1
|
Metal-free sp 2 -C7-H Borylation of Tryptophan Containing Peptides and Late-stage Modification. Chem Asian J 2023; 18:e202300638. [PMID: 37847482 DOI: 10.1002/asia.202300638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/06/2023] [Accepted: 10/16/2023] [Indexed: 10/18/2023]
Abstract
The discovery of milder and robust strategies to enable the introduction of organoboronates in peptides remains conspicuously underdeveloped. Herein, we demonstrate an efficient method for the site-selective sp2 -C7-H borylation of tryptophan under metal-free condition using BBr3 directed by pivaloyl group. The versatility of this approach is that gram scale synthesis and C7-borylated N-Phth-Trp(N-Piv)(C7-BPin)-OMe was modified into various C7-substituted derivatives. Moreover, the strategy enables for the peptide elongation and late-stage borylation of peptides, natural product Brevianamide F and drug Oglufanide.
Collapse
|
2
|
Transition-metal catalyzed C-H activation as a means of synthesizing complex natural products. Chem Soc Rev 2023; 52:7461-7503. [PMID: 37811747 DOI: 10.1039/d3cs00282a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Over the past few decades, the advent of C-H activation has led to a rethink among chemists about the synthetic strategies employed for multi-step transformations. Indeed, deploying innovative and masterful tricks against the numerous classical organic transformations has been the need of the hour. Despite this, the immense importance of C-H activation remains unfulfilled unless the methodology can be deployed for large-scale industrial processes and towards the concise, step-economic synthesis of prodigious natural products and pharmaceutical drugs. Lately, the growing potential of C-H activation methodology has indeed driven the pioneers of synthetic organic chemists into finding more efficient methods to accelerate the synthesis of such complex molecular scaffolds. This review aims to draw a general overview of the various C-H activation procedures that have been adopted for synthesizing these vast majority of structurally complicated natural products. Our objective lies in drawing a complete picture and taking the readers through the synthesis of a series of such complex organic compounds by simplified techniques, making it step-economic on a larger scale and thus instigating the readers to trigger the use of such methodology and uncover new, unique patterns for future synthesis of such natural products.
Collapse
|
3
|
Preparation of NIn-Methyl-6-[ 18F]fluoro- and 5-Hydroxy-7-[ 18F]fluorotryptophans as Candidate PET-Tracers for Pathway-Specific Visualization of Tryptophan Metabolism. Int J Mol Sci 2023; 24:15251. [PMID: 37894930 PMCID: PMC10607147 DOI: 10.3390/ijms242015251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/09/2023] [Accepted: 10/14/2023] [Indexed: 10/29/2023] Open
Abstract
Tryptophan (Trp) is an essential proteinogenic amino acid and metabolic precursor for several signaling molecules that has been implicated in many physiological and pathological processes. Since the two main branches of Trp metabolism-serotonin biosynthesis and kynurenine pathway-are differently affected by a variety of neurological and neoplastic diseases, selective visualization of these pathways is of high clinical relevance. However, while positron emission tomography (PET) with existing probes can be used for non-invasive assessment of total Trp metabolism, optimal imaging agents for pathway-specific PET imaging are still lacking. In this work, we describe the preparation of two 18F-labeled Trp derivatives, NIn-methyl-6-[18F]fluorotryptophan (NIn-Me-6-[18F]FTrp) and 5-hydroxy-7-[18F]fluorotryptophan (5-HO-7-[18F]FTrp). We also report feasible synthetic routes for the preparation of the hitherto unknown boronate radiolabeling precursors and non-radioactive reference compounds. Under optimized conditions, alcohol-enhanced Cu-mediated radiofluorination of the respective precursors afforded NIn-Me-6-[18F]FTrp and 5-HO-7-[18F]FTrp as application-ready solutions in radiochemical yields of 45 ± 7% and 29 ± 4%, respectively. As such, our work provides access to two promising candidate probes for pathway-specific visualization of Trp metabolism in amounts sufficient for their preclinical evaluation.
