Department of Chemistry, WestChem, University of Glasgow, Glasgow G12 8QQ, UK.
J Org Chem. 2009 Nov 6;74(21):8425-7. doi: 10.1021/jo9016293.
The selective N-methylation of BOC-protected valine 1a with MeI and NaH in THF (i.e., in the presence of a free carboxyl group) has been attributed to the protection of the carboxylate by chelation to Na(+). An alternative mechanism, involving the formation of the carbene intermediate generated from MeI and its insertion into the N-H bond, has been ruled out by isotopic labeling.
BOC-保护的缬氨酸 1a 在 THF 中与 MeI 和 NaH 的选择性 N-甲基化（即在存在游离羧基的情况下）归因于通过与 Na(+)螯合来保护羧酸盐。通过同位素标记排除了涉及由 MeI 生成的卡宾中间体的形成及其插入 N-H 键的替代机制。
