Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
Org Lett. 2012 Feb 17;14(4):968-71. doi: 10.1021/ol203088g. Epub 2012 Feb 8.
A streamlined entry into the sesquiterpene lactone (SQL) cores of linearifolin and zaluzanin A is described. Stereochemistry is controlled through transformations uncovered by ISES (In Situ Enzymatic Screening). Absolute stereochemistry derives from kinetic resolution of 5-benzyloxypentene-1,2-oxide, utilizing a β-pinene-derived-Co(III)-salen. Relative stereochemistry (1,3-cis-fusion) is set via formal halometalation/carbocyclization, mediated by Rh(O(2)CC(3)F(7))(2)/LiBr. Subsequent ring-closing metathesis (RCM-Grubbs II) yields the title exomethylene-δ-lactone SQL cores. In complementary fashion, RCM with Grubbs-I catalyst provides the oxabicyclo[3.3.1]nonyl core of xerophilusin R and zinagrandinolide.
描述了一种简化进入倍半萜内酯（SQL）核心的方法，包括线性呋喃和扎鲁扎宁 A。立体化学通过 ISES（原位酶筛选）揭示的转化来控制。绝对立体化学来自于通过利用β-蒎烯衍生的 Co(III)-salen 对 5-苯氧戊烯-1,2-氧化物进行动力学拆分得到。相对立体化学（1,3-顺式融合）是通过Rh(O(2)CC(3)F(7))(2)/LiBr 介导的卤化/环化来设定的。随后的闭环复分解（RCM-Grubbs II）得到标题的外亚甲基-δ-内酯 SQL 核心。以互补的方式，用 Grubbs-I 催化剂进行 RCM 提供了 Xerophilusin R 和 Zinagrandinolide 的氧杂双环[3.3.1]壬烷核心。
