Synthesis of γ- and δ-Lactone Natural Products by Employing a trans–cis Isomerization/Lactonization Strategy
作者:Machiko Ono、Keisuke Kato、Hiroyuki Akita
DOI:10.1248/cpb.c12-01026
日期:——
Alkaline hydrolysis of 4-hydroxy- or/and 5-hydroxy-(2E)-alkenoate followed by acid treatment gave the corresponding (2E)-alkenoic acids which were subjected to lactone formation reaction without further purification. The crude acids were treated with 2,4,6-trichlorobenzoyl chloride in pyridine to afford γ-lactone or δ-lactone, respectively, accompanied by trans–cis isomerization. By this procedure, (±)-(4,5)-trans-5-benzyloxy-2-hexen-4-olide (90% overall yield), (S)-5-hydroxy-2-penten-4-olide (86% overall yield), (4S,5R)-5-hydroxy-2-hexen-4-olide (86% overall yield), (4R,5S)-5-hydroxy-2-hexen-4-olide (82% overall yield), (S)-parasorbic acid (58% overall yield) and natural product, (5R,7S)-7-hydroxy-2-octen-5-olide (euscapholide: 20% overall yield) were synthesized.
4-羟基或/和5-羟基-(2E)-烯酸盐的碱性水解后进行酸处理,得到了相应的(2E)-烯酸,然后未经过进一步纯化直接进行内酯形成反应。粗酸与2,4,6-三氯苯甲酰氯在吡啶中反应,分别生成γ-内酯或δ-内酯,并伴随有反-顺异构化。通过这种方法合成了(±)-(4,5)-反-5-苄氧基-2-己烯-4-内酯(整体产率90%)、(S)-5-羟基-2-戊烯-4-内酯(整体产率86%)、(4S,5R)-5-羟基-2-己烯-4-内酯(整体产率86%)、(4R,5S)-5-羟基-2-己烯-4-内酯(整体产率82%)、(S)-伐索酸(整体产率58%)以及天然产物(5R,7S)-7-羟基-2-辛烯-5-内酯(优蔬内酯:整体产率20%)。