"Dark" Singlet Oxygen and Electron Paramagnetic Resonance Spin Trapping as Convenient Tools to Assess Photolytic Drug Degradation.

Forced degradation studies are an important tool for a systematic assessment of decomposition pathways and identification of reactive sites in active pharmaceutical ingredients (APIs). Two methodologies have been combined in order to provide a deeper understanding of singlet oxygen-related degradation pathways of APIs under light irradiation. First, we report that a "dark" singlet oxygen test enables the investigation of drug reactivity toward singlet oxygen independently of photolytic irradiation processes. Second, the photosensitizing properties of the API producing the singlet oxygen was proven and quantified by spin trapping and electron paramagnetic resonance analysis. A combination of these techniques is an interesting addition to the forced degradation portfolio as it can be used for (1) revealing unexpected degradation pathways of APIs due to singlet oxygen, (2) clarifying photolytic drug-drug interactions in fixed-dose combinations, and (3) synthesizing larger quantities of hardly accessible oxidative drug degradants.

Organocatalytic Asymmetric Synthesis of Functionalized 1,3,5-Triarylpyrrolidin-2-ones via an Aza-Michael/Aldol Domino Reaction.

The organocatalytic asymmetric synthesis of functionalized 1,3,5-triarylpyrrolidin-2-ones bearing three contiguous stereocenters through an aza-Michael/aldol domino reaction of α-ketoamides with α,ß-unsaturated aldehydes is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions. The reaction proceeds with excellent diastereoselectivities (>20:1) and good to excellent enantioselectivities (60-96% ee).

An Asymmetric Organocatalytic Quadruple Cascade to Tetraaryl-Substituted 2-Azabicyclo[3.3.0]octadienones.

A new asymmetric organocatalytic three-component quadruple cascade of α-ketoamides with α,ß-unsaturated aldehydes is described. The reaction is catalyzed by the (S)-diphenylprolinol TMS ether catalyst and proceeds via an aza-Michael/aldol condensation/vinylogous Michael/aldol condensation sequence to yield tetraaryl-substituted 2-azabicyclo[3.3.0]octadienone derivatives. The cascade products are obtained with good to very good yields (34-71%), virtually complete diastereoselectivities (>20:1), and very good enantioselectivities (84-97%).

Chemistry, antiproliferative activity and low nephrotoxicity of 3,5-diacetyl-1,2,4-triazol bis(4N-thiosemicarbazone) ligands and their platinum(II) complexes.

The preparation and characterization of 3,5-diacetyl-1,2,4-triazol bis(4,4-dimethylthiosemicarbazone) ligand, H(3)L(1), and its dinuclear platinum complex [Pt(mu-HL(1))](2) is described. The crystal and molecular structure of the platinum complex has been resolved by single crystal X-ray diffraction. The ligands coordinate, in an asymmetric dideprotonate form, to the platinum ions in a tridentate fashion (NNS) and S-bridging bonding modes. Thus the molecular units of the platinum complexes are stacked as dimers. The new compounds synthesized together with the analogous monosubstituted ligand 3,5-diacetyl-1,2,4-triazol bis(4-methylthiosemicarbazone) (H(5)L(2)) and its dinuclear platinum(ii) complex [Pt(mu-H(3)L(2))](2) have been evaluated for antiproliferative activity in vitro against NCI-H460, A2780 and A2780cisR human cancer cell lines. The cytotoxicity data suggest that these compounds may be endowed with important antitumor properties, especially H(3)L(1) and [Pt(mu-H(3)L(2))](2) since they not only circumvent cisplatin resistance in A2780cisR cells but also exhibit high antiproliferative activity in human non-small cell lung cancer NCI-H460 cells. Subsequent nephrotoxic study, in LLC-PK1 cells, show that the four compounds investigated exhibit very low nephrotoxicity with respect to cisplatin.