Ramón Badorrey

Organocatalyzed enantioselective desymmetrization of diols in the preparation of chiral building blocks.

Desymmetrization of diols is a powerful tool to the synthesis of chiral building blocks. Among the different approaches to perform discrimination between both enantiotopic hydroxyl groups, the organocatalytic approach has gained importance in the last years. A diverse range of organocatalysts has been used to efficiently promote this enantioselective transformation and this Minireview examines the different contributions in this field.

A novel pan-negative-gating modulator of KCa2/3 channels, fluoro-di-benzoate, RA-2, inhibits endothelium-derived hyperpolarization-type relaxation in coronary artery and produces bradycardia in vivo

Small/intermediate conductance KCa channels (KCa2/3) are Ca2+/calmodulin regulated K+ channels that produce membrane hyperpolarization and shape neurologic, epithelial, cardiovascular, and immunologic functions. Moreover, they emerged as therapeutic targets to treat cardiovascular disease, chronic inflammation, and some cancers. Here, we aimed to generate a new pharmacophore for negative-gating modulation of KCa2/3 channels. We synthesized a series of mono- and dibenzoates and identified three dibenzoates [1,3-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate) (RA-2), 1,2-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate), and 1,4-phenylenebis(methylene) bis(3-fluoro-4-hydroxybenzoate)] with inhibitory efficacy as determined by patch clamp. Among them, RA-2 was the most drug-like and inhibited human KCa3.1 with an IC50 of 17 nM and all three human KCa2 subtypes with similar potencies. RA-2 at 100 nM right-shifted the KCa3.1 concentration-response curve for Ca2+ activation. The positive-gating modulator naphtho[1,2-d]thiazol-2-ylamine (SKA-31) reversed channel inhibition at nanomolar RA-2 concentrations. RA-2 had no considerable blocking effects on distantly related large-conductance KCa1.1, Kv1.2/1.3, Kv7.4, hERG, or inwardly rectifying K+ channels. In isometric myography on porcine coronary arteries, RA-2 inhibited bradykinin-induced endothelium-derived hyperpolarization (EDH)–type relaxation in U46619-precontracted rings. Blood pressure telemetry in mice showed that intraperitoneal application of RA-2 (≤100 mg/kg) did not increase blood pressure or cause gross behavioral deficits. However, RA-2 decreased heart rate by ≈145 beats per minute, which was not seen in KCa3.1−/− mice. In conclusion, we identified the KCa2/3–negative-gating modulator, RA-2, as a new pharmacophore with nanomolar potency. RA-2 may be of use to generate structurally new types of negative-gating modulators that could help to define the physiologic and pathomechanistic roles of KCa2/3 in the vasculature, central nervous system, and during inflammation in vivo.

Chiral iminoesters derived from d-glyceraldehyde in [3+2] cycloaddition reactions. Asymmetric synthesis of a key intermediate in the synthesis of neuramidinase inhibitors

Silver-catalyzed endo-selective and copper-catalyzed exo-selective asymmetric [3 + 2] cycloadditions of acrylates to chiral iminoesters derived from D-glyceraldehyde have been investigated. The reaction diastereoselectively provides highly functionalized pyrrolidines. This approach was used to develop the first asymmetric synthesis of a key intermediate in the synthesis of pyrrolidine influenza neuramidinase inhibitors.

Asymmetric Homologation of Ketones. A New Entry to Orthogonally Protected (2R,4R)-Piperidine-2,4-dicarboxylic Acid

A new conformationally constrained analogue of glutamic acid has been synthesized efficiently in seven steps from a chiral 2-alkyl-4-piperidone. The synthesis is based on (a) the unprecedented asymmetric one-carbon homologation of the ketone controlled by the size of the N-substituent and (b) the appropriate manipulation of substituents at positions 2 and 4 of the piperidine ring, a step that involves two independent oxidation processes.

Vascular reactivity profile of novel KCa3.1‐selective positive‐gating modulators in the coronary vascular bed

Opening of intermediate‐conductance calcium‐activated potassium channels (KCa3.1) produces membrane hyperpolarization in the vascular endothelium. Here, we studied the ability of two new KCa3.1‐selective positive‐gating modulators, SKA‐111 and SKA‐121, to (1) evoke porcine endothelial cell KCa3.1 membrane hyperpolarization, (2) induce endothelium‐dependent and, particularly, endothelium‐derived hyperpolarization (EDH)‐type relaxation in porcine coronary arteries (PCA) and (3) influence coronary artery tone in isolated rat hearts. In whole‐cell patch‐clamp experiments on endothelial cells of PCA (PCAEC), KCa currents evoked by bradykinin (BK) were potentiated ≈7‐fold by either SKA‐111 or SKA‐121 (both at 1 μM) and were blocked by a KCa3.1 blocker, TRAM‐34. In membrane potential measurements, SKA‐111 and SKA‐121 augmented bradykinin‐induced hyperpolarization. Isometric tension measurements in large‐ and small‐calibre PCA showed that SKA‐111 and SKA‐121 potentiated endothelium‐dependent relaxation with intact NO synthesis and EDH‐type relaxation to BK by ≈2‐fold. Potentiation of the BK response was prevented by KCa3.1 inhibition. In Langendorff‐perfused rat hearts, SKA‐111 potentiated coronary vasodilation elicited by BK. In conclusion, our data show that positive‐gating modulation of KCa3.1 channels improves BK‐induced membrane hyperpolarization and endothelium‐dependent relaxation in small and large PCA as well as in the coronary circulation of rats. Positive‐gating modulators of KCa3.1 could be therapeutically useful to improve coronary blood flow and counteract impaired coronary endothelial dysfunction in cardiovascular disease.

Diastereoselective Construction of the 6-Oxa-2-azabicyclo[3.2.1]octane Scaffold from Chiral α-Hydroxyaldehyde Derivatives by Aza-Prins Reaction

(R)-2,3-Di-O-benzylglyceraldehyde and N-tosyl homoallylamine undergo aza-Prins cyclization to afford (1R,5S,7S)-7-[(benzyloxy)methyl]-2-tosyl-6-oxa-2-azabicyclo[3.2.1]octane in a highly diastereoselective manner through an unexpected intramolecular nucleophilic attack. Our work has opened a new route toward the asymmetric synthesis of 7-(alkyl or aryl)-6-oxa-2-azabicyclo[3.2.1]octane derivatives from chiral α-hydroxyaldehyde derivatives in one step.