Synthesis, structure and toxicity evaluation of ethanolamine nitro/chloronitrobenzoates: a combined experimental and theoretical study

BACKGROUND

Nitroaromatic and chloronitroaromatic compounds have been a subject of great interest in industry and recently in medical-pharmaceutic field. 2-Chloro-4-nitro/2-chloro-5-nitrobenzoic acids and 4-nitrobenzoic acid are promising new agents for the treatment of main infectious killing diseases in the world: immunodeficiency diseases and tuberculosis.

RESULTS

New ethanolamine nitro/chloronitrobenzoates were synthesized and characterized by X-ray crystallography, UV-vis, FT-IR and elementary analysis techniques. The toxicity of the compounds prepared and correspondent components was evaluated using Hydractinia echinata as test system. A significant lower toxicity was observed for nitro-derivative compared with chloronitro-derivatives and individual components. Crystallographic studies, together with the chemical reactivity and stability profiles resulted from density functional theory and ab initio molecular orbital calculations, explain the particular behavior of ethanolamine 4-nitrobenzoate in biological test.

CONCLUSIONS

The experimental and theoretical data reveal the potential of these compounds to contribute to the design of new active pharmaceutical ingredients with lower toxicity.

Experimental cocrystal screening and solution based scale-up cocrystallization methods

Cocrystals are crystalline single phase materials composed of two or more different molecular and/or ionic compounds generally in a stoichiometric ratio which are neither solvates nor simple salts. If one of the components is an active pharmaceutical ingredient (API), the term pharmaceutical cocrystal is often used. There is a growing interest among drug development scientists in exploring cocrystals, as means to address physicochemical, biopharmaceutical and mechanical properties and expand solid form diversity of the API. Conventionally, coformers are selected based on crystal engineering principles, and the equimolar mixtures of API and coformers are subjected to solution-based crystallization that are commonly employed in polymorph and salt screening. However, the availability of new knowledge on cocrystal phase behaviour in solid state and solutions has spurred the development and implementation of more rational experimental cocrystal screening as well as scale-up methods. This review aims to provide overview of commonly employed solid form screening techniques in drug development with an emphasis on cocrystal screening methodologies. The latest developments in understanding and the use of cocrystal phase diagrams in both screening and solution based scale-up methods are also presented. Final section is devoted to reviewing the state of the art research covering solution based scale-up cocrystallization process for different cocrystals besides more recent continuous crystallization methods.

An exploration into the amide–pseudo amide hydrogen bonding synthon between a new coformer with two primary amide groups and theophylline

Double the FUN! A rare amide–pseudo amide hydrogen bonding synthon has been established for the co-crystal between a new coformer with two primary amide groups and theophylline.

Ionic co-crystals of enantiopure and racemic histidine with calcium halides

Ionic co-crystals (ICCs) of l- and dl-histidine with CaCl₂, CaBr₂ and CaI₂ were prepared by mechanochemical and solution methods and were structurally characterized by either single crystal or powder X-ray diffraction methods.

Two modes of peri-interaction between an aldehyde group and a carboxylate anion in naphthalaldehydate salts

The naphthalaldehydate anion shows two modes of interaction between its functional groups: either a carboxylate oxygen atom makes an n–π* interaction with the aldehyde carbon atom, or the aldehyde hydrogen atom is directed to the face of the carboxylate group.

On the predictability of supramolecular interactions in molecular cocrystals – the view from the bench

A series of cocrystals involving theophylline and fluorobenzoic acids highlights the difficulty of predicting supramolecular interactions in molecular crystals.

Co-crystals and molecular salts of carboxylic acid/pyridine complexes: can calculated pKa's predict proton transfer? A case study of nine complexes

Prediction of proton transfer made only using the structural formula can predict at which range of calculated ΔpK_a's a co-crystal or a molecular salt forms in a series of carboxylic acid/pyridine complexes.

Crystalline adducts of the Lawsone molecule (2-hydroxy-1,4-naphthaquinone): optical properties and computational modelling

Crystal-engineering techniques allow the colour of the molecule in henna dye (Lawsone) to be tuned from yellow to red.

Binary co-crystals of the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene and camphoric acid

Co-crystals comprising the active pharmaceutical ingredient 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, C12H10N4, and the chiral co-formers (+)-, (-)- and (rac)-camphoric acid (cam), C10H16O4, have been synthesized. Two different stoichiometries of the API and co-former are obtained, namely 1:1 and 3:2. Crystallization experiments suggest that the 3:2 co-crystal is kinetically favoured over the 1:1 co-crystal. Single-crystal X-ray diffraction analysis of the co-crystals reveals N-H...O hydrogen bonding as the primary driving force for crystallization of the supramolecular structures. The 1:1 co-crystal contains undulating hydrogen-bonded ribbons, in which the chiral cam molecules impart a helical twist. The 3:2 co-crystal contains discrete Z-shaped motifs comprising three molecules of the API and two molecules of cam. The 3:2 co-crystals with (+)-cam, (-)-cam (space group P21) and (rac)-cam (space group P21/n) are isostructural. The enantiomeric co-crystals contain pseudo-symmetry consistent with space group P21/n, and the co-crystal with (rac)-cam represents a solid solution between the co-crystals containing (+)-cam and (-)-cam.

Hydrogen-bond coordination in organic crystal structures: statistics, predictions and applications

Statistical models to predict the number of hydrogen bonds that might be formed by any donor or acceptor atom in a crystal structure have been derived using organic structures in the Cambridge Structural Database. This hydrogen-bond coordination behaviour has been uniquely defined for more than 70 unique atom types, and has led to the development of a methodology to construct hypothetical hydrogen-bond arrangements. Comparing the constructed hydrogen-bond arrangements with known crystal structures shows promise in the assessment of structural stability, and some initial examples of industrially relevant polymorphs, co-crystals and hydrates are described.

Drug solid solutions – a method for tuning phase transformations

Tuning phase transformation temperatures through the use of solid solutions.

The role of a liquid in “dry” co-grinding: a case study of the effect of water on mechanochemical synthesis in a “l-serine–oxalic acid” system

[l-serH]₂[ox]·2H₂O form II proved to be an intermediate product in the reaction for obtaining the form I.

Crystal engineering of homochiral molecular organization of naproxen in cocrystals and their thermal phase transformation studies

Crystal engineering principles were used to produce the homochiral R- and S-chains of naproxen (NPX) by cocrystallization with bipyridine (BPY) and piperazine (PIZ).

Structural and physicochemical aspects of hydrochlorothiazide co-crystals

The drug–drug co-crystal of hydrochlorothiazide with pyrazinamide is a potential candidate for development of hydrochlorothiazide formulations for combinational therapy.

Pharmaceutical cocrystals and poorly soluble drugs

In recent years cocrystal formation has emerged as a viable strategy towards improving the solubility and bioavailability of poorly soluble drugs. In this review the success of numerous pharmaceutical cocrystals for the improvement of the solubility and dissolution rates of poorly soluble drugs is demonstrated using various examples taken from the literature. The role of crystal engineering principles in the selection of appropriate coformers and the nature of the supramolecular synthons present within the crystals are described. Evidence for improved animal pharmacokinetic data is given for several systems. A summary is provided of our current understanding of the relationship between cocrystal structure and solution phase interactions on solubility as well as those factors that influence overall cocrystal thermodynamic stability.