Elucidation of the Structure of Pseudorubriflordilactone B by Chemical Synthesis

Abstract

Rubriflordilactone B (1) is a schinortriterpenoid isolated by Sun and colleagues, which possesses a tetrasubstituted benzene moiety and eight stereocenters. The previous synthesis of 1 by Li and co-workers uncovered the existence of its naturally occurring stereoisomer “pseudorubriflordilactone B”. Here we report a collaborative study by the two groups that elucidates the structure of pseudorubriflordilactone B to be 16,17-bis-epi-rubriflordilactone B (26). Chemical synthesis served as an important tool in the structure determination. Taking advantage of a modular synthetic route, we systematically “mutated” the configurations of C-23, C-22, C-20, and C-16/C-17 located at the right-hand domain of 1, and thus prepared its 15 stereoisomers for spectrum comparison. The 1H NMR spectra of synthetic 26 in deuterated chloroform and pyridine were identical to those of authentic pseudorubriflordilactone B, respectively. This synthetic sample displayed anti-HIV activity (EC50 = 0.288 μM) in vitro.

Recent Advance in the Synthesis of Natural Products of Schisandra Triterpenoid

“…李昂小组 [39,40] 采用 6π 电环化 先后于 2014 年和 2016 年分别完成了 rubriflordilactone A 和 rubriflordilactone B 的全合成. 由于 rubriflordi-lactones B 的合成结构与之前分离提出的结构 NMR 数据不 同, 近期, 李昂小组通过化学合成确定了晶体数据和 NMR 数据的对应结构 [54] . 而与此同时 Anderson 小组 [42] 也 [41] [56] .…”

Structural Elucidation of Three 9,11-Seco Tetracyclic Triterpenoids Enables the Structural Revision of Euphorol J

“…4 Plenty examples of the misassignments in triterpenoids have suggested that, besides the routine NMR interpretations, the scrupulous examination of the spectroscopic data by multiple methods, such as computational prediction, coupling constant analysis, and gauche effect analysis, may be an effective way to reduce the probability of the misassignments for those compounds without the crystal structures. 5 In our efforts toward new bioactive metabolites from the Euphorbiaceae species, 6 three rare 9,11-seco tetracyclic triterpenoids (1−3) featuring an enol-hemiacetal moiety were obtained from the whole plants of Euphorbia stracheyi. 1 and 2 represent the first instances of 9,11-seco-euphanes, while 3 is the second example of a 9,11-seco-lanostane (Figure 1).…”

A Unified Strategy to Access Trans-Syn-Fused Drimane Meroterpe-noids: Chemoenzymatic Total Syntheses of Polysin, N-Acetyl-Polyveoline and the Chrodrimanins

“…Drawing inspiration from the syntheses of arene-containing terpenoids by Li and co-workers, 28,29 we sought to construct the central arene ring of the chrodrimanins through a 6p electrocyclization of the corresponding triene precursor. Toward this goal, the C3 alcohol of 11 was temporarily protected as the trimethylsilyl (TMS) ether and the C-ring lactone was converted to the corresponding vinyl triflate (compound 23).…”