1
|
Variation of terpene alkaloids in Daphniphyllum macropodum across plants and tissues. THE NEW PHYTOLOGIST 2024. [PMID: 38757546 DOI: 10.1111/nph.19814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2024] [Accepted: 04/28/2024] [Indexed: 05/18/2024]
Abstract
Daphniphyllum macropodum produces alkaloids that are structurally complex with polycyclic, stereochemically rich carbon skeletons. Understanding how these compounds are formed by the plant may enable exploration of their biological function and bioactivities. We employed multiple metabolomics techniques, including a workflow to annotate compounds in the absence of standards, to compare alkaloid content across plants and tissues. Different alkaloid structural types were found to have distinct distributions between genotypes, between tissues and within tissues. Alkaloid structural types also showed different isotope labelling enrichments that matched their biosynthetic relationships. The work suggests that mevalonate derived 30-carbon alkaloids are formed in the phloem region before their conversion to 22-carbon alkaloids which accumulate in the epidermis. This sets the stage for further investigation into the biosynthetic pathway.
Collapse
|
2
|
Cascade ring expansion reactions for the synthesis of medium-sized rings and macrocycles. Chem Commun (Camb) 2024; 60:4999-5009. [PMID: 38655659 DOI: 10.1039/d4cc01303d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
This Feature Article discusses recent advances in the development of cascade ring expansion reactions for the synthesis of medium-sized rings and macrocycles. Cascade ring expansion reactions have much potential for use in the synthesis of biologically important medium-sized rings and macrocycles, most notably as they don't require high dilution conditions, which are commonly used in established end-to-end macrocyclisation methods. Operation by cascade ring expansion method can allow large ring products to be accessed via rearrangements that proceed exclusively by normal-sized ring cyclisation steps. Ensuring that there is adequate thermodynamic driving force for ring expansion is a key challenge when designing such methods, especially for the expansion of normal-sized rings into medium-sized rings. This Article is predominantly focused on methods developed in our own laboratory, with selected works by other groups also discussed. Thermodynamic considerations, mechanism, reaction design, route planning and future perspective for this field are all covered.
Collapse
|
3
|
Unspecific Peroxygenase (UPO) can be Tuned for Oxygenation or Halogenation Activity by Controlling the Reaction pH. Chemistry 2024:e202401706. [PMID: 38700372 DOI: 10.1002/chem.202401706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/02/2024] [Accepted: 05/03/2024] [Indexed: 05/05/2024]
Abstract
Unspecific Peroxygenases (UPOs) are increasingly significant enzymes for selective oxygenations as they are stable, highly active and catalyze their reactions at the expense of only hydrogen peroxide as the oxidant. Their structural similarity to chloroperoxidase (CPO) means that UPOs can also catalyze halogenation reactions based upon the generation of hypohalous acids from halide and H2O2. Here we show that the halogenation and oxygenation modes of a UPO can be stimulated at different pH values. Using simple aromatic compounds such as thymol, we show that, at a pH of 3.0 and 6.0, either brominated or oxygenated products respectively are produced. Preparative 100 mg scale transformations of substrates were performed with 60-72 % isolated yields of brominated products obtained. A one-pot bromination-oxygenation cascade reaction on 4-ethylanisole, in which the pH was adjusted from 3.0 to 6.0 at the halfway stage, yielded sequentially brominated and oxygenated products 1-(3-bromo-4-methoxyphenyl)ethyl alcohol and 3-bromo-4-methoxy acetophenone with 82 % combined conversion. These results identify UPOs as an unusual example of a biocatalyst that is tunable for entirely different chemical reactions, dependent upon the reaction conditions.
Collapse
|
4
|
Expanding the scope of the successive ring expansion strategy for macrocycle and medium-sized ring synthesis: unreactive and reactive lactams. Org Biomol Chem 2024; 22:2985-2991. [PMID: 38526035 DOI: 10.1039/d4ob00285g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
New methods are described that expand the scope of the Successive Ring Expansion (SuRE) with respect to synthetically challenging lactams. A protocol has been developed for use with 'unreactive' lactams, enabling SuRE reactions to be performed on subsrates that fail under previously established conditions. Ring expansion is also demonstarted on 'reactive' lactams derived from iminosugars for the first time. The new SuRE methods were used to prepare a diverse array of medium-sized and macrocyclic lactams and lactones, which were evaluted in an anti-bacterial assay against E. coli BW25113WT.
