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Full-Text Articles in Organic Chemistry

Regeneration Of Aged Dmf For Use In Solid-Phase Peptide Synthesis, Jordan K. Magtaan, Marc Devocelle, Fintan Kelleher Nov 2018

Regeneration Of Aged Dmf For Use In Solid-Phase Peptide Synthesis, Jordan K. Magtaan, Marc Devocelle, Fintan Kelleher

Articles

DMF, which is still the most commonly used solvent for Fmoc-SPPS, has the potential for degradation over time on exposure to air (and water vapour) and storage, to give dimethylamine and formic acid impurities. In particular, dimethylamine can lead to unwanted deprotection of the Fmoc group during for example the initial loading of Fmoc amino acids in SPPS, which leads reduced calculated loading values. We have found that treatment of such aged DMF by simple sparging with an inert gas (N2), or vacuum sonication, can regenerate the DMF in order to restore loading levels back to those found for ...


Solid-Phase Peptide Synthesis Of Analogues Of The N-Terminus A-Ring Fragment Of The Lantibiotic Nisin: Replacements For The Dehydroalanine (Dha) Residue At Position 5 And The First Incorporation Of A Thioamide Residue, Kim Manzor, Keith Ó Proinsias, Fintan Kelleher Jun 2017

Solid-Phase Peptide Synthesis Of Analogues Of The N-Terminus A-Ring Fragment Of The Lantibiotic Nisin: Replacements For The Dehydroalanine (Dha) Residue At Position 5 And The First Incorporation Of A Thioamide Residue, Kim Manzor, Keith Ó Proinsias, Fintan Kelleher

Articles

A number of A-ring analogues of the lantibiotic nisin, containing replacements for the Dha at position 5, have been successfully prepared by solid-phase peptide synthesis. The Dha replacements include glycine, alanine, phenylalanine, serine and 1-aminocyclopropyl carboxylic acid (ACCa). The incorporation of a thioamide-isoleucine residue at position 4 is also described and is the first report of the preparation of a lantibiotic ring fragment containing a thioamide link.


Conformational Studies Of Gram-Negative Bacterial Quorum Sensing 3-Oxo N-Acyl Homoserine Lactone Molecules, Darren Crowe, Alan Nicholson, Adrienne Fleming, Ed Carey, Goar Sanchez-Sanz, Fintan Kelleher Jun 2017

Conformational Studies Of Gram-Negative Bacterial Quorum Sensing 3-Oxo N-Acyl Homoserine Lactone Molecules, Darren Crowe, Alan Nicholson, Adrienne Fleming, Ed Carey, Goar Sanchez-Sanz, Fintan Kelleher

Articles

In their 1H NMR spectra in CDCl3 3-oxo-N-acyl homoserine lactones (OHLs) show significant downfield chemical shifts of the amide N-H proton when compared to the parent N-acyl homoserine lactones (AHLs). NMR spectroscopic and DFT calculation studies have shown that this is most likely due to the presence of a stabilising intramolecular H-bond from the N-H to the 3-oxo group. The 1H NMR spectra also show evidence for the enol tautomers and that the amount of enol present for a range of OHLs is 4.1-4.5% in CDCl3 and 6.5-7.2% in ...


Synthesis Of Orthogonally Protected Thioamide Dipeptides For Use In Solid-Phase Peptide Synthesis, Fintan Kelleher, Kim Manzor Nov 2016

Synthesis Of Orthogonally Protected Thioamide Dipeptides For Use In Solid-Phase Peptide Synthesis, Fintan Kelleher, Kim Manzor

Articles

Orthogonally protected thioamide-containing dipeptides were efficiently and cleanly prepared from the precursor dipeptides using Curphey’s method (P4S10, hexamethyldisiloxane (HMDO), reflux, DCM) in 67-96% isolated yield. This was in contrast to the use of Lawesson’s or Berzelius’ reagents where significant issues with reaction non-completion, decomposition and purification were observed. Subsequent clean removal of the dipeptides’ t-butyl ester protecting groups gave thioamide dipeptide acids which were suitable for use in solid-phase peptide synthesis (SPPS).


