Tremorgenic indole alkaloids. The total synthesis of (-)-penitrem D

A convergent, stereocontrolled total synthesis of the architecturally complex tremorgenic indole alkaloid (-)-penitrem D (4) has been achieved. Highlights of the synthesis include an efficient, asymmetric synthesis of the western hemisphere; the stereocontrolled assembly of the I-ring; discovery of a novel autoxidation to introduce the C(22) tertiary hydroxyl group, required for tremorgenic activity; union of fully elaborated eastern and western hemispheres, exploiting an indole synthetic protocol developed expressly for this purpose; and a late-stage, stereoselective construction of the A and F rings exploiting a Sc(OTf)(3-)promoted reaction cascade. The longest linear sequence leading to (-)-penitrem D (4) was 43 steps.     

Construction of macrocyclic thiodepsipeptides: synthesis of a nosiheptide 'southern hemisphere' model system

A 20-membered macrocyclic thiodepsipeptide has been synthesized as a model for the southern hemisphere of nosiheptide, the key steps being assembly of an acyclic precursor by amide coupling of indole and thiazole fragments followed by formation of the thiolactone in the macrocyclization step.     

吲哚类生物碱的合成研究进展

吲哚类生物碱是具有吲哚分子骨架的一类化合物,具有多种良好的生理活性。文章综述了近年来新发现吲哚类生物碱的合成研究进展,介绍了(-)-Arboricine,(±)-cis-Trikentrin A,(-)-Corynantheidol等化合物的合成方法。     

Catalytic Functionalization of Indoles in a New Dimension

140 Years ago Adolf von Baeyer proposed the structure of a heteroaromatic compound which revolutionized organic and medical chemistry: indole. After more than a century, indole itself and the complexity of naturally occurring indole derivatives continue to inspire and influence developments in synthetic chemistry. In particular, the ubiquitous presence of indole rings in pharmaceuticals, agrochemicals, and functional materials are testament to the ever increasing interest in the design of mild and efficient synthetic routes to functionalized indole derivatives. This Review emphasizes the achievements in the selective catalytic functionalization of indoles (C? C bond‐forming processes) over the last four years.     

An efficient synthesis of Ecopladib

An efficient synthesis of Ecopladib, an indole inhibitor of cytosolic phospholipase A₂α, is described. A new reaction involving indole C3 reductive alkylation using an acetal in the absence of water and a novel transformation of the C2 methyl to an aldehyde via dimethyl sulfoxide-mediated oxygen-transfer reaction are used in the present synthesis, which dramatically increased the synthetic efficiency.     

New syntheses of cycloalka[<Emphasis Type="Italic">b</Emphasis>]indoles

The review summarizes most recent synthetic approaches to compounds containing a cycloalka[b]- indole fragment as the main structural unit. Improved procedures for the preparation of cycloalka[b]indole heterocycles have been described, and their applications in the synthesis of natural and synthetic biologically active congeners have been considered.     

Indole-Based Tubulin Inhibitors: Binding Modes and SARs Investigations

Tubulin inhibitors can interfere with normal cell mitosis and inhibit cell proliferation through interfering with the normal structure and function of microtubules, forming spindle filaments. Indole, as a privileged pharmacological skeleton, has been widely used in anti-cancer inhibitors. A variety of alkaloids containing an indole core obtained from natural sources have been proven to inhibit tubulin polymerization, and an ever-increasing number of synthetic indole-based tubulin inhibitors have been reported. Among these, several kinds of indole-based derivatives, such as TMP analogues, aroylindoles, arylthioindoles, fused indole, carbazoles, azacarbolines, alkaloid nortopsentin analogues and bis-indole derivatives, have shown good inhibition activities towards tubulin polymerization. The binding modes and SARs investigations of synthetic indole derivatives, along with a brief mechanism on their anti-tubulin activity, are presented in this review.     

单萜吲哚生物碱Uleine及其衍生物的合成进展

生物碱uleine及其衍生物从结构上看属于单萜吲哚生物碱,它们共同的结构特征是吲哚核与碱性氮原子之间只有一个碳相隔,而不像其它单萜吲哚生物碱有两个碳原子.由于其结构特异,天然含量少,因而其合成工作一直吸引着化学工作者.总结uleine生物碱及其衍生物的合成方法,根据构建环的种类不同,把合成方法分为五类.大部分方法都是以吲哚和吡啶衍生物为起始原料进行四环的合成,有几条合成路线简短易行.     