Collapse
|
5
|
The genomic and enzymatic basis for iridoid biosynthesis in cat thyme (Teucrium marum). THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2024. [PMID: 38489316 DOI: 10.1111/tpj.16698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Revised: 01/30/2024] [Accepted: 02/14/2024] [Indexed: 03/17/2024]
Abstract
Iridoids are non-canonical monoterpenoids produced by both insects and plants. An example is the cat-attracting and insect-repelling volatile iridoid nepetalactone, produced by Nepeta sp. (catmint) and aphids. Recently, both nepetalactone biosynthetic pathways were elucidated, showing a remarkable convergent evolution. The iridoid, dolichodial, produced by Teucrium marum (cat thyme) and multiple insect species, has highly similar properties to nepetalactone but its biosynthetic origin remains unknown. We set out to determine the genomic, enzymatic, and evolutionary basis of iridoid biosynthesis in T. marum. First, we generated a de novo chromosome-scale genome assembly for T. marum using Oxford Nanopore Technologies long reads and proximity-by-ligation Hi-C reads. The 610.3 Mb assembly spans 15 pseudomolecules with a 32.9 Mb N50 scaffold size. This enabled identification of iridoid biosynthetic genes, whose roles were verified via activity assays. Phylogenomic analysis revealed that the evolutionary history of T. marum iridoid synthase, the iridoid scaffold-forming enzyme, is not orthologous to typical iridoid synthases but is derived from its conserved paralog. We discovered an enzymatic route from nepetalactol to diverse iridoids through the coupled activity of an iridoid oxidase cytochrome P450 and acetyltransferases, via an inferred acylated intermediate. This work provides a genomic resource for specialized metabolite research in mints and demonstration of the role of acetylation in T. marum iridoid diversity. This work will enable future biocatalytic or biosynthetic production of potent insect repellents, as well as comparative studies into iridoid biosynthesis in insects.
Collapse
|
6
|
A Modular Strategy for the Synthesis of Macrocycles and Medium-Sized Rings via Cyclization/Ring Expansion Cascade Reactions. J Am Chem Soc 2024; 146:5702-5711. [PMID: 38372651 PMCID: PMC10910531 DOI: 10.1021/jacs.4c00659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 01/31/2024] [Accepted: 02/01/2024] [Indexed: 02/20/2024]
Abstract
Macrocycles and medium-sized rings are important in many scientific fields and technologies but are hard to make using current methods, especially on a large scale. Outlined herein is a strategy by which functionalized macrocycles and medium-sized rings can be prepared using cyclization/ring expansion (CRE) cascade reactions, without resorting to high dilution conditions. CRE cascade reactions are designed to operate exclusively via kinetically favorable 5-7-membered ring cyclization steps; this means that the problems typically associated with classical end-to-end macrocyclization reactions are avoided. A modular synthetic approach has been developed to facilitate the simple assembly of the requisite linear precursors, which can then be converted into an extremely broad range of functionalized macrocycles and medium-sized rings using one of nine CRE protocols.
Collapse
|
7
|
Divergent Cascade Ring-Expansion Reactions of Acryloyl Imides. Chemistry 2024; 30:e202303270. [PMID: 37987097 DOI: 10.1002/chem.202303270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/16/2023] [Accepted: 11/21/2023] [Indexed: 11/22/2023]
Abstract
Macrocyclic and medium-sized ring ketones, lactones and lactams can all be made from common acryloyl imide starting materials through divergent, one-pot cascade ring-expansion reactions. Following either conjugate addition with an amine or nitromethane, or osmium(VIII)-catalysed dihydoxylation, rearrangement through a four-atom ring expansion takes place spontaneously to form the ring expanded products. A second ring expansion can also be performed following a second iteration of imide formation and alkene functionalisation/ring expansion. In the dihydroxylation series, three- or four-atom ring expansion can be performed selectively, depending on whether the reaction is under kinetic or thermodynamic control.