Bis(Spirolactam) 1,3-Double-Armed Calix[4]Arene Compounds And Their Application As Extractants For The Determination Of Heavy Metal Ions, Fintan Kelleher, Mary Deasy, James Ward, Li Li, Fiona Regan Oct 2015

Bis(Spirolactam) 1,3-Double-Armed Calix[4]Arene Compounds And Their Application As Extractants For The Determination Of Heavy Metal Ions, Fintan Kelleher, Mary Deasy, James Ward, Li Li, Fiona Regan

Articles

A number of double-armed calix[4]arene compounds, with proline-derived spirolactam ligating groups on the lower rim, have been synthesised and investigated as extractants of toxic heavy metal ions from aqueous solution. Pedersen’s extraction technique was employed to determine the capability of these new 1,3-distal derived calix[4]arene spiroalactams to extract selected heavy metal ions (e.g. Pb2+, Cd2+, Zn2+, Cu2+, Ni2+, Co2+) from an aqueous phase into an organic phase. The percentage extraction was calculated using UV-vis spectroscopy. All of the compounds synthesised demonstrated good selectivity for the heavy metals ...


Studies On The Synthesis Of Orthogonally Protected Azalanthionines, And Of Routes Towards B-Methyl Azalanthionines, By Ring-Opening Of N-Activated Aziridine-2-Crboxylates, Keith O'Brien, Keith Ó Proinsias, Fintan Kelleher Jun 2014

Studies On The Synthesis Of Orthogonally Protected Azalanthionines, And Of Routes Towards B-Methyl Azalanthionines, By Ring-Opening Of N-Activated Aziridine-2-Crboxylates, Keith O'Brien, Keith Ó Proinsias, Fintan Kelleher

Articles

Orthogonally protected azalanthionines were successfully synthesised by the ring-opening of N-activated aziridine-2-carboxylates with protected diaminopropanoic acids (DAPs). The required DAPs were also prepared by ring-opening of N-activated aziridine-2-carboxylates with para-methoxybenzylamine, but it was found that the choice of aziridine protecting groups dictated both the success of the reaction as well as the regioselectivity of the isolated products. Attempts to extend the methodology to the preparation of the more sterically demanding b-methyl azalanthionines have, so far, been unsuccessful.


Metal-Organic Frameworks Based On Pyridyl-Tetrazole Ligands Containing Ester Or Carboxylate Pendant Arms, Ursula Sheridan, John Gallagher, Morten Bjerrum, Adrienne Fleming, Fintan Kelleher, John Mcginley May 2014

Metal-Organic Frameworks Based On Pyridyl-Tetrazole Ligands Containing Ester Or Carboxylate Pendant Arms, Ursula Sheridan, John Gallagher, Morten Bjerrum, Adrienne Fleming, Fintan Kelleher, John Mcginley

Articles

The coordination of pyridyl-tetrazole derivatives containing ester substituents, at either the N-1 or N-2 position of the tetrazole ring, with copper(II) chloride results in the formation of either 1:1 or 1:2 copper to ligand complexes, depending on the ligand. However, when the ester functionality is changed to a carboxylate group, the resulting complexation reactions yield metal-organic frameworks. The resulting structures vary dramatically in pore size, depending on both reaction solvents and position of carboxylate group on the tetrazole ring. Despite the presence of sodium cations in the reaction mixtures, no sodium incorporation was ever observed in any ...


Synthesis Of Orthogonally Protected 1,2-Diaminopropanoic Acids By Ring-Opening Of 3-Unsubstituted N-Activated Aziridine 2-Carboxylates With Para-Methoxybenzylamine: A Study Of The Regioselectivity Of The Reaction, Fintan Kelleher, Keith O'Brien Oct 2013

Synthesis Of Orthogonally Protected 1,2-Diaminopropanoic Acids By Ring-Opening Of 3-Unsubstituted N-Activated Aziridine 2-Carboxylates With Para-Methoxybenzylamine: A Study Of The Regioselectivity Of The Reaction, Fintan Kelleher, Keith O'Brien

Articles

Orthogonally protected 1,2-diaminopropanoic acids (DAPs) have been synthesised in good yields by the ring-opening of 3-unsubstituted N-activated aziridine 2-carboxylates with para-methoxybenzylamine. The choice of both the N-activating group and ester alkyl group had a significant influence on the ratio of attack at the a or b positions of the aziridine. However, the regiochemical outcome is not predictable.