Collapse
|
4
|
Transition-Metal-Catalyzed Silylation and Borylation of C-H Bonds for the Synthesis and Functionalization of Complex Molecules. Chem Rev 2023; 123:11619-11663. [PMID: 37751601 DOI: 10.1021/acs.chemrev.3c00207] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/28/2023]
Abstract
The functionalization of C-H bonds in organic molecules containing functional groups has been one of the holy grails of catalysis. One synthetically important approach to the diverse functionalization of C-H bonds is the catalytic silylation or borylation of C-H bonds, which enables a broad array of downstream transformations to afford diverse structures. Advances in both undirected and directed methods for the transition-metal-catalyzed silylation and borylation of C-H bonds have led to their rapid adoption in early-, mid-, and late-stage of the synthesis of complex molecules. In this Review, we review the application of the transition-metal-catalyzed silylation and borylation of C-H bonds to the synthesis of bioactive molecules, organic materials, and ligands. Overall, we aim to provide a picture of the state of art of the silylation and borylation of C-H bonds as applied to the synthesis and modification of diverse architectures that will spur further application and development of these reactions.
Collapse
|
5
|
Divergent total syntheses of ITHQ-type bis-β-carboline alkaloids by regio-selective formal aza-[4 + 2] cycloaddition and late-stage C-H functionalization. Chem Sci 2023; 14:10353-10359. [PMID: 37772099 PMCID: PMC10530148 DOI: 10.1039/d3sc03722c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/04/2023] [Indexed: 09/30/2023] Open
Abstract
We herein report the first total syntheses of several bis-β-carboline alkaloids, picrasidines G, S, R, and T, and natural product-like derivatives in a divergent manner. Picrasidines G, S, and T feature an indolotetrahydroquinolizinium (ITHQ) skeleton, while picrasidine R possesses a 1,4-diketone linker between two β-carboline fragments. The synthesis of ITHQ-type bis-β-carboline alkaloids could be directly achieved by a late-stage regio-selective aza-[4 + 2] cycloaddition of vinyl β-carboline alkaloids, suggesting that this remarkable aza-[4 + 2] cycloaddition might be involved in the biosynthetic pathway. Computational studies revealed that such aza-[4 + 2] cycloaddition is a stepwise process and explained the unique regioselectivity (ΔΔG = 3.77 kcal mol-1). Moreover, the successful application of iridium-catalyzed C-H borylation on β-carboline substrates enabled the site-selective C-8 functionalization for efficient synthesis and structural diversification of this family of natural products. Finally, concise synthesis of picrasidine R by the thiazolium-catalyzed Stetter reaction was also accomplished.
Collapse
|
6
|
B(C 6F 5) 3-mediated direct intramolecular C7-alkenylation of N-propargylindoles. Chem Commun (Camb) 2023; 59:10279-10282. [PMID: 37539546 DOI: 10.1039/d3cc02599c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
B(C6F5)3-mediated direct C7-alkenylation of N-propargylindoles without directing groups was developed. This reaction proceeds via the π-activation of the alkynyl group with B(C6F5)3/Friedel-Crafts alkenylation/proton transfer reaction sequence. Interestingly, C7-alkenylation products could further convert into the fused indoles by deprotonation and finally polyaromatic N-heterocycles by the hydride abstraction.
Collapse
|
7
|
Total synthesis of complex 2,5-diketopiperazine alkaloids. THE ALKALOIDS. CHEMISTRY AND BIOLOGY 2023; 90:159-206. [PMID: 37716796 PMCID: PMC10955524 DOI: 10.1016/bs.alkal.2023.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/18/2023]
Abstract
The 2,5-diketopiperazine (DKP) motif is present in many biologically relevant, complex natural products. The cyclodipeptide substructure offers structural rigidity and stability to proteolysis that makes these compounds promising candidates for medical applications. Due to their fascinating molecular architecture, synthetic organic chemists have focused significant effort on the total synthesis of these compounds. This review covers many such efforts on the total synthesis of DKP containing complex alkaloid natural products.
Collapse
|
8
|
Selective Labeling of Peptides with o-Carboranes via Manganese(I)-Catalyzed C-H Activation. Chemistry 2022; 28:e202200811. [PMID: 35420234 PMCID: PMC9320968 DOI: 10.1002/chem.202200811] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Indexed: 12/15/2022]
Abstract
A robust method for the selective labeling of peptides via manganese(I) catalysis was devised to achieve the C-2 alkenylation of tryptophan containing peptides with 1-ethynyl-o-carboranes. The manganese-catalyzed C-H activation was accomplished with high catalytic efficiency, and featured low toxicity, high functional group tolerance and excellent E-stereoselectivity. This approach unravels a promising tool for the assembly of o-carborane with structurally complex peptides of relevance to applications in boron neutron capture therapy.
