scholarly journals Rhodium-catalyzed intermolecular enantioselective Alder–ene type reaction of cyclopentenes with silylacetylenes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Dongquan Zhang ◽  
Miaomiao Li ◽  
Jiajia Li ◽  
Aijun Lin ◽  
Hequan Yao
Keyword(s):  
Natural Products ◽  
Quaternary Carbon ◽  
Type Reaction ◽  
Economic Method ◽  
Migratory Insertion ◽  
Tertiary Carbon ◽  
High Yields

AbstractThe Alder–ene type reaction between alkenes and alkynes provides an efficient and atom-economic method for the construction of C-C bond, which has been widely employed in the synthesis of natural products and other functional molecules. The intramolecular enantioselective Alder-ene cycloisomerization reactions of 1,n-enynes have been extensively investigated. However, the intermolecular asymmetric version has not been reported, and remains a challenging task. Herein, we describe a rhodium-catalyzed intermolecular enantioselective Alder-ene type reaction of cyclopentenes with silylacetylenes. A variety of chiral (E)-vinylsilane tethered cyclopentenes bearing one quaternary carbon and one tertiary carbon stereocenters are achieved in high yields and enantioselectivities. The reaction undergoes carbonyl-directed migratory insertion, β-H elimination and desymmetrization of prochiral cyclopentenes processes.

Tin(II)chloride Mediated Addition Reaction of Bromonitromethane to Aldehydes

2005 ◽  
Vol 60 (4) ◽  
pp. 416-418 ◽  
Author(s):  
Ali S. Mahasneh
Keyword(s):  
Mass Spectroscopy ◽  
Elemental Analysis ◽  
Addition Reaction ◽  
Aromatic Aldehydes ◽  
Aliphatic Aldehydes ◽  
Type Reaction ◽  
High Yields

Bromonitromethane adds to aliphatic aldehydes in the presence of tin(II) chloride to yield β -nitro alcohols via a Reformatsky-type reaction in high yields, while aromatic aldehydes give low yields. The products were characterized by IR, NMR, and mass spectroscopy and by elemental analysis

Concise Synthesis of Tryptanthrin Spiro Analogues with In Vitro Antitumor Activity Based on One-Pot, Three-Component 1,3-Dipolar Cycloaddition of Azomethine Ylides to Сyclopropenes

Synthesis ◽  
2018 ◽  
Vol 51 (03) ◽  
pp. 713-729 ◽  
Author(s):  
Vitali Boitsov ◽  
Alexander Stepakov ◽  
Alexander Filatov ◽  
Nickolay Knyazev ◽  
Stanislav Shmakov ◽  
...  
Keyword(s):  
Antitumor Activity ◽  
Azomethine Ylides ◽  
Azomethine Ylide ◽  
Dipolar Cycloaddition ◽  
One Pot ◽  
Economic Method ◽  
Reaction Proceeds ◽  
High Yields

A simple, efficient and atom-economic method has been developed for the synthesis of complex alkaloid-like compounds with spiro-fused indolo[2,1-b]quinazoline and cyclopropa[a]pyrrolizine or 3-azabicyclo[3.1.0]hexane moieties. We have found that one-pot, three-component 1,3-dipolar cycloaddition reactions allow the desired products to be obtained from various cyclopropene derivatives with tryptanthrin-derived azomethine ylides generated in situ, in good to high yields and excellent diastereoselectivity. The possibility of ylide generation was exemplified by using α-amino acids (l-proline, l-4-thiazolidincarboxylic acid) and simplest peptides (dipeptide Gly-Gly, tripeptide Gly-Gly-Gly). Quantum chemical investigations indicate that the reaction proceeds through the S-shaped azomethine ylide, the interaction of which with cyclopropenes proceeds via a less sterically hindered endo-transition state. The antitumor activity of some of spiro-tryptanthrin derivatives against erythroleukemia (K562), cervical carcinoma (HeLa) and colon carcinoma (CT26) cell lines was evaluated in vitro by MTS-assay.

Aldol-type reaction of a 4-pyrone: a straightforward approach to 4-pyrone-containing natural products

2009 ◽  
Vol 50 (3) ◽  
pp. 325-328 ◽  
Author(s):  
Tetsuya Sengoku ◽  
Takuma Takemura ◽  
Emi Fukasawa ◽  
Ichiro Hayakawa ◽  
Hideo Kigoshi
Keyword(s):  
Natural Products ◽  
Type Reaction ◽  
Straightforward Approach

scholarly journals Iodine-catalyzed electrophilic substitution of indoles: Synthesis of (un)symmetrical diindolylmethanes with a quaternary carbon center

2021 ◽  
Vol 17 ◽  
pp. 1464-1475
Author(s):  
Thanigaimalai Pillaiyar ◽  
Masoud Sedaghati ◽  
Andhika B. Mahardhika ◽  
Lukas L. Wendt ◽  
Christa E. Müller
Keyword(s):  
Neurodegenerative Diseases ◽  
Drug Targets ◽  
Electrophilic Substitution ◽  
Cannabinoid Receptors ◽  
Quaternary Carbon ◽  
Mild Conditions ◽  
Biological Studies ◽  
High Yields

