Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• groups, promoter, solvent and temperature has to be applied. In 1981, Mukaiyama et al. introduced glycosyl fluorides [5] as a new class of glycosyl donors [6]. The C–F bond is one of the strongest single bonds in the realm of organic compounds with a bond dissociation energy (BDE) of 570 kJ/mol [7]. Thus

• , often heavy metals; (2) multiple additives (co-promoter, molecular sieves, acid scavenger) to facilitate the reaction and/or suppress formation of side-products; (3) low temperatures; (4) complex experimental procedures. Additionally, the majority of the methods reported to date have been applied only

• . reported a ″green″ glycosylation procedure by employing supercritical CO2 (scCO2) as a weakly Lewis acidic reaction medium [37]. The method was successfully applied for the synthesis of O-glycosides from disarmed glycosyl chlorides and bromides in the absence of additional promoter. Herein we disclose a

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• solvent to successfully furnish 5,6-disubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones 89. Similarly, excellent yields were obtained when the thiol was replaced by malononitrile (51) even in the absence of catalyst or any promoter. The malononitrile undergoes hydrolysis forming an amide, thus giving rise

• (51) and N-alkyl-2-cyanoacetamides 124 as structural units and K2CO3 as base promoter using EtOH as solvent (Scheme 47). The introduction of microwave drastically improved the yield from 65–77% to 81–94% along with reduction in time from 180 min to 15 min when a comparative study with conventional

• -workers [124] by employing aldehydes 5, 5-methyl-3-aminopyrazole (140) and cycloketones 141 as building blocks in a one-pot manner with AcOH and TFA as promoter under microwave irradiation. This method stands out with its high efficiency and shorter reaction time to produce the macrocyclane-fused pyrazolo

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

• and the possible product contamination by homogeneous catalysts [199]. The conventional catalysts for this reaction are EG-soluble metal acetates, the activity of which showed a decrease in the order Zn2+ > Mn2+ > Co2+, which was attributed to the diverse interaction between the metal cation promoter

• and noticeable productivity (TOF = 129 h−1, based on the moles of Zn) at 190°C, EG/PET 4:1, w/w and 5 wt % catalyst [237]. A mechanism was proposed analogous to that depicted in Scheme 6, but in which Zn2+ acts as Lewis acid and dimethylurea acts as base promoter for EG hydroxy deprotonation [238

• view. Some recent examples are cited herein. Postconsumer PET was depolymerised in the melt (at 250 °C) using DEG and Ca/Zn stearate as catalyst, and the product mixture was used in situ in conjunction with bis(2-ethylhexyl)phthalate and the same metal promoter for the production of flexible poly(vinyl

Designed whole-cell-catalysis-assisted synthesis of 9,11-secosterols

• Marek Kõllo,
• Marje Kasari,
• Villu Kasari,
• Tõnis Pehk,
• Ivar Järving,
• Margus Lopp,
• Arvi Jõers and
• Tõnis Kanger

Beilstein J. Org. Chem. 2021, 17, 581–588, doi:10.3762/bjoc.17.52

• IDT codon optimization tool (to eliminate rare codons). Synthetic DNA was ordered from Twist Bioscience and inserted into pET21a backbone as one operon (see Supporting Information File 2) under the control of an IPTG-inducible tac promoter. The obtained plasmid was verified by DNA sequencing. To

Biochemistry of fluoroprolines: the prospect of making fluorine a bioelement

• Vladimir Kubyshkin,
• Rebecca Davis and
• Nediljko Budisa

Beilstein J. Org. Chem. 2021, 17, 439–460, doi:10.3762/bjoc.17.40

• the charged tRNA is to increase the genomic background activity of the ProRS by plasmid-directed coexpression of the native or mutant enzyme by a strong promoter during the incorporation experiment. Early experiments demonstrated sufficient activation of fluoroprolines by ProRS [81]. Conticello et al

Silver-catalyzed synthesis of β-fluorovinylphosphonates by phosphonofluorination of aromatic alkynes

• Yajing Zhang,
• Qingshan Tian,
• Guozhu Zhang and
• Dayong Zhang

Beilstein J. Org. Chem. 2020, 16, 3086–3092, doi:10.3762/bjoc.16.258

• observed. These findings imply that the transformation may involve a radical process rather than an ionic process. On the basis of previous reports [23][24][25][26], we propose a radical mechanism involving the silver promoter, as illustrated in Scheme 5. In this mechanism, Ag(I) was oxidized by

