Co-reporter:Graham Stones, Régis Tripoli, Colin L. McDavid, Kewin Roux-Duplâtre, Alan R. Kennedy, David C. Sherrington and Colin L. Gibson
Organic & Biomolecular Chemistry 2008 vol. 6(Issue 2) pp:374-384
Publication Date(Web):11 Dec 2007
DOI:10.1039/B716938H
Two routes to the synthesis of a cyclohexyl-fused 1,4,7-triazacyclononane involving macrocyclisations of tosamides have been investigated. In the first approach, using a classic Richman–Atkins-type cyclisation of a cyclohexyl-substituted 1,4,7-tritosamide with ethylene glycol ditosylate, afforded the cyclohexyl-fused 1,4,7-triazacyclononane in 5.86% overall yield in four steps. The second, more concise, approach involving the macrocyclisation of trans-cyclohexane-1,2-ditosamide with the tritosyl derivative of diethanolamine initially gave poor yields (< 25%). The well-documented problems with efficiencies in macrocyclisations using 1,2-ditosamides led to the use of a wider range of 1,2-ditosamides including ethane-1,2-ditosamide and propane-1,2-ditosamide. These extended studies led to the development of an efficient macrocyclisation protocol using lithium hydride. This new method afforded 1,4,7-tritosyl-1,4,7-triazacyclononanes in good yield (57–90%) from 1,2-ditosamides in a single step. These efficient methods were then applied to the preparation of a chiral cyclohexyl-fused 1,4,7-tritosyl-1,4,7-triazacyclononane (65–70%). This key chiral intermediate was then converted into a copper(II) complex following detosylation and N-methylation. The resulting chiral copper(II) complex catalysed the aziridination of styrene but it did so in a racemic fashion.
Co-reporter:Gilles Argouarch, Graham Stones, Colin L. Gibson, Alan R. Kennedy and David C. Sherrington
Organic & Biomolecular Chemistry 2003 vol. 1(Issue 24) pp:4408-4417
Publication Date(Web):06 Nov 2003
DOI:10.1039/B310492C
Three chiral 2,6-disubstituted tri-N-methyl azamacrocycles have been prepared by modular methods. These macrocycles were accessed from three chiral 1,4,7-triazaheptanes intermediates that were prepared by two independent routes. The first of these routes involved the benzylamine opening of chiral tosyl aziridines followed by debenzylation but was problematic on solubility grounds. A second, more effective, route was developed which avoided debenzylation by using ammonia in the nucleophilic opening of chiral tosyl aziridines.
Co-reporter:Graham Stones, Gilles Argouarch, Alan R. Kennedy, David C. Sherrington and Colin L. Gibson
Organic & Biomolecular Chemistry 2003 vol. 1(Issue 13) pp:2357-2363
Publication Date(Web):22 May 2003
DOI:10.1039/B302887A
Using L-valine methyl ester hydrochloride as starting material, the synthesis of (2S)-2-isopropyl-1,4,7-trimethyl-1,4,7-triazacyclononane is described. Various standard Richman–Atkins cyclisation methods gave only poor yields in the key macrocyclisation step. Efficient macrocyclisation yields were, however, realised when an in situ sequential cyclisation method was developed.
Co-reporter:Karen Alexander (née Gillon), Stuart Cook, Colin L. Gibson and Alan R. Kennedy
Organic & Biomolecular Chemistry 2001 (Issue 13) pp:1538-1549
Publication Date(Web):08 Jun 2001
DOI:10.1039/B102020J
A series of three 5,5-diaryl substituted oxazolidin-2-ones (diphenyl, dinaphthyl and ditolyl) have been synthesised. Studies on the benzylation of the lithium enolates of N-acyl derivatives reveal that the yields obtained were sensitive to the method of quenching the reaction. This was particularly acute for the 5,5-diphenyl system where effective yields (69%) and high diastereoselectivities (dr 98 ∶ 2) are only observed when the reactions were quenched into aqueous buffer. Methylation studies on the N-acyl derivatives showed that the most advantageous results (58–69%, dr 91 ∶ 9) were only observed using the sodium enolates. The 5,5-ditolyl-4-isopropyloxazolidin-2-one proved to be more efficacious in terms of efficiency and diastereoselectivity (dr 97 ∶ 3). Subsequent, simple alkaline hydrolyses of the alkylation products allowed for the high
recovery and recyclability of the 5,5-diaryl substituted oxazolidin-2-ones without any deleterious endocyclic cleavage. In addition, the acyl portions were recovered in high yield from the alkaline hydrolyses without any evidence of racemisation.
Co-reporter:Colin L. Gibson, Sheetal Handa
Tetrahedron: Asymmetry 1996 Volume 7(Issue 5) pp:1281-1284
Publication Date(Web):May 1996
DOI:10.1016/0957-4166(96)00144-9
The synthesis of the naturally occurring 2(5H)-furanone (R)-(+)-umbelactone 1 in five steps and 26.2% overall yield from acid 2 is describedThe natural product (R)-(+)-umbelactone 1 has been synthesised in 5 steps and 26.2% overall yield from (2S)-2,3-dihydroxy-(2,3-O-isopropylidene)propanoic acid 2.
Co-reporter:Graeme A. Cran, Colin L. Gibson, Sheetal Handa
Tetrahedron: Asymmetry 1995 Volume 6(Issue 7) pp:1553-1556
Publication Date(Web):July 1995
DOI:10.1016/0957-4166(95)00197-W
Bifurcated routes to two series of chiral secondary ß-amino sulfides 5a - c and 11a - c have been developed from L-proline and (S)-phenylglycine, respectively. The developed methodology has also led to the synthesis of the tertiary ß-amino thiol 7 and the primary ß-amino sulfide 12 from L-proline and (S)-phenylglycine, respectively.Two sets of chiral ß-amino sulfides were prepared from L-proline and (S)-phenylglycine. A tertiary ß-amino thiol was also synthesised from L-proline.
Co-reporter:Graham Stones, Régis Tripoli, Colin L. McDavid, Kewin Roux-Duplâtre, Alan R. Kennedy, David C. Sherrington and Colin L. Gibson
Organic & Biomolecular Chemistry 2008 - vol. 6(Issue 2) pp:NaN384-384
Publication Date(Web):2007/12/11
DOI:10.1039/B716938H
Two routes to the synthesis of a cyclohexyl-fused 1,4,7-triazacyclononane involving macrocyclisations of tosamides have been investigated. In the first approach, using a classic Richman–Atkins-type cyclisation of a cyclohexyl-substituted 1,4,7-tritosamide with ethylene glycol ditosylate, afforded the cyclohexyl-fused 1,4,7-triazacyclononane in 5.86% overall yield in four steps. The second, more concise, approach involving the macrocyclisation of trans-cyclohexane-1,2-ditosamide with the tritosyl derivative of diethanolamine initially gave poor yields (< 25%). The well-documented problems with efficiencies in macrocyclisations using 1,2-ditosamides led to the use of a wider range of 1,2-ditosamides including ethane-1,2-ditosamide and propane-1,2-ditosamide. These extended studies led to the development of an efficient macrocyclisation protocol using lithium hydride. This new method afforded 1,4,7-tritosyl-1,4,7-triazacyclononanes in good yield (57–90%) from 1,2-ditosamides in a single step. These efficient methods were then applied to the preparation of a chiral cyclohexyl-fused 1,4,7-tritosyl-1,4,7-triazacyclononane (65–70%). This key chiral intermediate was then converted into a copper(II) complex following detosylation and N-methylation. The resulting chiral copper(II) complex catalysed the aziridination of styrene but it did so in a racemic fashion.