies, using steady-state and time-resolved fluorescence experiments, show that a number of discrete fluorescent association species between the thiazole orange and the helix are formed. Time-resolved studies on the four double-stranded TO-probes revealed that the fluorescent oligonucleotide-thiazole orange complexes are common, only the distribution of the species varies with the character of the chain and the chirality at the internucleotidic phosphate site. Those TO-probes in which the isomeric structure of the phosphate-chain linkage is Rp, and therefore such that the fluorophore is directed toward the minor groove, have higher phifl values than the Sp isomer. Of the systems studied, thiazole orange linked by an alkyl chain to the internucleotidic phosphate (Rp isomer) has the highest phifl and the greatest fraction of the longest-lived fluorescent thiazole orange species (in the hybrid form).

Benzothiazoles↗
PubMed1988

Ara-tiazofurin: conservation of structural features in an unusual thiazole nucleoside.

Tiazofurin (2-beta-D-ribofuranosylthiazole-4-carboxamide, NSC 286193) is a C-glycosyl thiazole nucleoside with antitumor activity. Crystal structures of tiazofurin and its alpha,2'-deoxy and xylo analogues all show close contacts between the thiazole sulfur (S) and the furanose ring oxygen (O1'). These contacts have been interpreted in terms of an attractive intramolecular S-O interaction in the thiazole nucleosides. Ara-tiazofurin (2-beta-D-arabinofuranosylthiazole-4-carboxamide, ara-T) is the inactive arabinose analogue of tiazofurin. The crystal structure of ara-T is reported. This structure provides evidence for an attractive S-O interaction not seen in the other thiazole nucleosides. The conformation about the C-glycosyl bond in ara-T is such that close contacts are formed between the thiazole sulfur and both O1' and the 2'-hydroxyl oxygen O2'. This conformation is interpreted in terms of an additional attractive interaction between S and O2'. This interpretation is supported by comparison of the conformation of ara-T with those of other ara-nucleosides. These findings provide further evidence for an attractive S-O interaction in the thiazole nucleosides. Ara-T also demonstrates a second conformational feature found in these compounds: the carboxamide nitrogen remains cis to the thiazole nitrogen. Implications of these potentially constrained conformational features are discussed in terms of the mechanism of activity of tiazofurin.

Chemical Phenomena↗