Collapse
|
9
|
Indolactam Dipeptides as Nanomolar Gli Inhibitors. ACS Med Chem Lett 2022; 13:1036-1042. [DOI: 10.1021/acsmedchemlett.1c00562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
|
10
|
Abstract
We report the first total synthesis of (-)-kopsifoline A and (+)-kopsifoline E. Our synthetic strategy features a biogenetically inspired regioselective C17-functionalization of a versatile intermediate containing the pentacyclic core of aspidosperma alkaloids. The vinylogous urethane substructure of this intermediate affords (-)-kopsifoline D via C3-C21 bond formation under the Mitsunobu reaction conditions, while it enables selective C17-functionalization en route to (-)-kopsifoline A and (+)-kopsifoline E.
Collapse
|
11
|
Aspidosperma and Strychnos alkaloids: Chemistry and biology. THE ALKALOIDS. CHEMISTRY AND BIOLOGY 2021; 86:1-143. [PMID: 34565505 DOI: 10.1016/bs.alkal.2021.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
Abstract
Of Nature's nearly 3000 unique monoterpene indole alkaloids derived from tryptophan, those members belonging to the Aspidosperma and Strychnos families continue to impact the fields of natural products (i.e., isolation, structure determination, biosynthesis) and organic chemistry (i.e., chemical synthesis, methodology development) among others. This review covers the biological activity (Section 2), biosynthesis (Section 3), and synthesis of both classical and novel Aspidosperma (Section 4), Strychnos (Section 5), and selected bis-indole (Section 6) alkaloids. Technological advancements in genetic sequencing and bioinformatics have deepened our understanding of how Nature assembles these intriguing molecules. The proliferation of innovative synthetic strategies and tactics for the synthesis of the alkaloids covered in this review, which include contributions from over fifty research groups from around the world, are a testament to the creative power and technical skills of synthetic organic chemists. To be sure, Nature-the Supreme molecular architect and source of a dazzling array of irresistible chemical logic puzzles-continues to inspire scientists across multiple disciplines and will certainly continue to do so for the foreseeable future.
Collapse
|
12
|
Double Arylation of the Indole Side Chain of Tri- and Tetrapodal Tryptophan Derivatives Renders Highly Potent HIV-1 and EV-A71 Entry Inhibitors†. J Med Chem 2021; 64:10027-10046. [PMID: 34229438 PMCID: PMC8389807 DOI: 10.1021/acs.jmedchem.1c00315] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
![]()
We have recently
described a new generation of potent human immunodeficiency
virus (HIV) and EV-A71 entry inhibitors. The prototypes contain three
or four tryptophan (Trp) residues bearing an isophthalic acid moiety
at the C2 position of each side-chain indole ring. This work is now
extended by both shifting the position of the isophthalic acid to
C7 and synthesizing doubly arylated C2/C7 derivatives. The most potent
derivative (50% effective concentration (EC50) HIV-1, 6
nM; EC50 EV-A71, 40 nM), 33 (AL-518), is a C2/C7 doubly arylated tetrapodal compound. Its superior anti-HIV
potency with respect to the previous C2-arylated prototype is in consonance
with its higher affinity for the viral gp120. 33 (AL-518) showed comparable antiviral activities against X4
and R5 HIV-1 strains and seems to interact with the tip and base of
the gp120 V3 loop. Taken together, these findings support the interest
in 33 (AL-518) as a useful new prototype
for anti-HIV/EV71 drug development.