Collapse
|
8
|
Ring expansion reactions of PO-containing molecules. Chem Commun (Camb) 2023. [PMID: 37278604 DOI: 10.1039/d3cc02087h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A series of ring expansion reactions of PO-containing molecules have been developed for the synthesis of medium-sized ring cyclic phosphonate esters and phosphonamidates. The reactivity trends initially appear to be counter-intuitive, compared with more well established ring expansion reactions of lactam derivatives, but are explained by considering the differences in heteroatom bonding to P and C respectively.
Collapse
|
9
|
Ring Expansion Strategies for the Synthesis of Medium Sized Ring and Macrocyclic Sulfonamides. Angew Chem Int Ed Engl 2023; 62:e202217178. [PMID: 36716014 DOI: 10.1002/anie.202217178] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/16/2023] [Accepted: 01/30/2023] [Indexed: 01/31/2023]
Abstract
Two new ring expansion strategies are reported for the synthesis of medium sized ring and macrocyclic sulfonamides. Both methods can be performed without using classical protecting groups, with the key ring expansion step initiated by nitro reduction and amine conjugate addition respectively. Each method can be used to make diversely functionalised cyclic sulfonamides in good to excellent yields, in a range of ring sizes. The ring size dependency of the synthetic reactions is in good agreement with the outcomes modelled by Density Functional Theory calculations.
Collapse
|
10
|
Preparative-Scale Biocatalytic Oxygenation of N-Heterocycles with a Lyophilized Peroxygenase Catalyst. Angew Chem Int Ed Engl 2023; 62:e202214759. [PMID: 36453718 PMCID: PMC10107140 DOI: 10.1002/anie.202214759] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/17/2022] [Accepted: 11/30/2022] [Indexed: 12/02/2022]
Abstract
A lyophilized preparation of an unspecific peroxygenase variant from Agrocybe aegerita (rAaeUPO-PaDa-I-H) is a highly effective catalyst for the oxygenation of a diverse range of N-heterocyclic compounds. Scalable biocatalytic oxygenations (27 preparative examples, ca. 100 mg scale) have been developed across a wide range of substrates, including alkyl pyridines, bicyclic N-heterocycles and indoles. H2 O2 is the only stoichiometric oxidant needed, without auxiliary electron transport proteins, which is key to the practicality of the method. Reaction outcomes can be altered depending on whether hydrogen peroxide was delivered by syringe pump or through in situ generation using an alcohol oxidase from Pichia pastoris (PpAOX) and methanol as a co-substrate. Good synthetic yields (up to 84 %), regioselectivity and enantioselectivity (up to 99 % ee) were observed in some cases, highlighting the promise of UPOs as practical, versatile and scalable oxygenation biocatalysts.
Collapse
|
11
|
Comparing the Catalytic and Structural Characteristics of a 'Short' Unspecific Peroxygenase (UPO) Expressed in Pichia pastoris and Escherichia coli. Chembiochem 2023; 24:e202200558. [PMID: 36374006 PMCID: PMC10098773 DOI: 10.1002/cbic.202200558] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/14/2022] [Indexed: 11/16/2022]
Abstract
Unspecific peroxygenases (UPOs) have emerged as valuable tools for the oxygenation of non-activated carbon atoms, as they exhibit high turnovers, good stability and depend only on hydrogen peroxide as the external oxidant for activity. However, the isolation of UPOs from their natural fungal sources remains a barrier to wider application. We have cloned the gene encoding an 'artificial' peroxygenase (artUPO), close in sequence to the 'short' UPO from Marasmius rotula (MroUPO), and expressed it in both the yeast Pichia pastoris and E. coli to compare the catalytic and structural characteristics of the enzymes produced in each system. Catalytic efficiency for the UPO substrate 5-nitro-1,3-benzodioxole (NBD) was largely the same for both enzymes, and the structures also revealed few differences apart from the expected glycosylation of the yeast enzyme. However, the glycosylated enzyme displayed greater stability, as determined by nano differential scanning fluorimetry (nano-DSF) measurements. Interestingly, while artUPO hydroxylated ethylbenzene derivatives to give the (R)-alcohols, also given by a variant of the 'long' UPO from Agrocybe aegerita (AaeUPO), it gave the opposite (S)-series of sulfoxide products from a range of sulfide substrates, broadening the scope for application of the enzymes. The structures of artUPO reveal substantial differences to that of AaeUPO, and provide a platform for investigating the distinctive activity of this and related'short' UPOs.
