Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong h...

Many natural products contain unusual aromatic β-amino acids or moieties derived therefrom. The biosynthesis of these β-amino acids was first elucidated during a biosynthetic study of the enediyne antitumor antibiotic C-1027, when an enzyme, SgcC4, was discovered to convert L-tyrosine to (S)-β-tyrosine. SgcC4 is similar in sequence and structure to 4-methylideneimidazole-5-one (MIO)-containing ...

The ability of the isolated Ringer-perfused frog liver, to concentrate dyestuffs in its secretion several hundred times, can be abolished entirely and reversibly by replacing in the Ringer solution about 1/8 of the NaCl by the isosmotic amount of a surface-inactive non-electrolyte (disaccharide, hexose, pentose, polyhydric alcohol, amino acid, acid amide) or electrolyte (salts of lower fatty ac...

The acid-catalyzed decarboxylation reactions of indoleand pyrrole-carboxylic acids require the addition of one equivalent of water to the carboxyl group and a proton to the heterocyclic ring carbon at the position α to the carboxyl. Where α-protonation is thermodynamically favoured over β-protonation, the magnitude of the observed 12C/13C kinetic isotope effect (CKIE) is greater than where the ...

The skeletons of both independent mol-ecules of the carboxylic acid hemihydrate, C(10)H(8)N(2)O(10)·0.5H(2)O, are approximately planar [maximum deviations 0.642 (3) and 0.468 (1) Å]. The deviations arise from the twisting of the nitro groups with respect to the aromatic rings [dihedral angles = 3.24 (2) and 27.01 (1), and 7.87 (1) and 16.37 (2)° in the two molecules]. The crystal structure feat...

An alternative method for the synthesis of acetamidobenzimidazoles (3-6) has been developed, including reacylation methylbenzimidazol-2-ylcarbamate (carbendazim, MBC, 1) under action aliphatic and aromatic carboxylic acids. It was shown that with an increase in size alkyl group reaction temperature (in case butyric acid), due to decomposition resulting product, yield target acyl products sharpl...

Herein we present a highly efficient, light-mediated, deoxygenative protocol to access γ-oxo-α-amino acid derivatives. This radical methodology employs photoredox catalysis, in combination with triphenylphosphine, generate acyl radicals from readily available (hetero)aromatic and vinylic carboxylic acids. approach allows for the straightforward synthesis of acids bearing wide range functional g...

Introduction It has been proposed that oxygen functional groups (i.e., carboxylic acids and their salts, phenols, and ethers), prevalent in low rank coals, are responsible for cross-linking reactions that inhibit the efficient conversion of low-rank coals to liquid fuels and chemicals. In the pyrolysis and liquefaction of low-rank coals, cross-linking has been correlated with evolution of CO2 a...