Comparative inhibitory activity of 3′- and 5′-functionalized nucleosides on ribonuclease A

Carboxymethyl tethered poly(disubstituted)triazoles built on nucleoside skeletons: A unique class of ribonuclease A inhibitors designed using chemical logic

Molecular docking of N-1,4-disubstituted-1,2,3-triazole tethered carboxymethylated thymidine and uridine with ribonuclease A, indicated their possible binding with the P₁, B₁ and P₂ subsites with varied efficiencies. This theoretical study in combination of our earlier experimental observations was used as the guiding principles for designing a range of 1,4-disubstituted 1, 2, 3- triazole tethered carboxymethylated pyrimidine nucleosides. Triazoles are biologically important molecules and at the same time easily accessible through less complicated synthetic routes as reported about two decades back in the context of "click" reactions. Regioselective propargylation of the nucleosides under controlled conditions followed by the use of CuAAC strategy afforded mono-, bis-, tris- and tetratriazolyl pyrimidine nucleosides. Although the characteristics of nucleosides were lost in these densely functionalized polyheterocycles, the catalytic efficiency of ribonuclease A was significantly reduced by these molecules which were investigated experimentally and by docking studies. Triazoles as linkers helped one or more acidic groups to reach the P₁ subsite of ribonuclease A. Enzyme kinetics showed that the efficiency of inhibition reached the highest point with an optimum number of functional groups and were not linearly dependent on the number of triazole tethered carboxymethyl groups. The location of the triazole ring in the molecule affected the efficiency and nature of inhibition which were the result of the overall structure of the modified nucleosides. Thus, the tris-triazolylated thymidine derivative (T-3', 5', N-tris-CH₂TzCH₂COOH) as opposed to tetra-triazolylated uridine (U-2', 3', 5', N-tetrakis-CH₂TzCH₂COOH) emerged as the best inhibitor with an inhibition constant value of 2.3 ± 0.05 µM.

Synthesis of Truncated Carbocyclic Nucleosides Using 5'-Deoxy-5'-Heteroarylsulfonylnucleosides

This article describes the detailed protocol for the synthesis of "truncated" carbocyclic nucleosides with a cyclopentene core and without a 4'-hydroxymethyl group. The synthesis was performed using 5'-deoxy-5'-heteroarylsulfonylnucleosides, which were prepared by the 5'-O-mesylation of the appropriately protected nucleosides, followed by a nucleophilic substitution with heteroarylthiols and the oxidation of the resulting 5'-S-heteroaryl-5'-thionucleosides. The treatment of the 5'-deoxy-5'-heteroarylsulfonylnucleosides with 1,8-diazabicyclo[5.4.0]undec-7-ene affords the truncated carbocyclic nucleosides, presumably via a domino reaction involving the α-deprotonation of the heteroarylsulfone, elimination of the nucleobase, formation of an α,β-unsaturated sulfone, Michael addition of the nucleobase to the α,β-unsaturated sulfone, and an intramolecular Julia-Kocienski reaction. This protocol would be useful for the short-step synthesis of biologically active carbocyclic nucleosides. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Preparation of 5'-deoxy-5'-heteroarylsulfonylnucleosides Basic Protocol 2: Synthesis of truncated carbocyclic nucleosides.

Organocatalytic Conversion of Nucleosides to Furanoid Glycals

A class of organocatalysts that are highly active for the conversion of 2'-deoxynucleosides to furanoid glycals have been discovered. These phosphorimides, (Ph₂PS)₂NH and (Ph₂PSe)₂NH, were shown to effectively mediate persilylation of 2'-deoxynucleosides allowing the elimination of the nucleobase giving the corresponding glycal. These mild conditions were demonstrated in the syntheses of glycals with various substitution patterns while minimizing the formation of undesired byproducts and expanding the scope of this methodology.

Carboxylated acyclonucleosides: synthesis and RNase A inhibition

Strategically designed carboxylated acyclonucleosides have been probed as a new class of RNase A inhibitors. Several experimental and theoretical studies have been performed to compile relevant qualitative and quantitative information regarding the nature and extent of inhibition. The inhibition constant (Ki) values were determined using a UV-based kinetics experiment. The changes in the secondary structure of the enzyme upon binding with the inhibitors were obtained from circular dichroism studies. The binding constants for enzyme-inhibitor interactions were determined with the help of fluorescence spectroscopy. Docking studies were performed to reveal the possible binding sites of the inhibitors within the enzyme. The cytosine analogues were found to possess better inhibitory properties in comparison to the corresponding uracil derivatives. An increment in the number of carboxylic acid groups (-COOH) in the inhibitor backbone was found to result in better inhibition.

A naphthalene-containing amino acid enables hydrogelation of a conjugate of nucleobase-saccharide-amino acids

Here we report the first example of a hydrogelator made of a conjugate of nucleobase-saccharide-amino acids by incorporating L-3-(2-naphthyl)-alanine to the conjugate, which illustrates a facile and effective method for generating bioactive and functional hydrogelators from the basic biological building blocks.