Collapse
|
12
|
Preparative‐Scale Biocatalytic Oxygenation of N‐Heterocycles with a Lyophilized Peroxygenase Catalyst. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202214759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
|
13
|
Visible-Light-Mediated Energy Transfer Enables the Synthesis of β-Lactams via Intramolecular Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2022; 61:e202213086. [PMID: 36205440 PMCID: PMC9828223 DOI: 10.1002/anie.202213086] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Indexed: 11/07/2022]
Abstract
The synthesis of 2-azetidinones (β-lactams) from simple acrylamide starting materials by visible-light-mediated energy transfer catalysis is reported. The reaction features a C(sp3 )-H functionalization via a variation of the Norrish-Yang photocyclization involving a carbon-to-carbon 1,5-hydrogen atom transfer (supported by deuterium labelling and DFT calculations) and can be used for the construction of a diverse range of β-lactam products.
Collapse
|
14
|
Visible‐Light Mediated Energy Transfer Enables the Synthesis of β‐Lactams via Intramolecular Hydrogen Atom Transfer. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202213086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
15
|
DFT Studies of Au(I) Catalysed Reactions: Anion Effects and Reaction Selectivity. Isr J Chem 2022. [DOI: 10.1002/ijch.202200033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
16
|
Biocatalytic activation of diazirines for carbene-transfer reactions. Chem 2022. [DOI: 10.1016/j.chempr.2022.06.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
17
|
Strategies for the Synthesis of Heterocyclic Macrocycles and Medium‐Sized Rings. HETEROCYCLES 2022. [DOI: 10.1002/9783527832002.ch3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
18
|
Selectivity, Speciation, and Substrate Control in the Gold-Catalyzed Coupling of Indoles and Alkynes. Organometallics 2022; 41:497-507. [PMID: 35431397 PMCID: PMC9007570 DOI: 10.1021/acs.organomet.2c00035] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Indexed: 11/28/2022]
Abstract
![]()
A convenient
and mild protocol for the gold-catalyzed intermolecular
coupling of substituted indoles with carbonyl-functionalized alkynes
to give vinyl indoles is reported. This reaction affords 3-substituted
indoles in high yield, and in contrast to the analogous reactions
with simple alkynes which give bisindolemethanes,
only a single indole is added to the alkyne. The protocol is robust
and tolerates substitution at a range of positions of the indole and
the use of ester-, amide-, and ketone-substituted alkynes. The use
of 3-substituted indoles as substrates results in the introduction
of the vinyl substituent at the 2-position of the ring. A combined
experimental and computational mechanistic study has revealed that
the gold catalyst has a greater affinity to the indole than the alkyne,
despite the carbon–carbon bond formation step proceeding through
an η2(π)-alkyne complex, which helps to explain
the stark differences between the intra- and intermolecular variants
of the reaction. This study also demonstrated that the addition of
a second indole to the carbonyl-containing vinyl indole products is
both kinetically and thermodynamically less favored than in the case
of more simple alkynes, providing an explanation for the observed
selectivity. Finally, a highly unusual gold-promoted alkyne dimerization
reaction to form a substituted gold pyrylium salt has been identified
and studied in detail.
Collapse
|
19
|
Abstract
Indole-ynones have been established as general substrates for radical dearomatizing spirocyclization cascade reactions. Five distinct and varied synthetic protocols have been developed─cyanomethylation, sulfonylation, trifluoromethylation, stannylation and borylation─using a variety of radical generation modes, ranging from photoredox catalysis to traditional AIBN methods. The simple and easily prepared indole-ynones can be used to rapidly generate diverse, densely functionalized spirocycles and have the potential to become routinely used to explore radical reactivity. Experimental and computational investigations support the proposed radical cascade mechanism and suggest that other new methods are now primed for development.
