Identification of an unexpected 2-oxonia[3,3]sigmatropic rearrangement/aldol pathway in the formation of oxacyclic rings. Total synthesis of (+)-aspergillin PZ
摘要:
This paper reports the first unambiguous evidence that the cascade synthesis of tetrahydrofuran-containing oxacyclic molecules depicted in Scheme 12 can take place by a 2-oxonia[3,3]sigmatropic/aldol mechanism rather than by a Prins cyclization/pinacol rearrangement sequence. The 8-oxabicyclo [3.2.1]octyl aldehyde products of this reaction, 20 and 29, were employed to complete the first total synthesis of the structurally remarkable isoindolone alkaloid (+)-aspergillin PZ (1). The lack of activity seen in two tumor cell lines for synthetic (+)-aspergillin PZ calls into question the suggestion that aspergillin PZ, like many aspochalasin diterpenes, might exhibit useful antitumor properties. (C) 2011 Elsevier Ltd. All rights reserved.
in totalsynthesis. We thus describe the synthesis of a putative biomimetic tetracyclic intermediate. The constructive steps are an intramolecular Diels–Alder reaction to install the isoindolone core of cytochalasins, whose branched precursor was obtained from a stereoselective Ireland–Claisenrearrangement performed from a highly unsaturated substrate. This also constitutes a formal synthesis of trichoderone
Aspochalasins 是亮氨酸衍生的细胞松弛素。它们的复杂性与高度的生物合成氧化有关,在此启发了全合成中的两相策略。因此,我们描述了推定的仿生四环中间体的合成。建设性步骤是分子内 Diels-Alder 反应,以安装细胞松弛素的异吲哚酮核心,其分支前体是从高度不饱和底物进行的立体选择性爱尔兰 - 克莱森重排中获得的。这也构成了木霉酮 A 的正式合成。
Multifaceted Study on a Cytochalasin Scaffold: Lessons on Reactivity, Multidentate Catalysis, and Anticancer Properties
intramolecular Diels–Alder (IMDA) reaction efficiently accelerated by Schreiner's thiourea is reported, to build a functionalized cytochalasin scaffold (periconiasin series) for biological purposes. DFT calculation highlighted a unique multidentate cooperative hydrogen bonding in this catalysis. The deprotection end game afforded a collection of diverse structures and showed the peculiar reactivity of the
The totalsynthesis of the smallest cytochalasin isolated so far, periconiasin G, which bears a seven‐membered ring in lieu of the usual macrocycle, has been performed from both enantiomers of citronellal, relying on an intramolecular Diels–Alder reaction in favor of the natural endo stereochemistry. We show that, among the four synthesized stereoisomers, including the exo isomers, the one matching
The first and collective totalsyntheses of periconiasins A–E, a group of naturally occurring cytochalasans, were achieved by a series of rationally designed or bioinspired transformations. Salient features of the syntheses include a tandem aldol condensation/Grob fragmentation to assemble the linear polyketide–amino acid hybrid precursor, a Diels–Alder macrocylization to construct the 9/6/5 tricyclic
The first total syntheses of the cytochalasan dimers asperchalasines A, D, E, and H have been accomplished. The key steps of the synthesis include a highly stereoselective intermolecular Diels–Alder reaction and a Horner–Wadsworth–Emmons macrocyclization to establish the key monomer aspochalasin B, and an intermolecular Diels–Alder reaction followed by a biomimetic oxidative heterodimerization by 5+2