A Homodimer of Withaferin A Formed by Base-Promoted Elimination of Acetic Acid from 27-<i>O</i>-Acetylwithaferin A Followed by a Diels–Alder Reaction
作者:E. M. Kithsiri Wijeratne、Ya-Ming Xu、Chayanika Padumadasa、Andrei V. Astashkin、A. A. Leslie Gunatilaka
DOI:10.1021/acs.jnatprod.3c01003
日期:2024.3.22
(2) with the non-nucleophilic base, 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU), afforded 5β,6β-epoxy-4β-hydroxy-1-oxo-witha-2(3),23(24),25(27)-trienolide (3) and 4, a homodimer of withaferin A resulting from a Diels–Alder [4 + 2] type cycloaddition of the intermediate α,β-dimethylene-δ-lactone (9). Structures of 3 and 4 were elucidated using HRMS and 1D and 2D NMR spectroscopic data. The structure of 4
用非亲核碱基 1,8-二氮杂双环[5,4,0]十一碳-7-烯 (DBU) 处理 27- O-乙酰基威瑟林 A ( 2 ),得到 5β,6β-环氧-4β-羟基- 1-oxo-witha-2(3),23(24),25(27)-trienolide ( 3 ) 和4 ,withaferin A 的同二聚体,由中间体 α 的 Diels-Alder [4 + 2] 型环加成反应产生,β-二亚甲基-δ-内酯( 9 )。使用 HRMS 以及一维和二维核磁共振波谱数据阐明了3和4的结构。 4的结构也通过其双-4- O-对硝基苯甲酸酯( 8 )的单晶X射线晶体学分析得到证实。作为主要产物的醉茄素 A 同型二聚体 ( 4 ) 的形成表明了9的 Diels-Alder [4 + 2] 环加成反应的区域选择性和立体选择性。 2-4的乙酰化分别得到它们的乙酰基衍生物5-7 。评估了化合物2 – 4和6 – 8对四种前列腺癌