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• variation of structures in guanine-rich DNA sequences [4][5][6], for example, in the promoter regions of oncogenes or in single-stranded overhang of telomeric DNA [7][8][9]. Most notably, it has been shown that quadruplex formation is directly involved in biologically relevant processes [10], for example

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• the addition of boric acid as a promoter, was shown to be most efficient. As found by us, starting from pyrimidone 1а, when reacted with pinacol boronate 6а (1.5 equiv), provided only a minor amount of product 3а (about 9%) under the optimum conditions for the reactions with boronic acids (Table 2

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• from the PK product 41, meaning that the fluoro-PKR does initially take place and that the desired product 41 could be isolated by avoiding the subsequent elimination reaction. This hypothesis was confirmed when the less basic DMSO was used as the promoter instead of NMO, allowing the successful

• isolation of 41 (Scheme 20) [59]. Under the optimized conditions, using stoichiometric Co2(CO)8 and DMSO as the promoter, the process worked well and moderate to good yields were obtained for derivatives 42 bearing aryl substituents at the propargyl moiety, regardless of their electronic nature (Scheme 21

• through an intermolecular Co-mediated PKR of various trifluoromethyl alkynes with 2-norbornene (Scheme 40) [54]. In this process, the authors did not use NMO as a promoter due to its negative effect on the reaction yield. Under the described conditions, the cyclized products 70 were obtained as

Fabclavine diversity in Xenorhabdus bacteria

• Sebastian L. Wenski,
• Harun Cimen,
• Natalie Berghaus,
• Sebastian W. Fuchs,
• Selcuk Hazir and
• Helge B. Bode

Beilstein J. Org. Chem. 2020, 16, 956–965, doi:10.3762/bjoc.16.84

• ), and polyketide synthases (PKS). Selected Xenorhabdus and Photorhabdus mutant strains were generated applying a chemically inducible promoter in front of the suggested fabclavine (fcl) biosynthesis gene cluster (BGC), followed by the analysis of the occurring fabclavines. Subsequently, known and

• modification step (Figure S1, Supporting Information File 1) [25]. Identification of new fabclavine derivatives To analyze the identified fcl BGCs, mutant strains were generated with a chemically inducible promoter in front of fclC or corresponding homologues (Figure 2). The inducible promoter was integrated

• the respective natural product [14]. Initially, the non-induced promoter-exchange mutant was compared with the induced mutant and the wild type to identify signals, related to possible biosynthesis products of the fcl BGCs using the known structure of 1 as a reference [20]. To confirm these signals as

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• to synthesize thiazolidinone derivatives through a Barton–McCombie pathway in 2015 [17] (Scheme 1b). Recently, potassium tert-butoxide has been shown to be an efficient promoter for C–C-bond formation reactions [18][19][20][21][22]. However, only few reports described C–N-bond cross-coupling

• reactions using potassium tert-butoxide as promoter. Wu developed an efficient protocol for the KOt-Bu-promoted synthesis of 1-aminoisoquinolines from 2-methylbenzonitriles and benzonitriles [23], and the carbonylative cyclization of propargylic amines with selenium under CO gas-free conditions [24]. Based

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• in this vital area of research, to our best knowledge, this is the first review that focuses on ortho and para C–H functionalizations by photoredox catalysis to provide atom- and step-economic organic transformations. We are certain that this review will act as a promoter to highlight the application

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• component analysis [140], qPCR/proteomics [141], and iterative grid search [142] to troubleshoot and guide the tuning of the promoter strengths and copy numbers of each module/enzyme (Figure 11b). Toxicity of biosynthetic intermediates, endogenous regulation, and stability of genetic constructs are the main

• promoter is labeled with lower case letters: s: strong and m: medium. This tuning led to 15,000-fold increase in taxatidene titer. c) Two FPP (9)-responsive promoters were implemented to dynamically control the expression of MVA pathway genes and the terpene cyclase gene in order to prevent the

Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

• crucial promoter and the benzothiazoles as the directing groups (Scheme 20). This strategy plays an important role in the pharmaceutical and agrochemical industries. Meanwhile, Xu’s group [59] used O-methyl oxime as the directing group for the Pd-catalyzed ortho-fluorination of aromatic and olefinic C(sp2

