Novel paramagnetic AT1 receptor antagonists

Characterization of crystalline and amorphous forms of irbesartan by multi-nuclear solid-state NMR

Irbesartan (IRB) is an antihypertensive drug which exhibits the rare phenomenon of desmotropy; its 1H- and 2H- tetrazole tautomers can be isolated as distinct crystalline forms. The crystalline forms of IRB are poorly soluble, hence the amorphous form is potentially of interest for its faster dissolution rate. The tautomeric form and the nature of hydrogen bonding in amorphous IRB are unknown. In this study, crystalline form A and amorphous form of irbesartan were studied using ¹³C, ¹⁵N and ¹H solid-state NMR. Variable-temperature ¹³C SSMNR studies showed alkyl chain disorder in the crystalline form of IRB, which may explain the conflicting literature crystal structures of form A (the marketed form). ¹⁵N NMR indicates that the amorphous material contains an approximately 2:1 ratio of 1H- and 2H-tetrazole tautomers. Static ¹H SSNMR and relaxation time measurements confirmed different molecular mobilities of the samples and provided molecular-level insight into the nature of the glass transition. SSNMR is shown to be a powerful technique to investigate the solid state of disordered active pharmaceutical ingredients.

Controlling biofilms on cultural materials: the role of 3-(dodecane-1-thiyl)-4-(hydroxymethyl)-2,2,5,5-tetramethyl-1-pyrrolinoxyl

3-(Dodecanethiyl)-4-(hydroxymethyl)-2,2,5,5-tetramethyl-1-pyrrolinoxyl (5) effectively disperses biofilms of relevance to cultural materials while preventing their formation.

Synthesis and biological evaluation of 4′-[(benzimidazol-1-yl) methyl]biphenyl-2-amides as dual angiotensin II and endothelin A receptor antagonists

Discovery of new benzimidazoles as potent dual AT₁ and ET_A receptor antagonists with the novel N-(1H-tetrazol-5-yl)-amide fragment.

Synthesis, physicochemical properties and antimicrobial activity of mono-/dinitroxyl amides

Two comparative sets of mono-/dinitroxyl amides were designed and prepared. The novel TEMPO and/or PROXYL derivatives were fully characterised and their spin, redox and antimicrobial properties were determined. Cyclic voltammetry revealed (quasi)reversible redox behavior for most of the studied radicals. Moreover, the electron-withdrawing substituents increased the oxidation potential of nitroxides in comparison to electron-donating groups. While EPR spectra of monoradicals featured the typical three-line signal, the spectra of biradicals showed more complex splitting patterns. The in vitro biological assay revealed that unlike pyrrolidinyl derivatives, the piperidinyl nitroxides significantly inhibited the growth of Staphylococcus sp.

Synthesis and biological evaluation of 4'-[(benzimidazole-1-yl)methyl]biphenyl-2-sulfonamide derivatives as dual angiotensin II/endothelin A receptor antagonists

A series of 4'-[(benzimidazole-1-yl)methyl]biphenyl-2-sulfonamide derivatives (Ia-Il) were synthesized and biologically evaluated. It was found that Ig, the most active compound, antagonized both Ang II AT(1) and endothelin ET(A) receptors (AT(1) IC(50)=8.5, ET(A) IC(50)=8.9 nM), and was more potent than losartan in RHRs with no significant effect on heart rate. The preliminary structure-activity relationships were also discussed in the present paper.