Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• of a highly active carbocation Lewis acid catalyst. The stereocontrol potential of the chiral tritylium ion pair was demonstrated by its application in an enantioselective Diels–Alder reaction of anthracene. Keywords: anthracene; carbocation catalysis; Diels–Alder reaction; Fe(III)-based phosphate

• , the enantioselectivity was low in most cases. In addition, the synthetic efforts to access these chiral cations were generally non-trivial which limited their further development. Recently, we developed a chiral ion-pair strategy for asymmetric carbocation catalysis, with chiral trityl phosphate as

• (Scheme 1b). In our further explorations, we noticed that the dissociation of trityl phosphate was generally sluggish, thus limiting its applicability. To expand its utility, we report herein a metal-complexed phosphate anion for chiral carbocation catalysis. Weakly coordinating anions [22][23] have been

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• tolerated, giving a comparable yield as the "standard conditions" (Table 1, entry 8). While changing the inorganic base to potassium phosphate tribasic or potassium carbonate gave yields below 75%, we found that cesium carbonate provided a net increase in the yield of the reaction (Table 1, entry 9

Electrophilic oligodeoxynucleotide synthesis using dM-Dmoc for amino protection

• Shahien Shahsavari,
• Dhananjani N. A. M. Eriyagama,
• Bhaskar Halami,
• Vagarshak Begoyan,
• Marina Tanasova,
• Jinsen Chen and
• Shiyue Fang

Beilstein J. Org. Chem. 2019, 15, 1116–1128, doi:10.3762/bjoc.15.108

• removed with an acid in each synthetic cycle. The exo-amino groups of nucleosides dA, dC and dG are protected with acyl groups, the nascent ODN is anchored to a solid support via a base- or nucleophile-cleavable linker, and in the most widely used phosphoramidite technology the phosphate groups are

• temperature briefly. This removed the β-cyanoethyl phosphate protecting groups to give 32. HPLC analysis of the DBU solution did not found any ODN that was cleaved prematurely – an observation consistent with the slow rate of cleavage of succinyl-anchored ODNs from solid support under similar conditions [50

• equal portions. One portion was gently shaken in a solution of DBU/CH3CN (1:9, v/v, 1 mL) at rt for 15 min. The supernatant was removed with a pipette, and the CPG was washed with CH3CN (1 mL × 5). This removed the 2-cyanoethyl groups on the phosphate groups. To the CPG, aqueous NaIO4 (0.4 M, 1 mL) was

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

• Robert J. Kempton,
• Taylor A. Kidd-Kautz,
• Soizic Laurenceau and
• Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

• , followed by addition of bromide 5a, potassium phosphate and PdCl2(dppf)2 in DMF at 85 °C for 3.5 h gave the coupled product 10 in 47–63% yields (Scheme 3). In contrast to the case of the Heck coupling products (6 and 8, Scheme 2), nitrile 10 underwent facile reduction with lithium aluminium hydride. The

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• , bearing one or two N-acetyl glucosamine moieties are capable to bind strongly to the lectin WGA. Experimental Materials and methods Myristoyl chloride was from TCI-Europe (Antwerp, Belgium) and used without further purification. 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphate (POPC) was from Avanti Polar

• color was developed using OPD (100 μL per well, 0.4 mg mL−1 in 0.05 M phosphate-citrate buffer) and urea hydrogen peroxide (0.4 mg mL−1). The reaction was stopped after 10 min by adding H2SO4 (30% v/v, 50 μL per well) and the absorbance was measured at 490 nm. The percentage of inhibition was determined

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• performed in DMSO and depending on their solubility in phosphate buffer + 0.1% DMSO (16a–d) by UV–vis absorption spectroscopy. The compounds were dissolved at 50 µM in the respective solvent and irradiated with the indicated wavelengths to generate a substantial amount of their cis-isomer. This process can

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• , d: R = isopropyl, e: R = CH2CF3. Proposed acetal hydrolysis pathways. Half-lives of 5’-acetal (4a–e) and 3’-acetal-protected (7a,c–e) 2’-deoxythymidines, and 2’-deoxy-3’-O-propen-2-ylthymidine (8b) in acetate (pH 4.94), citrate (pH 5.61) and phosphate (pH 6.82) buffers at 25.0 °C. The ionic strength

Cyclopropene derivatives of aminosugars for metabolic glycoengineering

• Jessica Hassenrück and
• Valentin Wittmann

Beilstein J. Org. Chem. 2019, 15, 584–601, doi:10.3762/bjoc.15.54

• reaction: In a polypropylene vial, the sugar derivatives ManNCp(H2), ManNCyc(H2) and ManNCyoc(H2), respectively, were dissolved in phosphate buffer (100 mM, pH 7.16) to a final concentration of 0.1 M. Sodium pyruvate (15 equiv.) and sialic acid aldolase (a spatula tip) were added. After stirring for 17

Back to the future: Why we need enzymology to build a synthetic metabolism of the future

• Tobias J. Erb

Beilstein J. Org. Chem. 2019, 15, 551–557, doi:10.3762/bjoc.15.49

• into the three-carbon compound dihydroxyacetone phosphate [24]. In addition to that, several alternative photorespiration, methanol assimilation, as well as glycolytic pathways of levels 3 and 4 were developed that are supposedly more carbon and energy efficient compared to their naturally evolved

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• were replaced with 500 μL of cell culture medium containing the compound, and then further cultured for an additional 1 h. Those cells were washed twice with 1× PBS and fixed to the membrane using 4% paraformaldehyde in 5.0 mM sodium phosphate buffer (pH 7.4; 1.0 mL) for 10 min. The fluorescence images