A novel, versatile approach for the synthesis of unsymmetrical 3,3'-diindolylmethanes (DIMs) with a quaternary carbon center has been developed via iodine-catalyzed coupling of trifluoromethyl(indolyl)phenylmethanols with indoles. In contrast to previously reported methods, the new procedure is characterized by chemoselectivity, mild conditions, high yields, and scalability to obtain gram amounts for biological studies. Selected compounds were found to display affinity for cannabinoid receptors, which are promising drug targets for the treatment of inflammatory and neurodegenerative diseases.

scholarly journals Tyrosine and Drug-like Late-stage Benzylic Functionalization via Photoredox Catalysis

2020 ◽  
Author(s):  
Tobias Brandhofer ◽  
Volker Derdau ◽  
María Mendez ◽  
Christoph Pöverlein ◽  
Olga Garcia Mancheno
Keyword(s):  
Natural Products ◽  
Visible Light ◽  
Late Stage ◽  
Medicinal Chemistry ◽  
Functional Group ◽  
Reaction Conditions ◽  
Site Selectivity ◽  
Wide Range ◽  
High Yields ◽  
Therapeutic Compounds

Abstract Visible light mediated late-stage functionalization is a rising field in synthetic and medicinal chemistry, allowing the fast and diversified modification of valuable, potentially therapeutic compounds such as peptides. However, there are relatively few mild methodologies for the C(sp3)-H functionalization of complex peptides. Herein, we report a visible light mediated photocatalytic protocol for the benzylic C-H modification of tyrosine and related C-H bonds. The embraced radical-cation/deprotonation strategy enables an incorporation of a wide range of valuable functional groups in high yields and chemoselectivity. The mild reaction conditions, site-selectivity and high functional group tolerance was highlighted by the functionalization of complex peptides, drugs and natural products, providing a promising synthetic platform in medicinal chemistry.

scholarly journals Co-Catalyzed E-(β)-Selective Hydrogermylation of Terminal Alkynes

2021 ◽  
Author(s):  
Maxim Radzhabov ◽  
Neal Mankad
Keyword(s):  
Natural Products ◽  
Late Stage ◽  
Functional Group ◽  
Terminal Alkynes ◽  
Mechanistic Studies ◽  
Practical Utility ◽  
Π Complex ◽  
Accessible Method ◽  
High Yields

<a></a><a>We demonstrated unprecedentedly that Co complexes can catalyze hydrogermylation of alkynes. Subsequently, a selective, accessible method was developed to synthesize E-(β)-vinyl(trialkyl)germanes from various terminal alkynes with high yields. As shown on multiple examples, the developed method demonstrates broad functional group tolerance and practical utility for late-stage hydrogermylation of drugs and natural products. The method is compatible with alkynes bearing both aryl and alkyl substituents, providing unrivaled selectivity for previously challenging 1° alkyl-substituted alkynes. Moreover, the catalyst used in this method, Co<sub>2</sub>(CO)<sub>8</sub>, is a cheap and commercially available reagent. Conducted mechanistic studies supported syn-addition of Bu<sub>3</sub>GeH to an alkyne</a> π-complex.

scholarly journals Tailoring Tryptophan Synthase TrpB for Selective Quaternary Carbon Bond Formation

2019 ◽  
Author(s):  
Markus Dick ◽  
Nicholas S. Sarai ◽  
Michael W. Martynowycz ◽  
Tamir Gonen ◽  
Frances H. Arnold
Keyword(s):  
Condensation Reaction ◽  
Bond Formation ◽  
Tryptophan Synthase ◽  
Indole Derivatives ◽  
Quaternary Carbon ◽  
Noncanonical Amino Acids ◽  
Carbon Bond ◽  
E Coli ◽  
Tertiary Carbon ◽  
Quaternary Stereocenters

<div><div><div><p>We previously engineered the tryptophan synthase beta-subunit (TrpB), which catalyzes the condensation reaction between L-serine and indole to form L-tryptophan, to synthesize a range of modified tryptophans from serine and indole derivatives. In this study, we used directed evolution to engineer TrpB to accept 3-substituted oxindoles and form C–C bonds leading to new quaternary stereocenters. At first, the TrpBs that could use 3-substituted oxindoles preferentially formed N–C bonds by attacking the oxindole N<sub>1 </sub>atom. We found, however, that protecting the nitrogen encouraged evolution towards C-alkylation, which persisted even when this protection was removed. After seven rounds of evolution leading to a 400-fold improvement in activity, variant <i>Pf</i><sub>quat</sub> efficiently alkylates 3-substituted oxindoles to selectively form new stereocenters at the γ-position of the amino acid products. The configuration of the new γ-stereocenter of one of the products was determined from the crystal structure obtained by microcrystal electron diffraction (MicroED). Substrates structurally related to 3-methyloxindole such as lactones and ketones can also be used by the enzyme for quaternary carbon bond formation, where the biocatalyst exhibits excellent regioselectivity for the tertiary carbon atom. Highly thermostable and expressed at > 500 mg/L <i>E. coli</i> culture, TrpB <i>Pf</i><sub>quat </sub>provides an efficient and environmentally-friendly platform for the preparation of noncanonical amino acids bearing quaternary carbons.</p></div></div></div>

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