Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• , such as camphorsulfonic acid (CSA) [44], diammonium hydrogen phosphate (DAHP) [45], Amberlyst 15 [46], P2O5/MeSO3H [47], p-sulfonic acid calix[4]arene [48], xanthan sulfuric acid (XSA) [49], H5PW10V2O40/pyridino-santa barbara amorphous-15 (SBA-15) [50], TiO2-SO42− [51][52], humic acid [53] or Lewis

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• the chiral phosphate co-catalyst (Scheme 5B). This event leads to the generation of a potent IrII reductant that begins the photocatalytic cycle by reducing 16 into radical anion 17 while regenerating the ground state of the IrIII photocatalyst. After fragmentation, α-amino radical 18 was proposed to

• undergo addition to the heterocyclic radical acceptor 19 through a ternary transition state 20 involving hydrogen bonding interactions with the chiral phosphate co-catalyst. Notably, a follow-up report revealed that the radical addition is reversible, and that the selectivity determining step involves the

• -coupled electron transfer (PCET), forming neutral radical species 33 and the corresponding phosphate conjugate base (Scheme 8B). The hypothesis is supported by an observed increase in the luminescence quenching of *Ir(p-CF3-ppy)3 by 32 in the presence of diphenyl phosphoric acid, as quantified by the

Elucidating the glycan-binding specificity and structure of Cucumis melo agglutinin, a new R-type lectin

• Jon Lundstrøm,
• Emilie Gillon,
• Valérie Chazalet,
• Nicole Kerekes,
• Antonio Di Maio,
• Ten Feizi,
• Yan Liu,
• Annabelle Varrot and
• Daniel Bojar

Beilstein J. Org. Chem. 2024, 20, 306–320, doi:10.3762/bjoc.20.31

• column (GE healthcare) at 5 mL/min. The column was washed with 10 mM phosphate-buffered saline (Medicago), 500 mM NaCl and 50 mM imidazole before elution of the protein using the same buffer with a gradient from 50 mM to 500 mM imidazole (G-Biosciences) over 15 column volumes. Pooled fractions were

• concentrated using Vivaspin concentrators (MWCO 10 kDa, Sartorius Stedim), passed over a HiPrep 26/10 desalting column (GE Healthcare) in phosphate-buffered saline (Medicago), and finally concentrated again. For bacterial expression, the gene of CMA1 (33–291, corresponding to residues 6–291 of the mature

Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process

• Kazuhiro Okamoto,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27

• hydroamination reaction products via a proton-coupled electron transfer (PCET) mechanism. Cyclic voltammetry (CV) analysis indicated that the chemoselectivity was derived from the size of the hydrogen bond complex, which consisted of the carbamate substrate and phosphate base, and could be controlled using

• presence of methyl vinyl ketone (MVK) as a radical acceptor (Table 1). Tetrabutylammonium dibutyl phosphate (phosphate base), which operates as a PCET initiator through hydrogen bond formation with the N–H bond of amide/carbamate [11], was used as an additive. As a result, N-alkylated product 3 was

• exclusively obtained, implying that the expected HAT at the 1’-C position to afford 2 (Table 1, entry 1) had not occurred. In contrast, the reaction efficiency was significantly decreased in the absence of the phosphate base (Table 1, entry 2), and electricity is necessary to proceed the reaction (Table 1

Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• applications due to their improved solubility in aqueous systems. Assembly is achieved by integrating distinct carbohydrate, peptide, and polyprenyl phosphate building blocks. This modular synthetic method allows for the strategic substitution of constituent building blocks at different synthetic stages and

• -phosphite intermediate was then oxidized with hydrogen peroxide to yield dibenzyl α-phosphate 6, achieving an overall yield of 89% for these two steps. Removal of the 2-(phenylsulfonyl)ethanol protecting group in compound 6 was successfully achieved through treatment with 1,8-diazabicyclo[5.4.0]undec-7-ene

• Supporting Information File 1 for comprehensive information on the synthesis details of the tetrapeptide). To avoid loss of valuable material through HPLC purification, crude 7 is used directly in the next step, and purification performed after the final prenyl phosphate coupling and global deprotection

Chiral phosphoric acid-catalyzed transfer hydrogenation of 3,3-difluoro-3H-indoles

