Addition of 2-Lithiofuran to Chiral α-Alkoxy Nitrones; a Stereoselective Approach to α-Epimeric β-Alkoxy-α-amino Acids
作者:A. Dondoni、F. Junquera、F. L. Merchan、P. Merino、T. Tejero
DOI:10.1055/s-1994-25712
日期:——
The addition of 2-lithiofuran (1) to the N-benzyl nitrones 2a-d, derived from chiral α-alkoxy aldehydes, affords β-alkoxy-α-hydroxyamino-2-alkylfurans in good yields and with syn selectivity. Conversely, the reaction with the same nitrones precomplexed with diethylaluminum chloride leads to the same adducts but with anti selectivity. Three pairs of epimeric hydroxylamines are subjected to reductive N-dehydroxylation with titanium(III) chloride and then to furyl-carboxylic acid conversion with ruthenium tetroxide to give the corresponding α-epimeric β-alkoxy-α-amino acids.
将 2-锂硫呋喃 (1) 添加到衍生自手性 α-烷氧基醛的 N-苄基硝酮 2a-d 中,以良好的产率和顺式选择性提供 β-烷氧基-α-羟基氨基-2-烷基呋喃。相反,与与二乙基氯化铝预络合的相同硝酮的反应产生相同的加合物,但具有反选择性。三对差向异构羟胺用氯化钛(III) 进行还原性N-脱羟基,然后用四氧化钌进行呋喃基-羧酸转化,得到相应的α-差向异构β-烷氧基-α-氨基酸。