Unexpected O–H Insertion of Rhodium-Azavinylcarbenes with <i>N</i>‑Acylhydrazones: Divergent Synthesis of 3,6-Disubstituted- and 3,5,6-Trisubstituted-1,2,4-Triazines

A practical and efficient method for divergent synthesis of 3,6-disubstituted- and 3,5,6-trisubstituted-1,2,4-triazines via unexpected rhodium-catalyzed O–H insertion/rearrangement/conditions-controlled intramolecular cyclization and oxidation reaction under mild conditions has been developed. Notably, it is the first example for the synthesis of 1,2,4-triazines with different substituted-patterns via a common intermediate with excellent chemoselectivities by the reaction of <i>N</i>-acylhydrazones as aze-[3C] or [4C] synthons with <i>N</i>-sulfonyl-1,2,3-triazoles as aze-[2C] synthons. Furthermore, this method allows direct access to di­(het)­aryl ketone frameworks containing 1,2,4-triazine moiety for the first time, serving as a versatile building block for the synthesis of other useful heterocyclic skeletons, such as pyridine or pyridazinone-fused triazine in excellent yields

Unexpected O–H Insertion of Rhodium-Azavinylcarbenes with <i>N</i>‑Acylhydrazones: Divergent Synthesis of 3,6-Disubstituted- and 3,5,6-Trisubstituted-1,2,4-Triazines

A practical and efficient method for divergent synthesis of 3,6-disubstituted- and 3,5,6-trisubstituted-1,2,4-triazines via unexpected rhodium-catalyzed O–H insertion/rearrangement/conditions-controlled intramolecular cyclization and oxidation reaction under mild conditions has been developed. Notably, it is the first example for the synthesis of 1,2,4-triazines with different substituted-patterns via a common intermediate with excellent chemoselectivities by the reaction of <i>N</i>-acylhydrazones as aze-[3C] or [4C] synthons with <i>N</i>-sulfonyl-1,2,3-triazoles as aze-[2C] synthons. Furthermore, this method allows direct access to di­(het)­aryl ketone frameworks containing 1,2,4-triazine moiety for the first time, serving as a versatile building block for the synthesis of other useful heterocyclic skeletons, such as pyridine or pyridazinone-fused triazine in excellent yields

Immunohistochemical staining of CA XV and CA II in parallel sections of mouse kidney.

<p>In the cortex, the expression of CA XV (A) is more limited compared to CA II (B) that is mainly expressed in the collecting ducts (arrows) and proximal tubules (asterisks). Arrowheads show the thick ascending limbs of Henle, which are positively stained for CA XV. In the medulla, only a very faint reaction is seen for CA XV (C) in the collecting ducts (arrows), while the staining for CA II (D) is more intense. Original magnifications x400.</p

Immunohistochemical staining of CA XV in the mouse kidney.

<p>A sectional view of mouse kidney shows that CA XV is expressed in the cortex, and a weaker reaction is seen in the collecting ducts of the outer medulla (A). Intense staining is seen in the thick ascending limbs (B) and collecting ducts of the cortex (C). Original magnifications x100 (A), x630 (B,C).</p

Quantitative real-time PCR analysis of <i>Car15</i> mRNA levels in the kidney specimens of wild type and <i>Car4^−/−</i> and <i>Car14^−/−</i> knockout mice.

<p>Three of five kidney samples from <i>Car14^−/−</i> knockout (KO) mice showed slightly increased expression of <i>Car15</i> mRNA in comparison to the wild type (WT) and <i>Car4^−/−</i> kidneys, but the difference between the groups showed no statistical significance.</p

Confirmation of CA XV immunostaining in the thick ascending limb of Henle.

<p>Tamm-Horsfall glycoprotein (THP) antibody was used as a marker (B). CA XV (A) clearly labels the thick ascending limbs (arrows) and collecting ducts (arrowheads). Original magnifications x400.</p

Western blot of recombinant mouse CA XV identified with the new anti-CA XV antibody.