Synthesis And Modification Of Octafluoro[2.2]Paracyclophane (Parylene Af4), Craig Hicks, Brendan Duffy, Grainne C. Hargaden Jan 2013

Synthesis And Modification Of Octafluoro[2.2]Paracyclophane (Parylene Af4), Craig Hicks, Brendan Duffy, Grainne C. Hargaden

Articles

Parylenes are a class of organic compounds which have gained significant attention due to their application as coatings in areas such as medical devices and electronics. This review highlights the development of synthetic pathways to Octafluoro[2.2]Paracyclophane, commonly referred to as parylene AF4. Methods which have been used to functionalise AF4 are also presented.


Synthesis Of Orthogonally Protected Azalanthionines (Lanazanines) By Sequential Ring-Opening Of N-Substituted Aziridine 2-Carboxylates, Keith O'Brien, Keith Ó Proinsias, Fintan Kelleher Jan 2013

Synthesis Of Orthogonally Protected Azalanthionines (Lanazanines) By Sequential Ring-Opening Of N-Substituted Aziridine 2-Carboxylates, Keith O'Brien, Keith Ó Proinsias, Fintan Kelleher

Articles

Orthogonally protected azalanthionines (lanazanines, 4-azadiaminopimelic acids or b-aminoalaninoalanines) have been synthesised in good yields by the ring-opening of N-protected aziridine 2-carboxylates with suitably protected diaminopropanoic acids (DAPs). The required DAPs were also synthesised by ring-opening of N-protected aziridine 2-carboxylates with para-methoxybenzylamine.


Structure-Reactivity Studies Of Simple 4-Hydroxyprolinamide Organocatalysts In The Asymmetric Michael Addition Reaction Of Aldehydes To Nitroolefins, Fintan Kelleher, John Watts, Lien Luu, Vickie Mckee, Ed Carey Jan 2012

Structure-Reactivity Studies Of Simple 4-Hydroxyprolinamide Organocatalysts In The Asymmetric Michael Addition Reaction Of Aldehydes To Nitroolefins, Fintan Kelleher, John Watts, Lien Luu, Vickie Mckee, Ed Carey

Articles

A series of simple 4-hydroxyprolinamides was synthesised and they were found to act as organocatalysts for the asymmetric conjugate addition of aldehydes to nitroolefins in excellent yields (98%), with complete diastereoselectivity (99:1, syn:anti) and enantioselectivity (98% e.e. for syn). Furthermore, the use of low catalyst loadings (5 mol%) and a low aldehyde molar excess (1.5 equivalents) were achieved.


Structure-Reactivity Relationships Of L-Proline Derived Spirolactams And A-Methyl Prolinamide Organocatalysts In The Asymmetric Michael Addition Reaction Of Aldehydes To Nitroolefins., Fintan Kelleher, Sinead Kelly, John Watts, Vickie Mckee Jan 2010

Structure-Reactivity Relationships Of L-Proline Derived Spirolactams And A-Methyl Prolinamide Organocatalysts In The Asymmetric Michael Addition Reaction Of Aldehydes To Nitroolefins., Fintan Kelleher, Sinead Kelly, John Watts, Vickie Mckee

Articles

L-Proline derived spirolactams and a-methyl prolinamides act as organocatalysts for the asymmetric conjugate addition of aldehydes to nitroolefins in excellent yields, with good diastereoselectivity and enantioselectivity. Furthermore, low catalyst loadings (5 mol%) and a low aldehyde molar excess (1.5 molar equivalents) were achieved.


Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond Jan 2007

Improved Nitrate Sensing Using Ion Selective Electrodes Based On Urea–Calixarene Ionophores, Benjamin Schazmann, Dermot Diamond

Articles

Urea–calix[4]arenes 1 and 2 were synthesised and incorporated into ISE membranes for assessment as sensors for inorganic anions in water. 1 revealed a strong response to all anions following the Hofmeister selectivity order. For ISEs of 2, the response to a portion of the anion series was suppressed, increasing the margin of selectivity of nitrate over chloride, a common interferant of nitrate in fresh and marine water samples. The performance of ISEs containing 2 was compared to commercially available alkylammonium nitrate ion-exchange salts used for nitrate sensing. Our ISEs performed favourably in terms of sensitivity, linear range ...


