233757-75-0Relevant academic research and scientific papers
Intramolecular nitrone dipolar cycloadditions: Control of regioselectivity and synthesis of naturally-occurring spirocyclic alkaloids
Hodges, Alastair J.,Bond, Andrew D.,Holmes, Andrew B.,Roughley, Stephen D.,Smith, Catherine J.,Adams, Joseph P.,Ryan, John H.,Saubern, Simon,Newton, Annabella F.,Press, Neil J.,Turnbull, Michael D.
supporting information, p. 8963 - 8974,12 (2012/12/12)
The intramolecular nitrone dipolar cycloaddition of in situ-generated nitrones such as compound 26 has been used for the synthesis of cyclic isoxazolidines 27 and 29. The regioselectivity of the intramolecular cycloaddition depends on the nature of the terminal substituent on the dipolarophile. The influence of the substituent on the regioselectivity of the cycloaddition has been examined using several model systems and two methods of nitrone formation. These studies demonstrated that the cyano-substituent plays a special role in favouring the formation of the 6,6,5-ring fused adduct 27 under thermodynamically controlled conditions. The utility of the cyclo-adduct 57 (see Scheme 12) as a precursor for the naturally occurring histrionicotoxins is illustrated by the synthesis of three "unsymmetrical" (i.e. with each side chain bearing different functional groups) members of the histrionicotoxin family HTX-259A, HTX-285C and HTX-285E (2, 3 and 4 respectively).
Intramolecular nitrone dipolar cycloadditions: Control of regioselectivity and synthesis of naturally-occurring spirocyclic alkaloids
Hodges, Alastair J.,Adams, Joseph P.,Bond, Andrew D.,Holmes, Andrew B.,Press, Neil J.,Roughley, Stephen D.,Ryan, John H.,Saubern, Simon,Smith, Catherine J.,Turnbull, Michael D.,Newton, Annabella F.
supporting information, p. 8963 - 8974 (2013/01/15)
The intramolecular nitrone dipolar cycloaddition of in situ-generated nitrones such as compound 26 has been used for the synthesis of cyclic isoxazolidines 27 and 29. The regioselectivity of the intramolecular cycloaddition depends on the nature of the terminal substituent on the dipolarophile. The influence of the substituent on the regioselectivity of the cycloaddition has been examined using several model systems and two methods of nitrone formation. These studies demonstrated that the cyano-substituent plays a special role in favouring the formation of the 6,6,5-ring fused adduct 27 under thermodynamically controlled conditions. The utility of the cyclo-adduct 57 (see Scheme 12) as a precursor for the naturally occurring histrionicotoxins is illustrated by the synthesis of three "unsymmetrical" (i.e. with each side chain bearing different functional groups) members of the histrionicotoxin family HTX-259A, HTX-285C and HTX-285E (2, 3 and 4 respectively).
Nitrone dipolar cycloaddition routes to piperidines and indolizidines. Part 9. Formal synthesis of (-)-pinidine and total synthesis of (-)-histrionicotoxin, (+)-histrionicotoxin and (-)-histrionicotoxin 235A
Davison, Edwin C.,Fox, Martin E.,Holmes, Andrew B.,Roughley, Stephen D.,Smith, Catherine J.,Williams, Geoffrey M.,Davies, John E.,Raithby, Paul R.,Adams, Joseph P.,Forbes, Ian T.,Press, Neil J.,Thompson, Mervyn J.
, p. 1494 - 1514 (2007/10/03)
An intramolecular hydroxylamine-alkyne cyclisation is used for the enantioselective synthesis of the cyclic nitrones 36 and 44. We have demonstrated the use of a novel nitrone protection strategy by cycloaddition of styrene to the cyclic nitrone 44 in the synthesis of the spirocyclic core of the histrionicotoxin family of alkaloids. Deprotection by dipolar cycloreversion of the styrene adduct (the bicyclic isoxazolidine 39) and in situ intramolecular dipolar cycloaddition of a pendant (Z)-α,β-unsaturated nitrile to the intermediate nitrone 50 gave the isoxazolidine 51 in high yield with a surprising degree of regioselectivity compared with the corresponding (Z)-enyne 36. The method is amenable to the synthesis of both enantiomers 51 and 62 of the tricyclic core structure which can be converted by way of the common intermediates (e.g. 53 and ent-53) respectively into the natural configuration of alkaloids (-)-histrionicotoxin 1 and (-)-histrionicotoxin 235A 65 as well as the unnatural (+)-histrionicotoxin 63.