• Yumei Wang,
• Guangzhu Wang,
• Yanping Zhu and
• Kaiwu Dong

Beilstein J. Org. Chem. 2024, 20, 205–211, doi:10.3762/bjoc.20.20

• , synthesized in situ from a chiral boron phosphate complex with water, for asymmetric indole reduction (Scheme 1b) [30]. The mild reaction conditions, low catalyst loading, and high enantioselectivity rendered this transformation an attractive approach to synthesize optically active indolines. However, these

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• mixtures were determined to be 78%, 73%, 30%, and 20% in MeCN, >97%, 80%, 44% and 55% in H2O, and 32%, 76%, 53% and 38% in Na phosphate buffer. Overall, the initially formed amounts of photoproducts are significantly larger than the ones of the isolated compounds, in the case of 3c and 3e even with good

• ct DNA were irradiated in phosphate buffer, and the formation of the dimethoxybenzo[c]quinolizinium ions and their subsequent binding to the DNA were shown photometrically by the development of the characteristic red-shifted absorption bands (Figure 7A, cf. Supporting Information File 1, Figure S7A

• : spectrum at the end of the irradiation. Photometric titration of ct DNA to 3c (A) 3e (B) 3f (C) and 3g (D) (c = 20 µM) in Na phosphate buffer (pH 7.0, T = 20 °C, cNa+ = 16 mM). The arrows indicate the development of the absorption bands during titration. Inset: plot of absorption versus cDNA. Fluorimetric

Identification of the p-coumaric acid biosynthetic gene cluster in Kutzneria albida: insights into the diazotization-dependent deamination pathway

• Seiji Kawai,
• Akito Yamada,
• Yohei Katsuyama and
• Yasuo Ohnishi

Beilstein J. Org. Chem. 2024, 20, 1–11, doi:10.3762/bjoc.20.1

• acid through a completely different pathway, which requires at least 12 enzymes and two carrier proteins if two primary metabolites (dihydroxyacetone phosphate and aspartate-4-semialdehyde) are considered as starting materials. Thus, the Cma system appears to be more complicated than the general p

Effects of the aldehyde-derived ring substituent on the properties of two new bioinspired trimethoxybenzoylhydrazones: methyl vs nitro groups

• Dayanne Martins,
• Roberta Lamosa,
• Talis Uelisson da Silva,
• Carolina B. P. Ligiero,
• Sérgio de Paula Machado,
• Daphne S. Cukierman and
• Nicolás A. Rey

Beilstein J. Org. Chem. 2023, 19, 1713–1727, doi:10.3762/bjoc.19.125

• registering the UV–vis spectra of a series of hdz-NO2 10% DMSO/buffer (acetate, phosphate or Tris-HCl) solutions with different pH values, ranging from 3.8 to 8.2 (Figure 7A). By plotting the absorbance at λmax as a function of pH and then fitting the curve with a sigmoidal function (Figure 7A, inset), an

Cyclodextrins permeabilize DPPC liposome membranes: a focus on cholesterol content, cyclodextrin type, and concentration

• Ghenwa Nasr,
• Hélène Greige-Gerges,
• Sophie Fourmentin,
• Abdelhamid Elaissari and
• Nathalie Khreich

Beilstein J. Org. Chem. 2023, 19, 1570–1579, doi:10.3762/bjoc.19.115

• . Triton X-100, sodium chloride (NaCl), and Sephadex G25 gel were purchased from Sigma-Aldrich, Belgium. Ammonium molybdate, hydrogen peroxide, potassium dihydrogen phosphate, sodium sulfite, sodium bisulfite, chloroform, and methanol were purchased from Sigma-Aldrich, Germany. Cholesterol and

Synthesis of ether lipids: natural compounds and analogues

• Marco Antônio G. B. Gomes,
• Alicia Bauduin,
• Chloé Le Roux,
• Romain Fouinneteau,
• Wilfried Berthe,
• Mathieu Berchel,
• Hélène Couthon and
• Paul-Alain Jaffrès

Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96

• correspond, for instance, to biosynthesized intermediates (e.g., 1-O-alkyl-glycerol-3-phosphate [4], lyso-PAF [5]) or neutral ether lipids (e.g., diacyl ether glycerol [6]). Ether glycerolipids are present in mammalian but also in anaerobic bacteria [7], archea (with an inverted stereochemistry at the sn-2

