N,O-Acetals from Pivalaldehyde and Amino Acids for the ?-Alkylation with Self-Reproduction of the Center of Chirality. Enolates of 3-Benzoyl-2-(tert-butyl)-1,3-oxazolidin-5-ones
作者:Dieter Seebach、Antoine Fadel
DOI:10.1002/hlca.19850680521
日期:1985.8.14
The sodium salts of (S)-alanine, (S)-phenylalanine, (S)-valine, and (S)-methionine are condensed with pivalaldehyde to imines 5. Cyclization by treatment with benzoyl chloride in cold CH2Cl2 gives mainly (4:1 to > 99:1) the (2S,4S)-4-alkyl-3-benzoyl-2-(tert-butyl)-1,3-oxazolidin-5-ones (6; cis-configuration) in high yields (85–95%). The oxazolidinones 6 and 7 are deprotonated with lithium diethylamide
(S)-丙氨酸,(S)-苯丙氨酸,(S)-缬氨酸和(S)-蛋氨酸的钠盐与新戊醛缩合成亚胺5。通过在冷的CH 2 Cl 2中用苯甲酰氯处理进行环化,主要得到(4:1至> 99:1)(2 S,4 S)-4-烷基-3-苯甲酰基-2-(叔丁基)-1 ,3-恶唑烷-5-酮(6;顺式构型)高产(85–95%)。恶唑烷酮6和7用二乙氨基锂(LDEA)在四氢呋喃(THF)中进行质子化,烷基化(Mel,苄基溴)或羟烷基化(苯甲醛)分别以高非对映选择性(9:1至50:1 )分别形成4,4-二取代的恶唑烷酮9和10。 ;相对话题性ul)。三种恶唑烷酮水解为已知构型和光学纯度的氨基酸表明,在该过程中很少发生外消旋作用。