Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 17.1 Preparation of aliphatic amino acid derived γ-alkoxycarbonylamino-β-oxo ylides and pyrolysis to give α,β-acetylenic γ-amino acid and GABA analogues
Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 17.1 Preparation of aliphatic amino acid derived γ-alkoxycarbonylamino-β-oxo ylides and pyrolysis to give α,β-acetylenic γ-amino acid and GABA analogues
Convenient synthesis of chiral α,β-acetylenic γ-amino acid derivatives and γ-aminobutyric acid analogues via stabilized ylides
作者:R. Alan Aitken、Nzaira Karodia
DOI:10.1039/cc9960002079
日期:——
Twelve examples of protected acetylenic amino acids are readily prepared in a two-step procedure involving formation and flash vacuum pyrolysis of chiral aminoacyl phosphorus ylides.
Flash vacuum pyrolysis of stabilised phosphorus ylides. Part 17.1 Preparation of aliphatic amino acid derived γ-alkoxycarbonylamino-β-oxo ylides and pyrolysis to give α,β-acetylenic γ-amino acid and GABA analogues
作者:R. Alan Aitken、Nazira Karodia、Tracy Massil、Robert J. Young
DOI:10.1039/b110243e
日期:2002.2.6
A series of eleven α-aminoacyl stabilised phosphorus ylides 9â19 have been prepared by condensation of N-alkoxycarbonyl protected amino acids with Ph3PCHCO2Et using a carbodiimide peptide coupling reagent. Upon flash vacuum pyrolysis at 600 °C, these undergo extrusion of Ph3PO to give the corresponding α,β-acetylenic γ-amino esters 21â29, 33 and 34 in moderate yield. In two cases the terminal alkynes 30 and 31 are also formed. The β-aminoacyl ylide 20 from β-alanine
similarly gives the α,β-acetylenic δ-amino ester 35 upon pyrolysis. Regioselective addition of HBr to the triple bond of one acetylenic ester 25 was observed giving a mixture of E and Z
α-bromoacrylates 36. Hydrogenation of the N-Cbz acetylenic esters 21â23 and 33 results in N-deprotection and hydrogenation of the triple bond to afford the chiral GABA analogues 37â40 in 70 â>95% ee as determined by 19F NMR of their Mosher amides. Fully assigned 13C NMR spectra of all the ylides and acetylenic ester derivatives are presented.