Collapse
|
13
|
Palladium-Catalyzed Remote C-H Phosphonylation of Indoles at the C4 and C6 Positions by a Radical Approach. Angew Chem Int Ed Engl 2021; 60:13871-13876. [PMID: 33851763 DOI: 10.1002/anie.202103395] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Indexed: 11/09/2022]
Abstract
Palladium-catalyzed direct C-H activation of indole benzenoid moiety has been achieved in the past decade. However, palladium-catalyzed remote C-H activation of indoles is rare. Herein, we report a challenging palladium-catalyzed remote C4-H phosphonylation of indoles by a radical approach. The method provides access to a series of C4-phosphonylated indoles, including tryptophan and tryptophan-containing dipeptides, which are typically inaccessible by direct C4-H activation due to its heavy reliance on C3 directing groups. Notably, unexpected C6-phosphonylated indoles were obtained through blocking of the C4 position. The preliminary mechanistic studies indicated that the reactions may proceed via a C7-palladacycle/remote-activation process. Based on the strategy, examples of remote C4-H difluoromethylation with BrCF2 COOEt are also presented, suggesting that the strategy may offer a general blueprint for other cross-couplings.
Collapse
|
14
|
Palladium‐Catalyzed Remote C−H Phosphonylation of Indoles at the C4 and C6 Positions by a Radical Approach. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202103395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
15
|
Abstract
This review summarises a wide range of transformations on the indole skeleton, including arylation, alkenylation, alkynylation, acylation, nitration, borylation, and amidation, using transition-metal catalyzed C–H functionalization as the key step.
Collapse
|
16
|
Staurosporine Analogs Via C-H Borylation. ACS Med Chem Lett 2020; 11:2441-2445. [PMID: 33335665 DOI: 10.1021/acsmedchemlett.0c00420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 10/06/2020] [Indexed: 12/17/2022] Open
Abstract
Staurosporine is among the most potent naturally occurring kinase inhibitors isolated to date and has served as a lead compound for numerous drug development efforts in several therapeutic areas. Herein we report that C-H borylation chemistry provides access to analogs of staurosporine that were previously inaccessible to medicinal chemists who, in the past four decades, have prepared over 1000 semisynthetic staurosporine analogs.
Collapse
|
17
|
|
18
|
11C- and 18F-labelled tryptophans as PET-tracers for imaging of altered tryptophan metabolism in age-associated disorders. RUSSIAN CHEMICAL REVIEWS 2020. [DOI: 10.1070/rcr4954] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The ageing of the world’s population is the result of increased life expectancy observed in almost all countries throughout the world. Consequently, a rising tide of ageing-associated disorders, like cancer and neurodegenerative diseases, represents one of the main global challenges of the 21st century. The ability of mankind to overcome these challenges is directly dependent on the capability to develop novel methods for therapy and diagnosis of age-associated diseases. One hallmark of age-related pathologies is an altered tryptophan metabolism. Numerous pathological processes including neurodegenerative and neurological diseases like epilepsy, Parkinson’s and Alzheimer’s diseases, cancer and diabetes exhibit marked changes in tryptophan metabolism. Visualization of key processes of tryptophan metabolic pathways, especially using positron emission tomography (PET) and related hybrid methods like PET/CT and PET/MRI, can be exploited to early detect the aforementioned disorders with considerable accuracy, allowing appropriate and timely treatment of patients. Here we review the published 11C- and 18F-labelled tryptophans with respect to the production and also preclinical and clinical evaluation as PET-tracers for visualization of different branches of tryptophan metabolism.
The bibliography includes 159 references.
Collapse
|
19
|
Boron Accumulation in Brain Tumor Cells through Boc-Protected Tryptophan as a Carrier for Boron Neutron Capture Therapy. ACS Med Chem Lett 2020; 11:589-596. [PMID: 32292568 DOI: 10.1021/acsmedchemlett.0c00064] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 03/16/2020] [Indexed: 12/16/2022] Open
Abstract
Boron neutron capture therapy (BNCT) is a binary therapeutic approach. Nonradioactive boron-10 atoms accumulated in tumor cells combining with the neutron beams produce two highly energetic particles that could eradicate the cell that takes it and the neighboring cells. Small molecules that carry boron atom, e.g. 5- and 6-boronated and 2,7-diboronated tryptophans, were assessed for their boron accumulation in U87-MG, LN229, and 3T3 for BNCT. TriBoc tryptophan, TB-6-BT, shows boron-10 at 300 ppm in both types of tumor cells with a tumor to normal ratio (T/N) of 5.19-5.25 (4 h). TB-5-BT and DBA-5-BT show boron-10 at 300 ppm (2 h) in U87-MG cells. TB-5-BT exerts a T/N of >9.66 (1 h) in LN229 compared with the current clinical boronophenyl alanine with a highest T/N of 2.3 (1 h) and accumulation concentration of <50 ppm. TB-5-BT and TB-6-BT warrant further animal study.
