(â)-Sparteine directed lithiation of N-Boc-pyrrolidine, alkylation with chloromethylboronate pinacol ester and acid-based deprotection provides homoboroproline HX salt in 94% ee, which is then an efficient enamine-type pyrrolidine catalyst in an asymmetric aldol reaction when neutralised and especially when esterified in situ with a tartrate ester, for example, providing 90% ee of the aldol adduct derived from acetone and p-nitrobenzaldehyde.
()-
金雀花碱直接
锂化 N-Boc-
吡咯烷,用
氯甲基
硼酸频哪醇酯进行烷基化,然后进行酸基脱保护,得到 94% ee 的高
硼脯
氨酸 HX 盐,这是不对称羟醛反应中有效的烯胺型
吡咯烷催化剂当中和时,尤其是当用
酒石酸酯原位酯化时,例如,提供90%ee的衍生自
丙酮和
对硝基苯甲醛的羟醛加合物。