• )–H bonds (Scheme 21a). It is worth noting that a cheap and nontoxic nitrate was added as a highly efficient promoter in the presence of NFSI and Pd2(dba)3. In addition, the authors proposed a reaction mechanism that involves a Pd(II)/Pd(IV) catalytic cycle (Scheme 21b). At the early stage of this

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• improvement on this multicomponent approach, making use of β-cyclodextrine as promoter, water as a solvent, and microwave heating (route C, Scheme 16) [98]. Under these neutral conditions, they prepared up to nineteen compounds (60–95%, R1 = H, Cl, R2 = alkyl, benzyl, aryl), including two derivatives

New α- and β-cyclodextrin derivatives with cinchona alkaloids used in asymmetric organocatalytic reactions

• Iveta Chena Tichá,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2019, 15, 830–839, doi:10.3762/bjoc.15.80

• as the promoter (not in a catalytic amount) of a Henry reaction and obtained the product with 99% ee. Subsequently, Doyagüez et al. [17] attached L-proline to β-CD via different linkers (including a triazole linker) and used the resulting organocatalysts in an aldol reaction in water, albeit with a

Sigmatropic rearrangements of cyclopropenylcarbinol derivatives. Access to diversely substituted alkylidenecyclopropanes

• Guillaume Ernouf,
• Jean-Louis Brayer,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2019, 15, 333–350, doi:10.3762/bjoc.15.29

• transformations include the carboxylation of a (trimethylsilylmethyl)cyclopropene in the presence of a fluoride promoter [22], and also the addition of electrophiles to (lithiomethyl)cyclopropenes generated by lithiation of the corresponding methylcyclopropenylsulfone [23] or -sulfoxide [24]. More recently, the

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• used the S. Typhimurium-pJNS25 reporter strain constructed by Smith and Ahmer [27] and also used by Janssens et al. [20] to examine SdiA activity. This strain naturally produces SdiA and contains a reporter plasmid with the promoter region for srgE fused to the luxABCDE operon of V. fischeri (see

• different reporter gene output. E. coli JLD271 is the sdiA mutant of K-12 E. coli [60]. This reporter construct uses an arabinose inducible promoter to produce S. Typhimurium SdiA and the promoter region for srgE fused to lacZ to report SdiA activity. SdiA activity is then measured using standard β

• . E. coli JLD271-pJN105SE-pSC11SE was grown in 10 μg/mL gentamicin and 100 μg/mL ampicillin. Construction of E. coli JLD271-pJN105SE-pSC11SE. The same promoter region used by Smith and Ahmer [27] to construct pJNS25 was used for the promoter region in pSC11SE [66]. 477 base pairs of the srgE (STM1554

Graphitic carbon nitride prepared from urea as a photocatalyst for visible-light carbon dioxide reduction with the aid of a mononuclear ruthenium(II) complex

• Kazuhiko Maeda,
• Daehyeon An,
• Ryo Kuriki,
• Daling Lu and
• Osamu Ishitani

Beilstein J. Org. Chem. 2018, 14, 1806–1812, doi:10.3762/bjoc.14.153

• evolution Using the as-prepared g-C3N4, CO2 reduction was conducted with the aid of RuP cocatalyst and Ag promoter in a N,N-dimethylacetamide (DMA)/TEOA mixed solution under visible light (λ > 400 nm). Here TEOA works as an effective electron donor that scavenges holes generated in the valence band of g

• in this study. Ag nanoparticles loaded on mpg-C3N4 serves as a promoter of electron transfer from mpg-C3N4 to RuP, as discussed in our previous work [13]. TEM observation indicated that the loaded Ag is in the form of nanoparticles of 5–10 nm in size (Figure 5). Without Ag (i.e., RuP/g-C3N4), formate

• production was clearly observable, but the activity was typically 20% that of RuP/Ag/g-C3N4. Hence we employed Ag as an additional promoter in all cases. It should be also noted that no reaction took place using only g-C3N4. As listed in Table 2, the main product during the reaction was formate with 90–95

Natural and redesigned wasp venom peptides with selective antitumoral activity

• Marcelo D. T. Torres,
• Gislaine P. Andrade,
• Roseli H. Sato,
• Cibele N. Pedron,
• Tania M. Manieri,
• Giselle Cerchiaro,
• Anderson O. Ribeiro,
• Cesar de la Fuente-Nunez and
• Vani X. Oliveira Jr.

