Metal-Free Aerobic Oxidation of Nitro-Substituted Alkylarenes to Carboxylic Acids or Benzyl Alcohols Promoted by NaOH

Thermodynamic Insights on the Structure-Property Relationships in Substituted Benzenes: Are the Pairwise Interactions in Tri-Substituted Methyl-Nitro-Benzoic Acids Still Valid?

A comprehensive experimental thermochemical study of nine methyl-substituted nitrobenzoic acids was carried out, leading to the final standard molar enthalpies of formation in the gas phase. The combustion energies were measured using high-precision combustion calorimetry, and the enthalpies of formation of the crystal phase were derived. The sublimation enthalpies were obtained from the vapor pressure-temperature dependencies measured using the classic Knudsen effusion mass loss and the transpiration methods. The standard molar enthalpies of vaporisation were derived from the temperature dependence of the mass-loss rates measured using the non-isothermal thermogravimetry. The thermal behaviour, including melting temperatures and standard molar enthalpies of fusion, was investigated by DSC. The high-level quantum chemical G* methods were used for the mutual validation of the experimental and theoretical gas phase enthalpies of formation of methyl-substituted nitrobenzoic acids. The consistent set of experimental properties at the reference temperature T=298 K was evaluated and recommended for thermochemical calculations. The pairwise interactions of the substituents on the benzene ring were derived from nitro-toluenes, methyl-benzoic acids and nitro-benzoic acids available in the literature, and the additivity of the contributions when three substituents are placed simultaneously in the benzene ring was discussed.

O-Alkylazoxymycins A-F, Naturally Occurring Azoxy-Aromatic Compounds from Streptomyces sp. Py50

Six new azoxy-aromatic compounds (o-alkylazoxymycins A-F, 1-6) and two new nitrogen-bearing phenylvaleric/phenylheptanoic acid derivatives (o-alkylphemycins A and B, 7 and 8) were isolated from Streptomyces sp. Py50. Their structures were elucidated based on HRESIMS, NMR, UV spectroscopic analyses, and X-ray crystallographic data. O-Alkylazoxymycins A-F (1-6) are the first natural examples of azoxy compounds with the azoxy bond attached to the ortho-position of the phenylheptanoic acid or phenylvaleric acid moiety. Compounds 1, 5, and 6 were active against Epidermophyton floccosum with MIC₅₀ values ranging from 10.1 to 51.2 μM. A plausible biosynthetic pathway of 2 and 3 was proposed.

A Bioreductive Protecting Group for RNA Synthesis

This protocol describes a method for the preparation of ribonucleoside phosphoramidite bearing a bioreductive protecting group on the 2'-OH group and its application in the synthesis of bioreduction-responsive oligonucleotides. The protecting group used in this method consists of the modified 4-nitrobenzyl skeleton, which has gem-dimethyl groups at benzylic positions to enable deprotection under physiological conditions. Applying the synthesized ribonucleoside phosphoramidite to solid-phase synthesis of oligonucleotides, a 2'-O-protected oligonucleotide was obtained without any undesirable cleavages under standard oligonucleotide synthesis conditions. The 2'-O-protected oligonucleotide was then treated with a combination of nitroreductase (Escherichia coli) and NADH as a bioreduction system for cleavage of the 2'-O-protecting group. After reduction of the nitro group, the protecting group was deprotected in a time-dependent manner. Thus, this protection technology is a potential new tool for production of reduction-responsive RNA-based materials that can be used in life and medical sciences. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Synthesis of ribonucleoside phosphoramidite bearing a bioreductive protecting group Basic Protocol 2: Synthesis of 2'-O-protected oligonucleotides and their deprotection properties under bioreduction.

Development of Bioreduction Labile Protecting Groups for the 2'-Hydroxyl Group of RNA

Protection and deprotection of the 2'-hydroxyl group of RNAs are critical for RNA-based drug discovery. This paper reports development of a bioreduction labile protecting group of the 2'-hydroxyl group in RNA. After the reduction of the nitro group in a chemical or enzymatic manner, the protecting groups were removed spontaneously. The attachment of electron-donating groups to the benzene ring or benzylic carbon enabled fast and controllable deprotection of the 2'-hydroxyl protecting group under physiological conditions.