褪黑激素的合成——介绍一个探索性有机化学实验

介绍一个面向大学二年级本科生的探索性实验。基于专利文献方法的合成路线较为适宜学生实验且具有良好训练价值:以邻苯二甲酰亚胺、1,3-二溴丙烷、乙酰乙酸乙酯、对甲氧基苯胺为基本原料,以Japp-Klingemann反应和Fischer吲哚合成法联用构建吲哚环,经水解脱羧、乙酰化,合成了褪黑激素。对学生在实验中的条件优化探索进行了简要介绍。     

Search for Non-Protein Protease Inhibitors Constituted with an Indole and Acetylene Core

A possible inhibitor of proteases, which contains an indole core and an aromatic polar acetylene, was designed and synthesized. This indole derivative has a molecular architecture kindred to biologically relevant species and was obtained through five synthetic steps with an overall yield of 37% from the 2,2′-(phenylazanediyl)di(ethan-1-ol). The indole derivative was evaluated through docking assays using the main protease (SARS-CoV-2-M^pro) as a molecular target, which plays a key role in the replication process of this virus. Additionally, the indole derivative was evaluated as an inhibitor of the enzyme kallikrein 5 (KLK5), which is a serine protease that can be considered as an anticancer drug target.     

An efficient approach to Aspidosperma alkaloids via [4 + 2] cycloadditions of aminosiloxydienes: stereocontrolled total synthesis of (+/-)-tabersonine. Gram-scale catalytic asymmetric syntheses of (+)-tabersonine and (+)-16-methoxytabersonine. Asymmetric syntheses of (+)-aspidospermidine and (-)-quebrachamine

Described is a concise, highly stereocontrolled strategy to the Aspidosperma family of indole alkaloids, one that is readily adapted to the asymmetric synthesis of these compounds. The strategy is demonstrated by the total synthesis of (+/-)-tabersonine (rac-1), proceeding through a 12-step sequence. The basis for this approach was provided by a highly regio- and stereoselective [4 + 2] cycloaddition of 2-ethylacrolein with 1-amino-3-siloxydiene developed in our laboratory. Subsequent elaboration of the initial adduct into the hexahydroquinoline DE ring system was accomplished efficiently by a ring-closing olefin metathesis reaction. A novel ortho nitrophenylation of an enol silyl ether with (o-nitrophenyl)phenyliodonium fluoride was developed to achieve an efficient, regioselective introduction of the requisite indole moiety. The final high-yielding conversion of the ABDE tetracycle into pentacyclic target rac-1 relied on intramolecular indole alkylation and regioselective C-carbomethoxylation. Our approach differs strategically from previous routes and contains built-in flexibility necessary to access many other members of the Aspidosperma family of indole alkaloids. The versatility of the synthetic strategy was illustrated through the asymmetric syntheses of the following Aspidosperma alkaloids: (+)-aspidospermidine, (-)-quebrachamine, (-)-dehydroquebrachamine, (+)-tabersonine, and (+)-16-methoxytabersonine. Of these, (+)-tabersonine and (+)-16-methoxytabersonine were synthesized in greater than 1-g quantities and in enantiomerically enriched form ( approximately 95% ee). The pivotal asymmetry-introducing step was a catalyzed enantioselective Diels-Alder reaction, which proceeded to afford the cycloadducts in up to 95% ee. Significantly, the synthetic sequence was easy to execute and required only four purifications over the 12-step synthetic route.     

Fluorapatite: An Effective Solid Base Catalyst for Michael Addition of Indole/pyrrole to Nitroalkenes under Solventless Condition

Solid base fluorapatite was found to catalyze the Michael addition of indole/pyrrole to nitroalkenes efficiently under solventless condition, affording the products in good to excellent yields. The Michael addition occurred at the 3‐position of indole exclusively with an exception of 3‐methylindole. The synthetic fluorapatite could be recovered and reused easily without obvious loss in activity.     

Synthesis of indole-5,6- and carbazole-2,3-dicarboxylic acid functional derivatives

Principal synthetic approaches to the synthesis of indole-5,6- and carbazole-2,3-dicarboxylic acid functional derivatives are considered. The first of them consists in the construction of the indole ring from simpler aromatic compounds containing carboxy groups, cyano groups, or an imide fragment with subsequent reductive cyclization of the compounds formed. The second approach is based on the modification of a pyrrole or an indole fragment by the introduction of different functional groups with subsequent intramolecular cyclization to the corresponding heterocycles.     