Collapse
|
20
|
Synthesis of medium-ring lactams and macrocyclic peptide mimetics via conjugate addition/ring expansion cascade reactions. RSC Chem Biol 2022; 3:334-340. [PMID: 35359493 PMCID: PMC8905531 DOI: 10.1039/d1cb00245g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/08/2022] [Indexed: 11/30/2022] Open
Abstract
A novel conjugate addition/ring expansion (CARE) cascade reaction sequence is reported that enables medium-sized ring and macrocyclic bis-lactams to be prepared from primary amines and cyclic imides. The reactions are simple to perform, generally high yielding, and very broad in scope, especially with respect to the primary amine component. CARE reactions can also be performed iteratively, enabling β-peptoid-based macrocyclic peptide mimetics to be ‘grown’ via well controlled, sequential 4-atom ring expansion reactions, with the incorporation of varied functionalised amines during each iteration. A conjugate addition/ring expansion (CARE) cascade reaction sequence is reported that enables medium-sized ring and macrocyclic bis-lactams to be prepared from primary amines and cyclic imides.![]()
Collapse
|
21
|
A Thiol-Mediated Three-Step Ring Expansion Cascade for the Conversion of Indoles into Functionalized Quinolines. Org Lett 2021; 23:2063-2068. [PMID: 33645997 PMCID: PMC8041380 DOI: 10.1021/acs.orglett.1c00205] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2021] [Indexed: 12/02/2022]
Abstract
An operationally simple, high yielding three-step cascade process is described for the direct conversion of indole-tethered ynones into functionalized quinolines. A single "multitasking" thiol reagent is used to promote a three-step dearomatizing spirocyclization, nucleophilic substitution, and one-atom ring expansion reaction cascade under remarkably mild conditions. In addition, a novel route to thio-oxindoles is described, which was discovered by serendipity.
Collapse
|
22
|
Synthesis of macrocyclic and medium-sized ring thiolactones via the ring expansion of lactams. Org Biomol Chem 2021; 19:1404-1411. [PMID: 33491715 DOI: 10.1039/d0ob02502j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A side chain insertion method for the ring expansion of lactams into macrocyclic thiolactones is reported, that can also be incorporated into Successive Ring Expansion (SuRE) sequences. The reactions are less thermodynamically favourable than the analogous lactam- and lactone-forming ring expansion processes (with this notion supported by DFT data), but nonetheless, three complementary protecting group strategies have been developed to enable this challenging transformation to be achieved.
Collapse
|
23
|
Evaluating the Viability of Successive Ring-Expansions Based on Amino Acid and Hydroxyacid Side-Chain Insertion. Chemistry 2020; 26:12674-12683. [PMID: 32432817 PMCID: PMC7589337 DOI: 10.1002/chem.202002164] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Indexed: 01/20/2023]
Abstract
The outcome of ring-expansion reactions based on amino/hydroxyacid side-chain insertion is strongly dependent on ring size. This manuscript, which builds upon our previous work on Successive Ring Expansion (SuRE) methods, details efforts to better define the scope and limitations of these reactions on lactam and β-ketoester ring systems with respect to ring size and additional functionality. The synthetic results provide clear guidelines as to which substrate classes are more likely to be successful and are supported by computational results, using a density functional theory (DFT) approach. Calculating the relative Gibbs free energies of the three isomeric species that are formed reversibly during ring expansion enables the viability of new synthetic reactions to be correctly predicted in most cases. The new synthetic and computational results are expected to support the design of new lactam- and β-ketoester-based ring-expansion reactions.
Collapse
|
24
|
Phosphoranyl Radical Fragmentation Reactions Driven by Photoredox Catalysis. ACS Catal 2020; 10:7250-7261. [PMID: 32905246 PMCID: PMC7469205 DOI: 10.1021/acscatal.0c01923] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 06/04/2020] [Indexed: 12/17/2022]
Abstract
Photocatalytic generation of phosphoranyl radicals is fast emerging as an essential method for the generation of diverse and valuable radicals, typically via deoxygenation or desulfurization processes. This Perspective is a comprehensive evaluation of all studies using phosphoranyl radicals as tunable mediators in photoredox catalysis, highlighting how two distinct methods for phosphoranyl radical formation (radical addition and nucleophilic addition) can be used to generate versatile radical intermediates with diverse reactivity profiles.