Collapse
|
20
|
One-pot oxidative hydrolysis-oxidative cleavage of 7-borylindoles enables access to o-amidophenols and 4-acylbenzoxazoles. Chem Commun (Camb) 2020; 56:3559-3562. [PMID: 32104796 DOI: 10.1039/c9cc09807k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
7-Borylindoles undergo a one-pot oxidative-hydrolysis of the arylboronate and oxidative cleavage of the indole C2-C3 double bond to afford o-amidophenol derivatives. Subsequent cyclisation delivers benzoxazoles bearing an acyl group at C4, a substitution pattern common to fungal-derived benzoxazole alkaloids. Using 7-borylindoles as substrates to access functionalised o-amidophenols circumvents the difficult preparation of these compounds from arenes, streamlining access to substituted 4-acylbenzoxazoles in the process.
Collapse
|
21
|
|
22
|
Iridium-Catalyzed Dehydrogenative Reactions. TOP ORGANOMETAL CHEM 2020. [DOI: 10.1007/3418_2020_56] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
23
|
Acyl-Directed ortho-Borylation of Anilines and C7 Borylation of Indoles using just BBr 3. Angew Chem Int Ed Engl 2019; 58:15381-15385. [PMID: 31461213 PMCID: PMC6856876 DOI: 10.1002/anie.201909786] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Indexed: 01/04/2023]
Abstract
Indoles are privileged heterocycles found in many biologically active pharmaceuticals and natural products. However, the selective functionalization of the benzenoid moiety in indoles in preference to the more reactive pyrrolic unit is a significant challenge. Herein we report that N-acyl directing groups enable the C7-selective C-H borylation of indoles using just BBr3 . This transformation shows some functional-group tolerance and notably proceeds with C6 substituted indoles. The directing group can be readily removed in situ and the products isolated as the pinacol boronate esters. Acyl-directed electrophilic borylation can be extended to carbazoles and anilines with excellent ortho selectivity. 4-amino-indoles are amenable to this process, with acyl group installation and directed electrophilic C-H borylation enabling selective formation of C5-BPin-indoles.
Collapse
|
24
|
Abstract
Indole derivatives are associated with a variety of both biological activities and applications in the field of material chemistry. A number of different strategies for synthesizing substituted indoles by means of the reactions of indolylboronic acids with electrophilic compounds are considered the methods of choice for modifying indoles because indolylboronic acids are easily available, stable, non-toxic and new reactions using indolylboronic acids have been described in the literature. Thus, the aim of this review is to summarize the methods available for the preparation of indolylboronic acids as well as their chemical transformations. The review covers the period 2010-2019.
Collapse
|
25
|
Acyl‐Directed
ortho
‐Borylation of Anilines and C7 Borylation of Indoles using just BBr
3. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201909786] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
|
26
|
Development of indazole mineralocorticoid receptor antagonists and investigation into their selective late-stage functionalization. Bioorg Med Chem Lett 2019; 29:1854-1858. [DOI: 10.1016/j.bmcl.2019.04.024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 04/11/2019] [Accepted: 04/13/2019] [Indexed: 11/24/2022]
|
27
|
C7‐Functionalization of Indoles via Organocatalytic Enantioselective Friedel‐Crafts Alkylation of 4‐Amino‐ indoles with 2‐Butene‐1,4‐diones and 3‐Aroylacrylates. Adv Synth Catal 2019. [DOI: 10.1002/adsc.201900377] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
28
|
A Convenient C-H Functionalization Platform for Pyrroloiminoquinone Alkaloid Synthesis. Tetrahedron 2019; 75:3366-3370. [PMID: 31889735 DOI: 10.1016/j.tet.2019.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Pyrroloiminoquinone alkaloids represent a structurally intriguing class of natural products that display an array of useful biological properties. Here, we present a versatile and scalable platform for the synthesis of this diverse family - and in particular the antitumor discorhabdins - built upon sequential selective C-H functionalization of tryptamine. The utility of this strategy is showcased through short formal syntheses of damirones A-C, makaluvamines D and I, and discorhadbin E. Additionally, we describe efforts to develop the first catalytic asymmetric entry to the discorhabdin subclass.
