δ-Lactone formation from δ-hydroxy-trans-α,β-unsaturated carboxylic acids accompanied by trans–cis isomerization: synthesis of (−)-tetra-O-acetylosmundalin
作者:Machiko Ono、Xi Ying Zhao、Yuki Shida、Hiroyuki Akita
DOI:10.1016/j.tet.2007.07.106
日期:2007.10
E)-hexenoic acid 6 was subjected to δ-lactonization in the presence of 2,4,6-trichlorobenzoyl chloride and pyridine to give the α,β-unsaturated-δ-lactone congener (±)-7 (87% yield) accompanied by trans–cis isomerization. This δ-lactonization procedure was applied to the chiral synthesis of (+)-(4S,5R)-7 or (−)-(4R,5S)-7 from the chiral starting material (+)-(4S,5R)-6 or (−)-(4R,5S)-6. Deprotection
在2,4,6-三氯苯甲酰氯和吡啶存在下,将(±)-(4,5-抗)-4-苄氧基-5-羟基-(2 E)-己酸6进行δ-内酯化,得到α,β-不饱和-δ-内酯同类物(±)-7(87%收率)伴随反式-顺式异构化。这个δ-内酯化过程应用于(+)的手性合成- (4-小号,5 - [R )- 7或( - ) - (4 - [R,5小号) - 7从手性原料(+) - (4- S,5 R)-6或(-)-(4 R,5 S)-6。在(+)苄基的脱保护- (4小号,5 - [R )- 7或( - ) - (4 - [R,5小号) - 7通过的AlCl 3 /中号二甲苯系统得到自然osmundalactone(+) - (4 S,5 R)-5或(-)-(4 R,5 S)-5分别具有良好的收率。在BF 3 ·Et 2存在下,(-)-(4 R,5 S)-5和四乙酰基-β-d-葡萄糖基三氯亚氨酸酯22的缩合O提供的缩合产物(-)-