Collapse
|
25
|
Abstract
The enantioselective intermolecular C2-allylation of 3-substituted indoles is reported for the first time. This directing group-free approach relies on a chiral Ir-(P, olefin) complex and Mg(ClO4 )2 Lewis acid catalyst system to promote allylic substitution, providing the C2-allylated products in typically high yields (40-99 %) and enantioselectivities (83-99 % ee) with excellent regiocontrol. Experimental studies and DFT calculations suggest that the reaction proceeds via direct C2-allylation, rather than C3-allylation followed by in situ migration. Steric congestion at the indole-C3 position and improved π-π stacking interactions have been identified as major contributors to the C2-selectivity.
Collapse
|
26
|
|
27
|
Abstract
Medium-sized rings have much promise in medicinal chemistry, but are difficult to make using direct cyclisation methods. In this minireview, we highlight the value of ring expansion strategies to address this long-standing synthetic challenge. We have drawn on recent progress (post 2013) to highlight the key reaction design features that enable successful ‘normal-to-medium’ ring expansion for the synthesis of these medicinally important molecular frameworks, that are currently under-represented in compound screening collections and marketed drugs in view of their challenging syntheses. Ring expansion strategies are ideally suited to make synthetically challenging, medium-sized rings with much potential in medicinal chemistry.![]()
Collapse
|
28
|
Abstract
![]()
The polycyclic core of the akuammiline
alkaloids can be synthesized
from simple tryptamine and tryptophol derivatives via a Ag(I)-catalyzed
enantioselective dearomative cyclization cascade sequence. The complex
tetracyclic scaffolds are prepared via a rapid, versatile, three-step
modular synthesis from simple commercially available indole derivatives
in high yields and enantiomeric excess (up to 99% yield and >99% ee).
Collapse
|
29
|
Visible-light-induced intramolecular charge transfer in the radical spirocyclisation of indole-tethered ynones. Chem Sci 2019; 11:1353-1360. [PMID: 34123259 PMCID: PMC8148050 DOI: 10.1039/c9sc05311e] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Indole-tethered ynones form an intramolecular electron donor–acceptor complex that can undergo visible-light-induced charge transfer to promote thiyl radical generation from thiols. This initiates a novel radical chain sequence, based on dearomatising spirocyclisation with concomitant C–S bond formation. Sulfur-containing spirocycles are formed in high yields using this simple and mild synthetic protocol, in which neither transition metal catalysts nor photocatalysts are required. The proposed mechanism is supported by various mechanistic studies, and the unusual radical initiation mode represents only the second report of the use of an intramolecular electron donor–acceptor complex in synthesis. Indole-tethered ynones form an intramolecular electron donor–acceptor complex that can undergo visible-light-induced charge transfer to promote thiyl radical generation from thiols.![]()
Collapse
|
30
|
A marine viral halogenase that iodinates diverse substrates. Nat Chem 2019; 11:1091-1097. [PMID: 31611633 PMCID: PMC6875430 DOI: 10.1038/s41557-019-0349-z] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 09/09/2019] [Indexed: 11/23/2022]
Abstract
Oceanic cyanobacteria are the most abundant oxygen-generating phototrophs on our planet, and therefore, important to life. These organisms are infected by viruses called cyanophages, recently shown to encode metabolic genes that modulate host photosynthesis, phosphorus cycling and nucleotide metabolism. Herein, we report the characterisation of a wild type flavin-dependent viral halogenase (VirX1) from a cyanophage. Notably, halogenases have been previously associated with secondary metabolism, tailoring natural products. Exploration of this viral halogenase reveals it capable of regioselective halogenation of a diverse range of substrates, with a preference for forming aryl iodide species; this has potential implications for the metabolism of the infected host. Until recently, a flavin-dependent halogenase (FDH) capable of iodination in vitro had not been reported. VirX1 is interesting from a biocatalytic perspective showing strikingly broad substrate flexibility, and a clear preference for iodination, as illustrated by kinetic analysis. These factors together render it an attractive tool for synthesis.