Recent Advances on Direct Functionalization of Indoles in Aqueous Media

Indoles and their derivatives have dominated a significant proportion of nitrogen-containing heterocyclic compounds and play an essential role in synthetic and medicinal chemistry, pesticides, and advanced materials. Compared with conventional synthetic strategies, direct functionalization of indoles provides straightforward access to construct diverse indole scaffolds. As we enter an era emphasizing green and sustainable chemistry, utilizing environment-friendly solvents represented by water demonstrates great potential in synthesizing valuable indole derivatives. This review aims to depict the critical aspects of aqueous-mediated indoles functionalization over the past decade and discusses the future challenges and prospects in this fast-growing field. For the convenience of readers, this review is classified into three parts according to the bonding modes (C−C, C−N, and C−S bonds), which focus on the diversity of indole derivatives, the prominent role of water in the chemical process, and the types of catalyst systems and mechanisms. We hope this review can promote the sustainable development of the direct functionalization of indoles and their derivatives and the discovery of novel and practical organic methods in aqueous phase.     

Modular synthesis of candidate indole-based insulin mimics by Claisen rearrangement

A modular synthetic route to (indolyl)kojic acid anti-diabetes agents has been developed. Sonogashira coupling of a protected iodoaniline with a propargyl kojate was used to construct an (indole)methyl kojate. Its heteroaromatic Claisen rearrangement, followed by tautomerization to return the indole and pyrone rings, was used to create the biaryl C-C bond. This route should enable collections of insulin mimic drug candidates to be prepared from a few basic building blocks.     

Synthesis of N-substituted indole derivatives via PIFA-mediated intramolecular cyclization

[Structure: see text] A variety of N-arylated and N-alkylated indole derivatives were synthesized by way of a phenyliodine bis(trifluoroacetate) (PIFA)-mediated intramolecular cyclization. This novel method allows for the construction of an indole skeleton by joining the N-atom on the side chain to the benzene ring at the last synthetic step. Other novel pyrrole-fused aromatic compounds can also be achieved by this method.     

Indole‐Diterpene Synthetic Studies: Total Synthesis of (−)‐21‐Isopentenylpaxilline

An efficient, stereocontrolled total synthesis of the complex indole‐diterpene alkaloid (?)‐21‐isopentenylpaxilline ( 1 ) has been achieved. Key elements of the synthesis include the stereocontrolled construction of the advanced eastern hemisphere (?)‐ 68 , involving a highly efficient union of the eastern and western fragments (?)‐ 68 and 5 exploiting our 2‐substituted indole synthesis, application of the Negishi π cycloalkylation tactic as a new, potentially general protocol for the construction of ring C, and the fragmentation of a β,γ‐epoxy ketone to introduce the tertiary OH group at C(13) in the indole diterpene skeleton.     

Asymmetric Friedel-crafts reaction of indoles with imines by an organic catalyst

In this communication, we report an asymmetric Friedel-Crafts reaction of indoles with imines catalyzed by a bifunctional cinchona alkaloid catalyst. This is the first efficient organocatalytic asymmetric Friedel-Crafts reaction of indoles with imines. This reaction is operationally simple and, unprecedentedly, affords high enantioselectivity for a wide range of indoles and both aryl and alkyl imines. This establishes a direct, convergent, and versatile approach to optically active 3-indolyl methanamines, a structural motif embedded in numerous indole alkaloids and synthetic indole derivatives.     

Synthesis of the new ring system 2-oxo-[1,4]oxazino[3,2-e]indole, heteroanalogue of Angelicin

A convenient synthesis of the 2-oxo-[1,4]oxazino[3,2-e]indole ring system, an heteroanalogue of Angelicin, is reported. Our synthetic approach consisted of the annelation of the oxazine ring on the indole moiety using 4-amino-5-hydroxy indoles as building blocks. The antiproliferative activity of the new compounds either in the dark or under UVA irradiation was investigated.     

Indole‐N‐Carboxylic Acids and Indole‐N‐Carboxamides in Organic Synthesis

Indoles are ubiquitous structures that are found in natural products and biologically active molecules. The synthesis of indoles and indole‐involved synthetic methodologies in organic chemistry have been receiving considerable attention. Indole‐N‐carboxylic acids and derived indole‐N‐carboxamides are intriguing compounds, which have been widely used in organic synthesis, especially in multicomponent reactions and C?H functionalization of indoles. This Minireview summarizes the advances of reactions involving indole‐N‐carboxylic acids and indole‐N‐carboxamides in organic chemistry, and discusses the synthetic potential and perspective of this field.