EST64454: a Highly Soluble σ Receptor Antagonist Clinical Candidate for Pain Management.

The synthesis and pharmacological activity of a new series of pyrazoles that led to the identification of 1-(4-(2-((1-(3,4-difluorophenyl)-1-pyrazol-3-yl)methoxy)ethyl)piperazin-1-yl)ethanone (, EST64454) as a σ receptor (σR) antagonist clinical candidate for the treatment of pain are reported. The compound is easily obtained through a five-step synthesis suitable for the production scale and shows an outstanding aqueous solubility, which together with its high permeability in Caco-2 cells will allow its classification as a BCS class I compound. It also shows high metabolic stability in all species, linked to an adequate pharmacokinetic profile in rodents, and antinociceptive properties in the capsaicin and partial sciatic nerve ligation models in mice.

Pyrazolo[3,4-]pyrimidines as sigma-1 receptor ligands for the treatment of pain. Part 2: Introduction of cyclic substituents in position 4.

The replacement of acylamino by cyclic substituents in the position 4 of the pyrazolo[3,4-]pyrimidine scaffold, led to highly active sigma-1 receptor (σR) ligands. Phenyl or pyrazolyl groups were the best in terms of affinity for the σR and the 4-(1-methylpyrazol-5-yl) derivative, , was the most selective. Compound is also one of the best σR ligands ever described in terms of lipophilic ligand efficiency, which translates into a good physicochemical and ADMET profile.

Mechanistic investigation on the formation of indolizines from 2-enynylpyridines.

2,3,7-Trisubstituted indolizines were obtained from E- or Z-2-enynyl-4-substituted pyridines. The mechanistic pathway involves a base-catalyzed double-bond isomerization, if the E-isomer is the starting material, followed by a concerted pseudocoarctate cyclization.

Convergent stereoselective synthesis of the visual pigment A2E.

[chemical reaction: see text]. A stereoselective total synthesis of the visual pigment A2E has been achieved with use of palladium-catalyzed cross-coupling reactions in all key steps: a regioselective Suzuki or Negishi coupling of 2,4-dibromopyridine, a Sonogashira reaction, and a double Stille cross-coupling to complete the bispolyenyl skeleton.