Collapse
|
29
|
1,2-Azaborine's Distinct Electronic Structure Unlocks Two New Regioisomeric Building Blocks via Resolution Chemistry. J Am Chem Soc 2019; 141:9072-9078. [PMID: 31082254 PMCID: PMC6609151 DOI: 10.1021/jacs.9b03611] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Two new 1,2-azaborine building blocks that enable the broad diversification of previously not readily accessible C4 and C5 ring positions of the 1,2-azaborine heterocycle are developed. 1,2-Azaborine's distinct electronic structure allowed the resolution of a mixture of C4- and C5-borylated 1,2-azaborines. The connection between the electronic structure of C4 and C5 positions of 1,2-azaborine and their distinct reactivity patterns is revealed by a combination of reactivity studies and kinetic measurements that are supported by DFT calculations. Specifically, we show that oxidation by N-methylmorpholine N-oxide (NMO) is selective for the C4-borylated 1,2-azaborine, and the Ir-catalyzed deborylation is selective for the C5-borylated 1,2-azaborine via kinetically controlled processes. On the other hand, ligand exchange with diethanolamine takes place selectively with the C4-borylated isomer via a thermodynamically controlled process. These results represent the first examples for chemically distinguishing a mixture of two aryl mono-Bpin-substituted isomers.
Collapse
|
30
|
Directing-Group-Free C7-Alkylations of N-Alkylindoles Mediated by Cationic Zirconium Complexes: Role of Brønsted Acid for Catalytic Manifold. Chemistry 2019; 25:7292-7297. [PMID: 30893504 DOI: 10.1002/chem.201901268] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Indexed: 01/05/2023]
Abstract
Highly position selective alkylations of N-alkylindoles at C7-positions have been enabled by cationic zirconium complexes. The strategy provides a straightforward access to install alkyl groups at C7-positions of indoles without a complex directing group. Mechanistic studies provided support for the importance of Brønsted acids in the catalytic manifold.
Collapse
|
31
|
Rhodium-Catalyzed Selective C–H Trideuteromethylation of Indole at C7 Position Using Acetic-d6 Anhydride. J Org Chem 2019; 84:12764-12772. [DOI: 10.1021/acs.joc.9b01114] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
32
|
Rhodium‐Catalyzed C−H Functionalization of
N
‐(2‐Pyrimidyl)indole with Internal Alkynes: Formation of Unexpected Products by Regulating the Amount of Silver Acetate. Adv Synth Catal 2019. [DOI: 10.1002/adsc.201900105] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
|
33
|
Transition-metal-catalyzed site-selective C7-functionalization of indoles: advancement and future prospects. Chem Commun (Camb) 2019; 55:572-587. [DOI: 10.1039/c8cc04116d] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The advancement and future prospects of transition-metal-catalyzed auxiliary assisted regioselective C7-functionalization of indoles/indolines are covered in this article.
Collapse
|
34
|
Divergent Total Syntheses of C3 a−C7′ Linked Diketopiperazine Alkaloids (+)-Asperazine and (+)-Pestalazine A Enabled by a Ni-Catalyzed Reductive Coupling of Tertiary Alkyl Chloride. Chemistry 2018; 25:989-992. [DOI: 10.1002/chem.201805682] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Indexed: 12/17/2022]
|
35
|
|
36
|
Development of Mithramycin Analogues with Increased Selectivity toward ETS Transcription Factor Expressing Cancers. J Med Chem 2018; 61:8001-8016. [PMID: 30114371 DOI: 10.1021/acs.jmedchem.8b01107] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mithramycin A (1) was identified as the top potential inhibitor of the aberrant ETS transcription factor EWS-FLI1, which causes Ewing sarcoma. Unfortunately, 1 has a narrow therapeutic window, compelling us to seek less toxic and more selective analogues. Here, we used MTMSA (2) to generate analogues via peptide coupling and fragment-based drug development strategies. Cytotoxicity assays in ETS and non-ETS dependent cell lines identified two dipeptide analogues, 60 and 61, with 19.1- and 15.6-fold selectivity, respectively, compared to 1.5-fold for 1. Importantly, the cytotoxicity of 60 and 61 is <100 nM in ETS cells. Molecular assays demonstrated the inhibitory capacity of these analogues against EWS-FLI1 mediated transcription in Ewing sarcoma. Structural analysis shows that positioning the tryptophan residue in a distal position improves selectivity, presumably via interaction with the ETS transcription factor. Thus, these analogues may present new ways to target transcription factors for clinical use.
