A PRACTICAL METHOD FOR THE ACYLATION OF 2-IMIDAZOLIDINONE AND 2-OXAZOLIDINONE CHIRAL AUXILIARIES WITH 2- BROMOACYL HALIDES
作者:Sara X. Candeias、Kerry Jenkins、A. S. C. Ribeiro、Carlos A. M. Afonso、Stephen Caddick
DOI:10.1081/scc-100106033
日期:2001.1
Optimised conditions for the acylation of (S)-4-(1-methylethyl) -oxazolidin-2-one 4, (R)-4-phenyloxazolidin-2-one 5 and 4-(R), (5S)-1,5-dimethyl-4-phenylimidazolidin-2-one 3 with 2-bromoacyl halides were developed. For imidazolidin-2-one 3 the optimum conditions require the use of the hindered bases2,6-di-t-butylpyridine or 2,6-lutidine in order to reduce the ketene formation which has a strong preference for O-acylation.
syn-Selective boron mediated aldol condensations for the asymmetric synthesis of β-hydroxy-α-amino acids
作者:S Caddick、N.J Parr、M.C Pritchard
DOI:10.1016/s0040-4039(00)00734-6
日期:2000.7
Imidazolidinone-bound glycine enolate derivatives have been shown to undergo aldol condensation with aromatic and aliphatic aldehydes in good yields and with excellent stereocontrol (62-84%, 93-95% d.e.). Removal of the pendant imidazolidinone auxiliary and hydrogenolysis affords the beta-hydroxy-alpha-amino acid derivatives. (C) 2000 Elsevier Science Ltd. All rights reserved.