Hydrogen-bond landscapes, geometry and energetics of squaric acid and its mono- and dianions: a Cambridge Structural Database, IsoStar and computational study

Allen, Frank H.; Cruz‐Cabeza, Aurora J.; Wood, Peter A.; Bardwell, David A.

doi:10.1107/s2052519213020277

Cited by 9 publications

(7 citation statements)

References 48 publications

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“…The extension of the investigation to the synthesis of squaraines by reacting S3 or S4 and 1I under mechanical milling activation afforded squaraine 4 in extremely low yield (<15 %, Table S1). We believe that squaric acid shows a very low reactivity under mechanical milling activation likely because mechanical energy provided may not be sufficient to overcome its strong intermolecular interactions in the solid state [9c] …”

Section: Resultsmentioning

confidence: 99%

Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation

et al. 2021

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Squaraines and croconaines are organic dyes characterized by intense absorption in the visible or near‐infrared spectral regions with applications ranging from biology to material sciences. They are commonly synthesized by condensation reactions of oxocarbonic acids (squaric or croconic acid, respectively) with electron‐rich aromatic compounds in high‐boiling organic solvents. Here, a simple, cost‐effective, and environmentally benign process was developed for the synthesis of indolenine‐based squaraines and croconaines under solvent‐free conditions. Protocols based on conventional thermal heating, mechanochemical milling, and IR‐light activation were compared.

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Section: Resultsmentioning

confidence: 99%

Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation

et al. 2021

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“…All three species possess a certain degree of delocalization, but it is most pronounced in the dianion which is considered to be aromatic. [18][19][20][21][22][23] Figure 3. Squaric acid and its mono-and dianion.…”

Section: Squaric Acid and Oxocarbones -Characteristicsmentioning

confidence: 99%

A concise review on application of squaric acid derivatives and their metal complexes in medicine

Bakalova¹,

Ruseva²,

Cherneva³

2022

Arkivoc

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In this review, we summarize the data about applications of squaric acid, its derivatives and their metal complexes in medicine. In recent years, researchers have been concentrated on the study of squaric acid and its derivatives because of their unique properties and the different possible ways to coordinate with metals and form complex compounds. Encouraging results have also been obtained for the cytotoxic activity of some squaric acid analogues and their metal complexes on various human tumor cell lines.

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“…These cyclic oxocarbon anions are members of an aromatic series -(Hückel's rule for monocyclic systems) -stabilised by the delocalization of electrons around the carbon ring [57]. The monocyclic oxocarbon family (Figure 4) include the following:…”

Section: Oxocarbonsmentioning

confidence: 99%

“…The squaramide contains a dipole, possssing a partial negative charge on the carbonyls and a partial positive charge on the nitrogen. The dipole is a contribution from the canonical forms [57].…”

Section: Squaryl Amino Acidsmentioning

confidence: 99%

Squaryl Molecular Metaphors – Application to Rational Drug Design and Imaging Agents

Kitson¹

2017

J Diagn Imaging Ther

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Molecular Metaphors is the application of squaryl building blocks towards creative functional group chemistry to produce lead compounds and imaging agents. This strategy is applied to rational drug design and to various imaging agents that would normally contain conventional functional group chemistry. These, include carboxylic acids, α-amino acids, peptide bonds and phosphonates. Moreover, the squaryl metaphor is a precursor to complex organic molecules involving functional group interchange (FGI) and rearrangements. This article discusses the application of these metaphors in the area of neurochemistry, especially NMDA receptors. An important area of drug design is the inhibition of angiotensin II enzyme by the use of losartan. This commercial drug contains a tetrazole moiety that can be modified using the squaryl group to give a semisquarate derivative. These concepts can extend to the semisquarate of ibuprofen. Moreover, a discussion on peptidomimetics regarding the substitution of the peptide bond for squaramide allows for a change in the biological properties due to modification at the peptide bond. Furthermore, the topic on how squaryl metaphors can be exploited primarily by the central 1,3-hydroxyamide sequence to the generation of a novel class of HIV protease inhibitors. Also, squaryl metaphors can be used to develop potential inhibitors of glutathione and novel anti-migraine drugs. The discussion continues on the design of anticancer drugs: in particular, a novel class of metalloproteases, including phosphonates for semisquaramides, leading to squaryl nucleosides. This review concludes with the application of squaryl metaphors in the design of positron emission tomography (PET) and magnetic resonance imaging (MRI) agents towards theranostics. describe the ability of individual functional chemical groups to mimic other moieties [2,3]. KeywordsErlenmeyer rationalised these concepts and categorised isosteres into atoms, ions and molecules based on the valence level of electrons [4]. A further understanding by Friedman led to the term bioisosterism to include all atoms and molecules that fit the broadest definition of isosteres [5]. This approach was independent of whether the drug was an agonist or an antagonist towards biological activity.Moreover, Thornber applied the term bioisosterism to include subunits, groups or molecules that possess physicochemical properties of similar biological effects [6]. Finally, in 1991 Burger widened the definition of bioisosteres to include compounds or groups that possess similar molecular shapes and volumes independent of agonists or antagonists [7]. REVIEW ARTICLE Squaryl KitsonThese bioisosteres would require approximately the same distribution of electrons and give a high probability of generating comparable physical properties such as hydrophobicity [8]. Currently, bioisosterism is one of the most useful tools to the medicinal chemist in rational drug design and in particular regarding the carboxylic acid bioisosteres [9]. The carboxylic acid functional ...

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Hydrogen-bond landscapes, geometry and energetics of squaric acid and its mono- and dianions: a Cambridge Structural Database, IsoStar and computational study

Cited by 9 publications

References 48 publications

Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation

Solvent‐free Reactions for the Synthesis of Indolenine‐based Squaraines and Croconaines: Comparison of Thermal Heating, Mechanochemical Milling, and IR Irradiation

A concise review on application of squaric acid derivatives and their metal complexes in medicine

Squaryl Molecular Metaphors – Application to Rational Drug Design and Imaging Agents

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