Collapse
|
31
|
Internal Nucleophilic Catalyst Mediated Cyclisation/Ring Expansion Cascades for the Synthesis of Medium‐Sized Lactones and Lactams. Angew Chem Int Ed Engl 2019; 58:13942-13947. [DOI: 10.1002/anie.201907206] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Revised: 07/23/2019] [Indexed: 12/12/2022]
|
32
|
Synthetic and Mechanistic Studies into the Rearrangement of Spirocyclic Indolenines into Quinolines. European J Org Chem 2019. [DOI: 10.1002/ejoc.201900798] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|
33
|
Internal Nucleophilic Catalyst Mediated Cyclisation/Ring Expansion Cascades for the Synthesis of Medium‐Sized Lactones and Lactams. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907206] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
34
|
|
35
|
Consecutive Ring-Expansion Reactions for the Iterative Assembly of Medium-Sized Rings and Macrocycles. Synlett 2019. [DOI: 10.1055/s-0037-1611500] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Macrocycles and medium-sized rings have important applications in several scientific fields but can be challenging to make using traditional end-to-end cyclization reactions. Ring-expansion methods represent a useful alternative and offer numerous practical benefits. In this Account, we discuss the current state of the art of ring-expansion strategies that have been applied consecutively. Such methods have the power to expedite the design and synthesis of functionalized macrocycles via the selective, iterative insertion of smaller fragments into ring-enlarged products.1 Introduction2 Insertion Reactions2.1 Transamidation/Transpeptidation2.2 Transesterification2.3 Transthioesterification2.4 Aminyl Radical Cascade2.5 Iterative Synthesis of Lactones2.6 Successive Ring Expansion of β-Ketoesters and Lactams3 Pericyclic Reactions3.1 Sulfur-Mediated Rearrangements3.2 Nitrogen-Mediated Rearrangements4 Fragmentation Reactions5 Conclusions and Future Outlook
Collapse
|
36
|
Merging π-Acid and Pd Catalysis: Dearomatizing Spirocyclization/Cross-Coupling Cascade Reactions of Alkyne-Tethered Aromatics. ACS Catal 2018. [DOI: 10.1021/acscatal.8b03861] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
|
37
|
Iterative Assembly of Macrocyclic Lactones using Successive Ring Expansion Reactions. Chemistry 2018; 24:13947-13953. [PMID: 30011360 PMCID: PMC6334170 DOI: 10.1002/chem.201803064] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 07/12/2018] [Indexed: 12/27/2022]
Abstract
Macrocyclic lactones can be prepared from lactams and hydroxyacid derivatives via an efficient 3- or 4-atom iterative ring expansion protocol. The products can also be expanded using amino acid-based linear fragments, meaning that macrocycles with precise sequences of hydroxy- and amino acids can be assembled in high yields by "growing" them from smaller rings, using a simple procedure in which high dilution is not required. The method should significantly expedite the practical synthesis of diverse nitrogen containing macrolide frameworks.
Collapse
|
38
|
“Back-to-Front” Indole Synthesis Using Silver(I) Catalysis: Unexpected C-3 Pyrrole Activation Mode Supported by DFT. ACS Catal 2018. [DOI: 10.1021/acscatal.8b00745] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
39
|
Dearomatizing Spiroannulation Reagents: Direct Access to Spirocycles from Indoles and Dihalides. Org Lett 2018; 20:3349-3353. [PMID: 29745671 DOI: 10.1021/acs.orglett.8b01248] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Unfunctionalized indoles can be directly converted into 3,3'-spirocyclic indolenines and indolines upon reaction with electrophilic dihalides in the presence of t-BuOK/BEt3. This double C-C bond forming reaction, which simultaneously generates a quaternary spirocyclic center, typically proceeds in high yield and has good functional group tolerance. In contrast to existing dearomatizing spirocyclization approaches, there is no need to prepare a prefunctionalized aromatic precursor, enabling faster access to valuable spirocyclic products from simple, commercially available aromatics in one step.
