New reactivities of deltaline analogs: an efficient O-demethylation at C-1 and an unusual extrusion of the C-14 atom

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• 作者：Pei Tang ; Qi-Feng Chen ; Ling Wang ; Qiao-Hong Chen ; Xi-Xian Jian ; Feng-Peng Wang ; ^{wfp@scu.edu.cn}
• 关键词：C19-Diterpenoid alkaloids ; Deltaline ; O-Demethylation ; Extrusion
• 刊名：Tetrahedron
• 出版年：2012
• 期刊代码：107_00404020
• 类别：ch
• 出版时间：8 July, 2012
• 卷：68
• 期：27-28
• 页码：5668-5676
• 文件大小：771 K

摘要

O-Demethylation at C-1 in the C₁₉-diterpenoid alkaloids is very challenging. In this paper, it was firstly observed that 10-OH group in deltaline (1) is a determining factor for the O-demethylation reaction. After removal of this hydroxyl group, 1-O-methyl group in the corresponding deltaline analogs can be readily removed by treatment with HBr-HOAc. Meanwhile, the C-14 atom in bromides 18 or 20 can be extruded under basic condition probably via a sequence, including Grob fragmentation, aerobic oxidation, deformylation, and S_N2 nucleophilic substitution, to give enone 21 (70%) and oxetane 22 (14%). The structure of compound 22 was confirmed by X-ray crystallographic analysis of its derivative 21.