Use Of The Mitsunobu Reaction In The Synthesis Of Orthogonally Protected A,B-Diaminopropionic Acids, Fintan Kelleher, Keith Ó Proinsias Jan 2007

Use Of The Mitsunobu Reaction In The Synthesis Of Orthogonally Protected A,B-Diaminopropionic Acids, Fintan Kelleher, Keith Ó Proinsias

Articles

Orthogonally protected a,b-diaminopropionic acids have been synthesised in good yields by the reaction of N-trityl L-serine esters with N-substituted sulfonamides under Mitsunobu reaction conditions (DEAD, PPh3, THF). The best isolated yields were obtained when N-Boc p-toluenesulfonamide was used as the nitrogen nucleophile precursor in the Mitsunobu reaction. Subsequently, the N-trityl group was efficiently replaced with the more stable allyloxycarbonyl (alloc) group.


A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond Jan 2006

A Chloride Selective Calix[4]Arene Optical Sensor Combining Urea Functionality With Pyrene Excimer Transduction, Benjamin Schazmann, Dermot Diamond

Articles

A neutral 2-site chloride selective compound has been developed (3), based on a 1,3- alternate tetrasubstituted calix[4]arene providing a preorganised supramolecular scaffold. The resultant supramolecular cavity is amongst the first to combine urea functional groups bridged with single methylene spacers to pyrene moieties. It combines a naturally and synthetically proven H-bonding system with the elegant ratiometric fluorescent signalling properties of an intramolecular pyrene excimer system, triggered by conformational changes upon anion coordination. The excimer emission of 3 is quenched, with a simultaneous rise in the monomer emission solely by the chloride anion amongst a wide variety of ...


Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond Jan 2006

Development Of A Calix[4]Arene Sensor For Soft Metals Based On Nitrile Functionality, Benjamin Schazmann, Dermot Diamond

Articles

The current work is amongst the first to examine the potential usefulness of the nitrile functional group in potentiometric analytical sensors for soft metals. Nitrile functionality has hereby been incorporated into a calix[4]arene skeleton to give a series of new cation selective hosts. The analytical sensing behaviour of these hosts was examined by Ion Selective Electrode (ISE) based potentiometry. In all cases a preference for soft metals was observed, explained primarily in terms of soft–soft compatibility between calix[4]arene nitrile hosts and metal guests in combination with a classical ‘lock and key’ best fit mechanism. Hosts ...


Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly Jan 2006

Spirobicyclic Diamines 2: Synthesis Of Homochiral Diastereoisomeric Proline Derived [4,4]-Spirolactams, Fintan Kelleher, Sinead Kelly

Articles

L-Proline derived diastereoisomeric [4.4]-spirolactams have been prepared by a reductive-amination reaction of (R)- or (S)-alanine methyl ester followed by thermal cyclisation of the resulting amine onto the proline ester group in refluxing toluene. Under similar conditions (R)- or (S)-phenylalanine methyl ester gave no cyclisation products, while R- or S-a-methylbenzylamine required treatment with NaNH2 in refluxing toluene to induce cyclisation giving diastereoisomeric [4.4]-spirolactams


Identification And Recovery Of An Asymmetric Calix[4]Arene Tetranitrile Derivative Using Liquid Chromatography And Mass Spectrometry, Benjamin Schazmann, Dermot Diamond Jan 2005

Identification And Recovery Of An Asymmetric Calix[4]Arene Tetranitrile Derivative Using Liquid Chromatography And Mass Spectrometry, Benjamin Schazmann, Dermot Diamond

Articles

A simple analytical LC-MS (Liquid Chromatography Mass Spectrometry) method and associated instrumentation has been adapted for use by the organic chemist to yield mg quantities of target compound from a reaction mixture. Calix[4]arene 3 was identified as representing 51% of total peak area of a reaction mixture containing no less than 10 components, using LC-MS. This peak corresponded to a mass of 878.8, equivalent to a complex of 3 and an ammonium cation. Molecular models further rationalise this observation by showing that the asymmetric binding cavity of 3 is suitable for binding tetrahedral guests like the ammonium ...