Collapse
|
40
|
Ag(I)-Catalyzed Synthesis of Azabicyclic Alkaloid Frameworks from Ketimine-Tethered Ynones: Total Synthesis of Indolizidine 209D. Org Lett 2018; 20:1439-1443. [DOI: 10.1021/acs.orglett.8b00225] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
41
|
Synthesis of Cyclic Peptide Mimetics by the Successive Ring Expansion of Lactams. Chemistry 2017; 23:13314-13318. [PMID: 28722215 DOI: 10.1002/chem.201703316] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Indexed: 12/12/2022]
Abstract
A successive ring-expansion protocol is reported that enables the controlled insertion of natural and non-natural amino acid fragments into lactams. Amino acids can be installed into macrocycles via an operationally simple and scalable iterative procedure, without the need for high dilution. This method is expected to be of broad utility, especially for the synthesis of medicinally important cyclic peptide mimetics.
Collapse
|
42
|
Ring-Expansion Reactions in the Synthesis of Macrocycles and Medium-Sized Rings. Chemistry 2017; 23:8780-8799. [DOI: 10.1002/chem.201700467] [Citation(s) in RCA: 147] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Indexed: 01/20/2023]
|
43
|
Ring-Expansion Approach to Medium-Sized Lactams and Analysis of Their Medicinal Lead-Like Properties. Chemistry 2017; 23:2225-2230. [PMID: 27935197 DOI: 10.1002/chem.201605615] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Indexed: 12/20/2022]
Abstract
Medium-sized rings are widely considered to be under-represented in biological screening libraries for lead identification in medicinal chemistry. To help address this, a library of medium-sized lactams has been generated by using a simple, scalable and versatile ring-expansion protocol. Analysis of the library by using open-access computational tool LLAMA suggested that these lactams and their derivatives have highly promising physicochemical and 3D spatial properties and thus have much potential in drug discovery.
Collapse
|
44
|
Selective synthesis of three product classes from imine and carboxylic acid precursors via direct imine acylation. Org Biomol Chem 2017; 15:7527-7532. [DOI: 10.1039/c7ob02039b] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Three divergent procedures allow the selective generation of δ-lactams, β-lactams and tetrahydropyrimidinones from common imine and carboxylic acid precursors.
Collapse
|
45
|
Dearomatisation approaches to spirocyclic dienones via the electrophilic activation of alkynes. Org Biomol Chem 2017; 15:233-245. [DOI: 10.1039/c6ob02426b] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Two simple metal-mediated dearomatising spirocyclisation protocols to generate spirocyclic dienones from anisole and phenol-tethered ynones in high yields are described.
Collapse
|
46
|
Catalytic Dearomatization Approach to Quinolizidine Alkaloids: Five Step Total Synthesis of (±)-Lasubine II. Org Lett 2016; 18:6256-6259. [DOI: 10.1021/acs.orglett.6b03017] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
|
47
|
Preparation and Reactions of Indoleninyl Halides: Scaffolds for the Synthesis of Spirocyclic Indole Derivatives. Org Lett 2016; 18:6328-6331. [DOI: 10.1021/acs.orglett.6b03221] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
48
|
A selective C-H insertion/olefination protocol for the synthesis of α-methylene-γ-butyrolactone natural products. Org Biomol Chem 2016; 14:1641-5. [PMID: 26695888 DOI: 10.1039/c5ob02579f] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A regio- and stereoselective one-pot C-H insertion/olefination protocol has been developed for the late stage installation of α-methylene-γ-butyrolactones into conformationally restricted cyclohexanol-derivatives. The method has been successfully applied in the total synthesis of eudesmanolide natural product frameworks, including α-cyclocostunolide.
Collapse
|
49
|
Silica-Supported Silver Nitrate as a Highly Active Dearomatizing Spirocyclization Catalyst: Synergistic Alkyne Activation by Silver Nanoparticles and Silica. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201608263] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
50
|
Silica-Supported Silver Nitrate as a Highly Active Dearomatizing Spirocyclization Catalyst: Synergistic Alkyne Activation by Silver Nanoparticles and Silica. Angew Chem Int Ed Engl 2016; 55:13798-13802. [DOI: 10.1002/anie.201608263] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Indexed: 01/03/2023]
|