Collapse
|
37
|
A Bioinspired Synthesis of Polyfunctional Indoles. Angew Chem Int Ed Engl 2018; 57:11963-11967. [PMID: 29978600 DOI: 10.1002/anie.201806490] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 06/29/2018] [Indexed: 01/25/2023]
|
38
|
|
39
|
Abstract
The first enantioselective total synthesis of (-)-vallesine via a strategy that features a late-stage regioselective C17-oxidation followed by a highly stereoselective transannular cyclization is reported. The versatility of this approach is highlighted by the divergent synthesis of the archetypal alkaloid of this family, (+)-aspidospermidine, and an A-ring-oxygenated derivative, (+)-deacetylaspidospermine, the precursor to (-)-vallesine, from a common intermediate.
Collapse
|
40
|
Additive-Free Pd-Catalysed C-2 Arylation of Tryptophan Derivatives with Diaryliodonium Salts. JOURNAL OF CHEMICAL RESEARCH 2018. [DOI: 10.3184/174751918x15232701502261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
An efficient, mild and Pd-catalysed C-2 arylation of Fmoc-L-tryptophan with diaryliodonium salts has been developed, giving easy access to C-2 arylated tryptophan derivatives. This protocol tolerates a variety of functional groups and proceeds smoothly in high yields without any additives. In addition, the chemoseletive C–H arylation with unsymmetrical salts is described.
Collapse
|
41
|
Abstract
The total synthesis of tambromycin (1), a recently isolated tetrapeptide, is reported. This unusual natural product possesses a highly modified tryptophan-derived indole fragment fused to an α-methylserine-derived oxazoline ring, and a unique noncanonical amino acid residue named tambroline (11). A convergent synthesis of tambromycin was achieved by a 13-step route that leveraged recent developments in the field of C-H functionalization to prepare the complex indole fragment, as well as an efficient synthesis of tambroline that featured a diastereoselective amination of homoproline.
Collapse
|
42
|
Rhodium(III)-Catalyzed Regioselective Direct C4-Alkylation and C2-Annulation of Indoles: Straightforward Access to Indolopyridone. European J Org Chem 2018. [DOI: 10.1002/ejoc.201701755] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
43
|
Regio and Enantioselective Organocatalytic Friedel-Crafts Alkylation of 4-Aminoindoles at the C7-Position. Org Lett 2018; 20:590-593. [PMID: 29341624 DOI: 10.1021/acs.orglett.7b03703] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
A chiral phosphoric acid catalyzed highly regio- and enantioselective Friedel-Crafts alkylation at the indole C7-position was developed via the introduction of an alkylamine moiety at the C4-position of the indole ring. The methodology is applicable to a wide range of 4-aminoindoles and β,γ-unsaturated α-ketimino esters to furnish the corresponding C7-position functionalized chiral indole derivatives in high yields with moderate to excellent enantioselectivities. Furthermore, the α-ketimino ester moiety in the products is a versatile building block and enables many further transformations.
Collapse
|
44
|
Abstract
Recent advances in transition metal-catalyzed selective C–H functionalization of indoles have garnered tremendous attention.
Collapse
|
45
|
|
46
|
Discovery of 7-[18F]Fluorotryptophan as a Novel Positron Emission Tomography (PET) Probe for the Visualization of Tryptophan Metabolism in Vivo. J Med Chem 2017; 61:189-206. [DOI: 10.1021/acs.jmedchem.7b01245] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
|
47
|
Rhodium-Catalyzed Site-Selective Coupling of Indoles with Diazo Esters: C4-Alkylation versus C2-Annulation. Org Lett 2017; 19:6184-6187. [DOI: 10.1021/acs.orglett.7b03099] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
48
|
|
49
|
Iridium-Catalyzed Direct Regioselective C4-Amidation of Indoles under Mild Conditions. Org Lett 2017; 19:2502-2505. [DOI: 10.1021/acs.orglett.7b00730] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
50
|
|