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。