• of the secondary alcohol produced 2.3. The primary alcohol was deprotected in acidic conditions to produce 2.4. The installation of the phosphocholine polar head group was achieved in two steps starting with the reaction of 2.4 with bromoethyl dichlorophosphate (2.5) to produce the phosphate

• oxidation with Br2 and hydrolysis, the bromoethyl phosphate 5.4. Finally, the quaternarization with trimethylamine produced 5.5 and the acetylation produced 5.6 PAF. The intermediate compounds like 6.2 (1-O-alkylglycerol) or the protected secondary alcohol 6.6, either as enantiopure or racemic forms, are

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• tris buffer rather than phosphate [44]. Instead of using the regenerated NADH in a photocatalytic system, this team actually used an enzyme to consume the regenerated NADH and check its viability. Robert and co-workers recycled the NADH analogue 1,4-BNAH using different photosensitizers and cobalt

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

CO₂ complexation with cyclodextrins

• Cecilie Høgfeldt Jessen,
• Jesper Bendix,
• Theis Brock Nannestad,
• Heloisa Bordallo,
• Martin Jæger Pedersen,
• Christian Marcus Pedersen and
• Mikael Bols

Beilstein J. Org. Chem. 2023, 19, 1021–1027, doi:10.3762/bjoc.19.78

• coverage of the bottom. The analysis shown in Figure 3 was started at 28 °C, and was finished at a temperature of 150 °C with a heating rate of 5 °C/min. Determination of dissociation constants between 7 and CD’s. Samples were prepared that consisted of citrate-phosphate buffer (pH 3, 50 mM), 7 (40 μM) and

• association constants between CD’s and CO2. Samples were prepared that consisted of citrate-phosphate buffer (pH 3, 50 mM), 7 (40 μM) and a fixed concentration of cyclodextrin ([CD]o; 1–4 mM) and put into the pressure cell. The spectrum was recorded at 0, 2, 4 , 6 and/or 8 bar CO2 pressure over the liquid

• pressure autoclave. [CD]tot is the starting concentration of cyclodextrin. [CD·CO2]/[CD]tot is the calculated ratio of bound CO2 in solution using a Kg of 0.18 bar−1. Kd for binding of 7 and Ka for binding CO2 for cyclodextrin derivatives in citrate-phosphate buffer at pH 3. Crystal data and structure

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• dehydration to generate isoxazolium cation 80 paired with a phosphate anion. This chiral phosphate is engaged in H-bonding with the free NH of the heteroarene ring to ease the stereoselective 1,2-addition to in situ generate the cationic heterocyclic scaffold 81. The reaction proceeded faster with pyrroles

• Brønsted acid to generate (N-acyl)(propargyl)imine 90 as intermediate which added to the deprotonated phosphoric acid to form phosphate ester 91 as the next intermediate through an equilibrium process. Then, 1,2-addition by the C3 position of the heteroarene ring to the acylimine intermediate afforded the

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• according to experimental literature with slight modification [20]. α-Glucosidase (0.05 U/mL) and substrate, p-nitrophenyl-α-ᴅ-glucopyronoside (p-NPG) (1 mM) were dissolved in 0.1 M sodium phosphate buffer (pH 6.9). Fifty μL of sample (1 mg/mL in 10% DMSO) and 50 μL of α-glucosidase were preincubated at 37

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• response concerning the excimer band was obtained independently on polynucleotide’s structure and/or base composition. Fluorescence quenching upon binding was similar to the previously published bispyrene–guanidiniocarbonyl compound, which was found to bind along the phosphate backbone of most of examined

Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups

• Ita Hajdin,
• Romana Pajkert,
• Mira Keßler,
• Jianlin Han,
• Haibo Mei and
• Gerd-Volker Röschenthaler

Beilstein J. Org. Chem. 2023, 19, 541–549, doi:10.3762/bjoc.19.39

• or by photolysis of pyrazolines bearing difluoromethylphosphonate moieties (Scheme 1C) [35][36][37][38]. Notably, among the various CF2-containing functionalities, difluoromethylphosphonates represent a distinct class of compounds whose potential as nonhydrolyzable phosphate mimics is unquestionable