<p>The antibody identifies a 34- to 36-kDa polypeptide and a smaller 31-kDa polypeptide that is suggested to be a non-glycosylated form of CA XV (left). Pre-immune serum showed no reaction (right).</p

Cloning, Characterization, and Sulfonamide and Thiol Inhibition Studies of an α‑Carbonic Anhydrase from <i>Trypanosoma cruzi</i>, the Causative Agent of Chagas Disease

An α-carbonic anhydrase (CA, EC 4.2.1.1) has been identified, cloned, and characterized from the unicellular protozoan <i>Trypanosoma cruzi</i>, the causative agent of Chagas disease. The enzyme (TcCA) has a very high catalytic activity for the CO₂ hydration reaction, being similar kinetically to the human (h) isoform hCA II, although it is devoid of the His64 proton shuttle. A large number of aromatic/heterocyclic sulfonamides and some 5-mercapto-1,3,4-thiadiazoles were investigated as TcCA inhibitors. The aromatic sulfonamides were weak inhibitors (<i>K</i>_I values of 192 nM to 84 μM), whereas some heterocyclic compounds inhibited the enzyme with <i>K</i>_I values in the range 61.6–93.6 nM. The thiols were the most potent in vitro inhibitors (<i>K</i>_I values of 21.1–79.0 nM), and some of them also inhibited the epimastigotes growth of two <i>T. cruzi</i> strains in vivo

Protein–Protein Interactions: Inhibition of Mammalian Carbonic Anhydrases I–XV by the Murine Inhibitor of Carbonic Anhydrase and Other Members of the Transferrin Family

The murine inhibitor of carbonic anhydrase (mICA), a member of the transferrin (TF) superfamily of proteins, together with human holo- and apoTF and lactoferrin (LF) were assessed as inhibitors of all catalytically active mammalian (h = human, m = murine) CA isoforms, from CA I to CA XV. mICA was a low nanomolar to subnanomolar inhibitor of hCAs I, II, III, VA, VB, VII and mCAs XV (<i>K</i>_I of 0.7–44.0 nM) and inhibited the remaining isoforms with <i>K</i>_I of 185.5–469 nM. hTF, apoTF, and hLF were inhibitors of most of these CAs but with reduced efficiency compared to mICA (<i>K</i>_I of 18.9–453.8 nM). Biacore surface plasmon resonance and differential scanning calorimetry experiments were also used for obtaining more insights into the interaction between these proteins, which may be useful for drug design of protein-based CA inhibitors

Cloning, Characterization, and Inhibition Studies of a β‑Carbonic Anhydrase from Leishmania donovani chagasi, the Protozoan Parasite Responsible for Leishmaniasis

Leishmaniasis is an infection provoked by protozoans belonging to the genus Leishmania. Among the many species and subsepecies of such protozoa, Leishmania donovani chagasi causes visceral leishmaniasis. A β-carbonic anhydrase (CA, EC 4.2.1.1) was cloned and characterized from this organism, denominated here LdcCA. LdcCA possesses effective catalytic activity for the CO₂ hydration reaction, with <i>k</i>_cat of 9.35 × 10⁵ s^–1 and <i>k</i>_cat/K_M of 5.9 × 10⁷ M^–1 s^–1. A large number of aromatic/heterocyclic sulfonamides and 5-mercapto-1,3,4-thiadiazoles were investigated as LdcCA inhibitors. The sulfonamides were medium potency to weak inhibitors (<i>K</i>_I values of 50.2 nM–9.25 μM), whereas some heterocyclic thiols inhibited the enzyme with <i>K</i>_Is in the range of 13.4–152 nM. Some of the investigated thiols efficiently inhibited the in vivo growth of Leishmania chagasi and Leishmania amazonensis promastigotes, by impairing the flagellar pocket and movement of the parasites and causing their death. The β-CA from Leishmania spp. is proposed here as a new antileishmanial drug target