Redox-Tag-Guided Radical Cation Diels –Alder Reactions: Use of Enol Ethers as Dienophiles
Synlett DOI: 10.1055/a-2161-9607 Although radical cation Diels–Alder reactions enable the formation of cyclohexene ring systems between electronically mismatched (both electron-rich) dienes and dienophiles, which is otherwise difficult or impossible to achieve under thermal conditions, the substrate scope has been limited. Herein, we disclose that a radical cation Diels–Alder reaction using an enol ether as an electron-rich (and therefore oxidizable) dienophile is possible through a rationally designed redox tag strategy. Electrochemical and TiO2 photochemical approaches are effective in driving the reaction, where bot...
Source: Synlett - October 23, 2023 Category: Chemistry Authors: Morizumi, Haruka Nakayama, Kaii Kitano, Yoshikazu Okada, Yohei Tags: cluster Source Type: research
Chiral Betaine-Mediated Efficient Organocatalytic Asymmetric Isomerization of β,γ-Unsaturated Butenolides
Synlett DOI: 10.1055/s-0042-1751496 An asymmetric isomerization of β,γ-unsaturated butenolides with a newly developed betaine catalyst at a 0.2–2 mol% loading, an improvement upon available methods that use 0.5–2.0 mol% catalyst. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals: Table of contents | Abstract | Full text (Source: Synlett)
Source: Synlett - October 20, 2023 Category: Chemistry Authors: Zeng, Yiqun Fei, Chao Zhou, Xiao Luo, Jisheng Deng, Li Tags: cluster Source Type: research
A Facile Synthesis of 3 ′-Fluoro Hexitol Adenosine and Guanosine Phosphoramidites
We report a convenient and scalable synthetic approach for the synthesis of 3′-fluoro hexitol adenosine and guanosine nucleoside analogues and corresponding phosphoramidites in good yield. 1,5-Anhydro-4,6-O-benzylidene-d-glucitol was converted into 1,5-anhydro-4,6-O-benzylidene-3-deoxy-3-fluoro-2-O-trifluoromethanesulfonyl-d-altritol in a three-step process. Glycosylation using adenosine or 2-amino-6-iodopurine yielded the corresponding nucleoside analogues in excellent yield. Based on this strategy, a highly concise and scalable synthesis of 3′-fluoro hexitol purine nucleosides (1–2 g, 18–21% overall yield) was ac...
Source: Synlett - October 19, 2023 Category: Chemistry Authors: Prakash, Thazha P. Yu, Jinghua Vasquez, Guillermo Allerson, Charels R. Swayze, Eric E. Tags: cluster Source Type: research
Chiral Bifunctional Sulfide-Catalyzed Enantioselective Synthesis of α-Substituted γ-Lactones Bearing a γ-Quaternary Stereocenter
Synlett DOI: 10.1055/a-2161-9513 Catalytic highly enantioselective syntheses of α-spiro-γ-lactones and α-substituted γ-lactones bearing a γ-quaternary stereocenter have been achieved through chiral bifunctional sulfide-catalyzed asymmetric bromolactonizations. The synthetic utility of the optically active γ-lactone products was demonstrated by transformations into functionalized γ-lactones and epoxides possessing a quaternary stereocenter. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals: Table of contents | Abstract | Full text (Source: Synlett)
Source: Synlett - October 19, 2023 Category: Chemistry Authors: Mori, Taiki Sumida, Sao Furuya, Yasuaki Shirakawa, Seiji Tags: cluster Source Type: research
Synthesis and Properties of 2 ′-Deoxyadenosine Mimics Bearing a Thieno[3,2-d]pyrimidine Ring
In this study, two adenosine-like C-nucleosides (dSA and dSO2A) bearing thieno[3,2-d]pyrimidine rings were designed and synthesized. These analogues were synthesized via the Heck reaction, and their properties as monomer nucleosides were investigated. Both the dSA and dSO2A monomers were not recognized by adenosine deaminase (ADA). In addition, they exhibited fluorescence emissions in the UV and visible regions of dSA and dSO2A, respectively. Subsequently, dSA was converted into a phosphoramidite compound and incorporated into the ONs. The synthesized dSA-modified ONs formed a stable duplex with DNA and RNA complements com...
