Acid Group In Position Research Articles

First asymmetrically beta-tetrasubstituted porphyrin-based discotic lamellar liquid crystal

The synthesis and liquid crystalline properties of a new asymetrically tetrasubstituted porphyrin, namely 2,4-bis[2-(o-didodecyloxyphenoxycarbonyl)ethenyl]-6,7-bis[2-(m -didodecyloxycarbonyl)ethyl]-1,3,5,8-tetramethylporphyrin, 1 (figure 1), obtained from a commercially available porphyrin, hemin 2, are reported here. The synthetic route basically consists of two reactions: on the one hand, one esterification of the two propionic acid groups in positions 6 and 7 in the hemin 2 with the phenol 12, and on the other hand, a Heck-type reaction between the two vinyl groups in positions 2 and 4 of the hemin 2 and the iodo-aryl derivative 9. This is the first example of a porphyrin-based discotic liquid crystal which is neither symmetrically substituted nor prepared via total synthesis from monopyrrole units. It exhibits a well-defined enantiotropic discotic lamellar mesophase (DL) in a range of temperature from -2°C to the clearing point at 70°C. This interval includes room temperature, which makes this molecule suitable for a wide variety of applications.

1,3-Disubstituted-2-carboxy quinolones: highly potent and selective endothelin A receptor antagonists

The design, synthesis, and in vitro biological activity of a series of 2-carboxy quinolone antagonists selective for the endothelin A receptor are presented. Introduction of a second acid group in position 3 of the quinolone ring increases dramatically the selectivity for ET A.

Synthesis, biological evaluation, and structure-activity relationships of 3-acylindole-2-carboxylic acids as inhibitors of the cytosolic phospholipase A2.

3-Acylindole-2-carboxylic acid derivatives were prepared and evaluated for their ability to inhibit the cytosolic phospholipase A2 of intact bovine platelets. To define the structural requirements for enzyme inhibition, the carboxylic acid group, the acyl residue, and the moiety in position 1 were systematically modified. Furthermore, different substituents were introduced into the phenyl part of the indole. Replacement of the carboxylic acid group in position 2 of the indole with an acetic or propionic acid substituent led to a decrease of inhibitory potency. Enzyme inhibition was optimal when the acyl residue in position 3 had a length of 12 or more carbons. Conformational restriction of the acyl residue did not influence activity. Introduction of alkyl chains at position 1 of the indole with 8 or more carbons resulted in a loss of activity. However, replacing the omega-methyl group of such compounds with a carboxylic acid moiety was found to increase inhibitory potency significantly. Among the tested indole derivatives, 1-[2-(4-carboxyphenoxy)ethyl]-3-dodecanoylindole-2-carboxyli c acid (29b) had the highest potency. With an IC50 of 0.5 microM it was about 20-fold more active than the standard cPLA2 inhibitor arachidonyl trifluoromethyl ketone (IC50: 11 microM).

Heterocyclic azo dyestuffs in analytical chemistry. Part I. The ligand properties of 2-(2-pyridylazo)-1-naphthol and its sulphonated analogues

The preparation, from 2-hydrazinopyridine and the respective 1,2-naphthaquinones, of 2-(2-pyridylazo)-1-naphthol (α-PAN) and its derivatives containing sulphonic acid groups in positions 4 to 8 of the naphthalene ring, respectively, is described. The metal-complexing properties of the dyes are discussed in relationship to the position of the sulphonic acid group, and compared with those of 1-(2-pyridylazo)-2-naphthol (β-PAN). The dye with the sulphonic acid group in position 8 appears to be the most promising colorimetric reagent. All the new dyes are shown to be superior indicators to β-PAN for the complexometric titration of copper.

Heterocyclic azo dyestuffs in analytical chemistry. Part II. The ligand properties of 2-(2-pyrimidylazo)-1-naphthol and its sulphonated analogues

The preparation, from 2-hydrazinopyrimidine and the respective 1,2-naphthaquinones, of 2-(2-pyrimidylazo)-1-naphthol and its derivatives containing sulphonic acid groups in positions 4 to 8 of the naphthalene ring, respectively, is described. The metal-complexing properties of the dyes have been studied, and they are critically compared with their pyridyl analogues as analytical reagents. The dyes produce larger bathochromic shifts on chelation, and form complexes of lower stability. These two facts indicate that the dyes should be capable of higher selectivity than their pyridyl analogues. They are found to be better indicators for the titration of copper and better chromatographic spray reagents than their pyridyl analogues.