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• for catalytic ester reduction with H2 [48], led to lower catalyst activity. Possible coordination of residual phosphate to the guanidine moiety was excluded as analysis by 31P NMR experiments. The copper(I)-catalyzed 1,2-reduction of functionalized ester 10 was also successfully achieved using the

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• to improve the water solubility of combretastatin D-2 (2) by converting it into a series of phosphate salts and other prodrugs. Thus, phosphorylation of combretastatin D-2 (2) using dibenzyl phosphite gave derivative 183. Further cleavage of the benzyl groups using TMSBr followed by the reaction of

• the obtained phosphoric acid derivative with a series of bases led to the formation of different phosphate salts 184–187 (Scheme 35) [55]. The authors observed that the prodrug salts had substantially improved solubility in water, an important feature for transport to metastatic cancer (Table 3) [75

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• -triazol-4-yl)methyl]amine, MW, 70 °C (iii) LiOH, water, room temperature, 3 h (iv) phosphate buffer pH 7, [Re(CO)3Br3][NEt4]2, 65 °C, 2 h (v) [99mTc(CO)3(H2O)3]+, pH 7.4, 90 °C, 30 min. Synthesis of meso-triazole-bridged porphyrin-quinolone conjugates 70a–e. Synthesis of meso-triazole-linked porphyrin

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• achieved. When AgOTf was replaced with silver (R)-BINOL phosphate, the asymmetric allylation proceeded in a moderate yield (60%) and enantioselectivity (40% ee). The structure of the ‘GaIOTf’ species was explored in more detail by Slattery, and a monovalent [GaI(18-crown-6)OTf] complex was isolated and

Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements

• Robert N. Goldberg,
• Robert T. Giessmann,
• Peter J. Halling,
• Carsten Kettner and
• Hans V. Westerhoff

Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26

• biochemical reaction and the many chemical reactions that accompany it is the hydrolysis reaction of ATP (adenosine 5’-triphosphate) to {ADP (adenosine 5’-diphosphate) + phosphate}: The apparent reaction quotient for this reaction is And the apparent equilibrium constant is Here, (aq) denotes that the

• reaction is taking place in aqueous media and c denotes the respective concentrations (units of mol∙dm−3) of total amounts of ATP, ADP, and phosphate. Note that Q′ and K′ have the same form but they differ critically in that a measured value of K′ refers to Equation 1 having been established to be at

• be written for total ADP and total phosphate. The word “total” is sometimes used to specify total concentrations and, while useful, it seems cumbersome and unnecessary if the context is clear. A substantial number of chemical reference reactions can be selected for the biochemical Equation 1 – a few

An accelerated Rauhut–Currier dimerization enabled the synthesis of (±)-incarvilleatone and anticancer studies

• Tharun K. Kotammagari,
• Sweta Misra,
• Sayantan Paul,
• Sunita Kunte,
• Rajesh G. Gonnade,
• Manas K. Santra and
• Asish K. Bhattacharya

Beilstein J. Org. Chem. 2023, 19, 204–211, doi:10.3762/bjoc.19.19

• a growth suppression. Colorimetric MTT assays are widely used to examine a growth suppression. In these assays, viable cells reduce MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) to its insoluble formazan by oxidoreductase enzymes in a nicotinamide adenine dinucleotide phosphate

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• , the presence of NMP is actually detrimental. Indeed, for the cross coupling reaction of octylmagnesium chloride with 1-butadienyl phosphate in THF at −20°C in the presence of 1% Fe(acac)3 and 9 equivalents of NMP, the resulting 1,3-dodecadiene cross-coupling product was only obtained with a 54% yield

• and NHCs was also described by Duong for the aryl–aryl cross coupling [29]. Alkoxide salts appear as good alternatives to NMP or phosphate-based additives, since several classic alcohol sources display low toxicities and can also come from renewable resources [30]. In this context, Cahiez and Lefèvre

• nucleophilic partners and as a magnesium alkoxide additive source, enabling the development of iron-mediated cross-coupling procedures with alkenyl or dienyl halides, requiring neither heavy alkyl phosphate leaving groups nor toxic solvents such as NMP. Moreover, those procedures can be carried out at large