Source: Synlett - October 18, 2023 Category: Chemistry Authors: Fuchi, Yasufumi Kawaguchi, Miho Ito, Yuta Hari, Yoshiyuki Tags: letter Source Type: research
Serendipitous Synthesis of 5-Hydroxyuridine from 2 ′,3′-O-Isopropylidene N4-Acetylcytidine by Hypervalent Iodine(III)-Mediated Reaction
Synlett DOI: 10.1055/a-2174-2554 Whereas BAIB-TEMPO oxidation of 2′,3′-O-TBDMS-N4-acetylcytidine results in the expected 5′-carboxylic acid nucleoside, its 2′,3′-O-isopropylidene analogue reacts in a radically different way. We have demonstrated here that hypervalent iodine(III) in water triggers an unprecedented oxidative cyclization leading to a mixture of C5-substituted O6,5′-cyclo-5,6-dihydrouridines. This mixture of cyclouridines can be opened under basic conditions and, after deprotection, yields 5-hydroxyuridine, an important post-transcriptional modification of uridine at the wobble position (U34) of ba...
Source: Synlett - October 18, 2023 Category: Chemistry Authors: Maverick, Mary Anne No ël, Mathieu Vasseur, Jean-Jacques Baraguey, Carine Debart, Fran çoise Smietana, Michael Tags: cluster Source Type: research
Decagram-Scale Synthesis of N-{2-[4-( β-d-Glucopyranosyloxy)-2-methylphenyl]-1,1-dimethyl-2-oxoethyl}-3-methylthiophene-2-carboxamide (GPTC), a Metabolite of the Fungicide Isofetamid
Synlett DOI: 10.1055/a-2178-1442 A decagram-scale synthesis of N-{2-[4-(β-d-glucopyranosyloxy)-2-methylphenyl]-1,1-dimethyl-2-oxoethyl}-3-methylthiophene-2-carboxamide (GPTC), a metabolite of the fungicide isofetamid, has been achieved in a highly straightforward manner from the known compound 1-(4-hydroxy-2-methylphenyl)-2-methylpropan-1-one in eight steps with a 20% overall yield to provide a standard certified reference material for residue analysis in food. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals: Table of contents | Abstract | Full text (Source: Synlett)
Source: Synlett - October 17, 2023 Category: Chemistry Authors: Jang, Hongjun Kwak, Soo Yeon Kim, Young Hoon Han, Jae-hyuk Park, Youngjik Baek, Seung-Hoon Lee, Dongjoo Kim, Hyoungsu Tags: letter Source Type: research
Stereogenic π-Conjugated Macrocycles: Synthesis, Structure, and Chiroptical Properties Including Circularly Polarized Luminescence
Synlett DOI: 10.1055/a-2158-8820 Highly symmetrical and aesthetically pleasing molecules have attracted the attention of organic chemists. We synthesized new highly symmetric stereogenic π-conjugated macrocycles with planar or axial chirality. Macrocyclic oligomers synthesized by Yamamoto coupling or Suzuki–Miyaura cross-coupling from the π-unit containing chirality. These cyclization reactions gave multiple oligomers in relatively high yields. We then elucidated their structures and investigated their chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL). Because of the ...
Source: Synlett - October 16, 2023 Category: Chemistry Authors: Hasegawa, Masashi Mazaki, Yasuhiro Tags: account Source Type: research
Additive-Free Copper-Catalyzed Benzylic C(sp3) –H Carbamation: Simple Preparation of Primary Benzylic Amines
Synlett DOI: 10.1055/a-2170-2630 A simple and practical method for the synthesis of primary alkylamines by direct functionalization of hydrocarbons is described. The N-Boc-protected alkylamines are readily prepared from tert-butyl (trimethylsilyl)carbamate and N-fluorobenzenesulfonimide in the presence of a Cu(I) catalyst at low catalyst loadings. Advantageously, this process proceeds free of any additive such as auxiliary bases/acids, requires only one equivalent of the substrate, and does not require ligand synthesis. This operationally simple C–H carbamation method shows high site selectivity and good functional-group...
Source: Synlett - October 12, 2023 Category: Chemistry Authors: Schmidt, William Bakhoda, Abolghasem Gus Tags: letter Source Type: research
Boryl Acrylaldehyde: An Elusive Member of the α-Boryl Aldehyde Class of Reagent
We describe a synthetic route to boryl acrylaldehyde, an amphoteric molecule that features BMIDA and aldehyde functionalities attached to an sp2-carbon center. As the project unfolded, conventional protocols based on aldol condensation turned out to be unsuccessful. We eventually zeroed in on oxidative conditions that preserved the BMIDA group and delivered the desired aldehyde functionality. During our investigation, it became clear that boryl alcohol displays hemilabile N–B bonding, which differs dramatically from the previously described congeners with the sp3-carbon center connected to boron. We have attempted to und...