Beilstein J. Org. Chem. 2018, 14, 1693–1703, doi:10.3762/bjoc.14.144

• ). [Phe]6-Des[Thr]11-Dec-NH2 did not present helical tendencies, as analyzed by Torres et al. [10], and was not as hemolytic as the other Phe-substituted analogs (Table 1). [Pro]4-Dec-NH2 was described as an unstructured peptide even in helical promoter media [34][35] by Torres et al. [10] and was

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• . Besides the ability of the catalysts to promote the epoxide ring opening with sulfur nucleophiles at room temperature, the attractiveness of the promoter was its capability to effect opening of the epoxide ring with alcohols, selenols and amines to provide the corresponding β-hydroxy analogs. 3.1.1.2

• yield and high regioselectivity. As an alternative to Lewis acids, Cossy and co-workers reported the use of LiNTf2 promoter for the thiolysis of epoxides [29]. The reaction provided better yields under solvent-free conditions than using dichloromethane as a solvent. Although a wide variety of epoxides

• , the added advantage of the protocol is that when LiNTf2 is used instead of Lewis acids, the work-up is easier as no vexatious emulsion was formed. However, the need for 0.5 equiv of the promoter and the sluggishness (20 h) of the reaction make the method less favorable when compared to other Lewis

Glycosylation reactions mediated by hypervalent iodine: application to the synthesis of nucleosides and carbohydrates

• Yuichi Yoshimura,
• Hideaki Wakamatsu,
• Yoshihiro Natori,
• Yukako Saito and
• Noriaki Minakawa

Beilstein J. Org. Chem. 2018, 14, 1595–1618, doi:10.3762/bjoc.14.137

• disaccharide 158 in good yield (Scheme 20). Randolph and Danishefsky reported a glycal assembly strategy to the synthesis of a branched oligosaccharide [82]. Bennett and co-workers reported that phenyl(trifluoroethyl)iodonium triflimide was a stable promoter for glycosylation reactions using thioglycoside

• /acetonitrile/isobutyronitrile/pivalonitrile greatly improved both the chemical yields and stereoselectivity, as shown in Scheme 21. The results suggested that both the solvent system and iodonium salt promoter are required for selectivity. Even though glycals have a π-electron-rich enol ether unit, reports

Synthetic avenues towards a tetrasaccharide related to Streptococcus pneumonia of serotype 6A

• Aritra Chaudhury,
• Mana Mohan Mukherjee and
• Rina Ghosh

Beilstein J. Org. Chem. 2018, 14, 1095–1102, doi:10.3762/bjoc.14.95

• from NMR). We presume that this near exclusivity in α-selection may be due to the synergistic effect from the 4,6-O-benzylidene group, which is a good promoter for 1,2-cis glycosylation in galactose-based systems [38], as well as the steric crowding caused by the bulky 3-O-naphthylmethyl group at the β

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• ]. Gottesfeld et al. synthesized a series of Py/Im HP-polyamide–DNA alkylator (chlorambucil) (HP-Chl) conjugates in order to bind and alkylate within the HIV-1 promoter region, thereby blocking HIV-1 replication and screened them against human colon carcinoma cell lines [74][75]. It has been observed that

• site in the H4c promoter in treated cells, thereby inhibiting tumor growth in mice. Chenoweth and Dervan showed DNA structural distortion induced by an 8-ring cyclic Py/Im polyamide (conjugate 17) bound to the central 6 bp of the sequence d(5'-CCAGGCCTGG-3')2 by using a high resolution X-ray crystal

• structure as shown in Figure 7a [76]. This allosteric perturbation of the DNA helix by small molecules through binding at distinct locations on promoter DNA provides a clear understanding of how transcription factor activity could be disrupted and gene expressions could also be regulated. In order to target

Palladium-catalyzed ortho-halogenations of acetanilides with N-halosuccinimides via direct sp² C–H bond activation in ball mills

• Zi Liu,
• Hui Xu and
• Guan-Wu Wang

Beilstein J. Org. Chem. 2018, 14, 430–435, doi:10.3762/bjoc.14.31

• reaction of 1a with NIS in the absence of Pd(OAc)2, yet still with PTSA as the promoter, and no iodinated product was furnished (Table 1, entry 3). The use of D-camphorsulfonic acid (D-CSA) or mesitylenesulfonic acid dihydrate provided inferior results than that obtained in the presence of PTSA (Table 1