Source: Synlett - October 12, 2023 Category: Chemistry Authors: Trofimova, Alina Brien, Chelsey Trinchera, Piera Tien, Chieh-Hung Yudin, Andrei K. Tags: cluster Source Type: research
Nickel-Catalyzed Decarbonylation of α-Oxyacetic Acid Thioesters: Hydroxymethylation of Mercaptans
Synlett DOI: 10.1055/a-2159-4369 A strategy for the Ni-catalyzed decarbonylation of α-oxyacetic acid thioesters is described, providing a new pathway for the synthesis of monosulfide acetals, and further proving that oxygen atoms can stabilize an α-carbocation and promote a decarbonylation reaction. This method has good functional-group compatibility and can tolerate a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents. In addition, this method complements the conventional cross-coupling reactions. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Th...
Source: Synlett - October 11, 2023 Category: Chemistry Authors: Tian, Rui Li, Jia-Xin Zhu, Yong-Ming Tags: letter Source Type: research
Sulfonated Graphene as a Sustainable Catalyst for Environmentally Benign Preparation of Benzylidene Acetals of Carbohydrates
Synlett DOI: 10.1055/a-2166-0400 A clean and efficient method has been developed for the introduction of benzylidene acetals into carbohydrate derivatives catalyzed by sulfonated graphene at room temperature. Yields were excellent in each case. The catalyst can be reused several times without much decrease in reactivity. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals: Table of contents | Abstract | Full text (Source: Synlett)
Source: Synlett - October 11, 2023 Category: Chemistry Authors: Rabha, Padmashri Sharma, Anjali Panchadhayee, Rajib Tags: letter Source Type: research
Solvent Selection in the Detritylation Reaction for the Solid-Phase Synthesis of Oligonucleotides
This study examined the choice of solvent in the detritylation reaction for solid-phase oligonucleotide synthesis. In addition to being chemically inert under detritylation conditions, such a solvent should not bind with acid used in this reaction. These considerations explained the only two choices of solvent currently used in the detritylation reaction: dichloromethane and toluene. Other solvents, such as ethyl acetate, acetonitrile, THF, and nitromethane are shown by NMR spectroscopy to bind with trichloroacetic acid. Therefore, these are undesirable solvents for the detritylation reaction, confirmed by solid-phase synt...
Source: Synlett - October 11, 2023 Category: Chemistry Authors: Li, Quanjian Sanghvi, Yogesh S. Yan, Hongbin Tags: letter Source Type: research
A Complementary Route for Alkene –Arene para-Cycloadditions by Visible-Light-Promoted Triplet Sensitization of Allenamides
Synlett DOI: 10.1055/a-2136-3947 The synthetic relevance of bicyclo[2.2.2]octadienes is witnessed by their successful application in various chemical domains, promoting a recurrent interest in the concise assembly of these bridged bicycles. Seminal examples of strategies to craft these compounds are presented, together with more-recent applications that exploit visible light. In this context, a general intramolecular method for the para-cycloaddition of an allenamide arm onto simple aryl rings is highlighted. [...] Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals: Table of cont...
Source: Synlett - October 9, 2023 Category: Chemistry Authors: Serafino, Andrea Maestri, Giovanni Tags: synpacts Source Type: research
A Simple and Powerful tert-Butylation of Carboxylic Acids and Alcohols
Synlett DOI: 10.1055/a-2161-9689 A simple and safe tert-butylation reaction was developed. Treatment of various free amino acids with 1.1 equivalents of bis(trifluoromethanesulfonyl)imide in tert-butyl acetate directly afforded tert-butyl esters with free amino groups quickly and in good yields. In addition, various carboxylic acids and alcohols without amino groups were converted into tert-butyl esters and ethers, respectively, in high yields in the presence of small catalytic amounts of bis(trifluoromethanesulfonyl)imide. All tert-butylation reactions of free amino acids, carboxylic acids, and alcohols proceeded much fas...
Source: Synlett - October 9, 2023 Category: Chemistry Authors: Ogasa, Chie Kayano, Kimika Namba, Kosuke Tags: letter Source Type: research