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• = 205 nM), affording ArM 2 (Scheme 13). From the different organometallic moieties tested, the catalyst containing 2,6-diisopropylphenyl groups on the NHC ligand afforded the highest activity for the aqueous RCM of N,N-diallyltosylamine (21). Metathase ArM 2 performed best in phosphate buffer at pH 5.0

• undergo Ru-promoted RCM and CM when the G-III catalyst is used under heterogeneous conditions (water/tert-butanol 3:2) with a large excess of Mg2+. Also in this case, the role of Mg2+ is to protect the oligonucleotide from Ru-induced decomposition by binding to the phosphate backbone. Table 12 summarizes

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• enzymatic synthesis of NR+ from α-D-ribose-1-phosphate and Nam by catalysis with purine nucleoside phosphorylase and sucrose phosphorylase is described in a US patent application by Velasquez et al. [46]. In the NMR experiments, the authors demonstrated the preparation of NR+ but did not isolate pure NR+. 3

• , tripivalate, 5-O-myristolate analogues [34], 2′,3′-O-isopropylidene-1,4-dihydronicotinamide riboside [60], and 1,4-dihydronicotinate ribosides [70]. Typically, the reduction with Na2S2O4 is performed under mild basic conditions (e.g., in a medium of aqueous sodium bicarbonate or potassium phosphate dibasic

• is most commonly modified to generate the phosphorylated derivative of NR+, nicotinamide mononucleotide, NMN. The phosphorylation is achieved by reacting NR+ in its salt form with phosphorus oxychloride in trimethyl phosphate resulting, after hydrolysis, in NMN (Scheme 17). Lee et al. [27] carefully

Chemical structure of cichorinotoxin, a cyclic lipodepsipeptide that is produced by Pseudomonas cichorii and causes varnish spots on lettuce

• Hidekazu Komatsu,
• Takashi Shirakawa,
• Takeo Uchiyama and
• Tsutomu Hoshino

Beilstein J. Org. Chem. 2019, 15, 299–309, doi:10.3762/bjoc.15.27

• HPLC with a C18 column using a solvent system composed of CH3CN and triethylamine phosphate (pH 3.0, see Figures S5B–S5E, Supporting Information File 1). Marfey’s method revealed the presence of 2,4-diaminobutanoic acid (Dab) and Ile in the toxin (Figures S5B and S5D). Four diastereomers are present in

• heated at 35 °C for 1 h, then 2 N aq HCl was added to quench the reaction, and then it was concentrated to dryness. The residues were dissolved in DMSO and subjected to reversed-phase HPLC (C18) using a mobile phase composed of 13% CH3CN/87% 50 mM triethylamine phosphate. Amino acid compositions of

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• as the 6’F-bc4,3-DNA. Furthermore, duplexes of a 6’F-bc4,3-modified strand paired to RNA unveiled in the MD simulations a flexible minor groove distance [37]. This flexibility is thought to play a crucial role for the fitting of the duplex into the DNA-binding channel and the phosphate-binding pocket

• of the enzyme. Furthermore, the phosphate-binding pocket requires a large distortion of the backbone angle α in order that the phosphate group of the AON can be positioned in it [50][51]. The 6’F-bc4,3-DNA containing strand also complied with this requirement according to the MD simulations [37

Asymmetric synthesis of a high added value chiral amine using immobilized ω-transaminases

• Antonella Petri,
• Valeria Colonna and
• Oreste Piccolo

Beilstein J. Org. Chem. 2019, 15, 60–66, doi:10.3762/bjoc.15.6

• prochiral precursor 1-Boc-3-piperidone using immobilized ω-transaminases (TAs-IMB), isopropylamine as amine donor and pyridoxal-5’-phosphate (PLP) as cofactor is described. Compared to other methods, the present approach affords the target compound in just one step with high yield and high enantiomeric

• more sustainable method for chiral amine production [2][3][4][5]. TAs, also known as aminotransferases, are enzymes capable of transferring an amino group from an amine donor to an acceptor containing a carbonyl functionality in the presence of pyridoxal-5'-phosphate (PLP) as a cofactor and the enzymes

Lectins of Mycobacterium tuberculosis – rarely studied proteins

• Katharina Kolbe,
• Sri Kumar Veleti,
• Norbert Reiling and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2019, 15, 1–15, doi:10.3762/bjoc.15.1

• the fast growing non-pathogenic species Mycobacterium smegmatis (M. smegmatis) contains inositol phosphate-capped LAM (PILAM) [54]. In addition to lipoglycans, various free, noncovalently associated glycolipids are present in the mycobacterial cell wall, such as the mycolic acid diester trehalose 6,6

Impact of Pseudomonas aeruginosa quorum sensing signaling molecules on adhesion and inflammatory markers in endothelial cells

• Carmen Curutiu,
• Florin Iordache,
• Veronica Lazar,
• Aurelia Magdalena Pisoschi,
• Aneta Pop,
• Mariana Carmen Chifiriuc and
• Alina Maria Hoban

Beilstein J. Org. Chem. 2018, 14, 2580–2588, doi:10.3762/bjoc.14.235

• containing Tryptic Soy Broth (TSB) for 24 h, 48 h and 72 h at 37 °C. After each period of time, the plates were subsequently emptied and washed three times with phosphate buffered saline (PBS). The adherent cells were then fixed with cold methanol, stained with an alkaline 1% crystal violet solution for 15

• were washed with PBS (phosphate buffered saline) and 1 mL of fresh medium without antibiotics was added to each well. Suspensions of P. aeruginosa were obtained from bacterial mid-logarithmic phase cultures grown in nutrient broth adjusted to 107 CFU/mL and 1 mL were used for the inoculation of each

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• , compound 50 was treated with KHMDS in THF at −78 °C to produce enolate 51. Further, it was reacted with diphenyl chlorophosphate to generate vinyl phosphate 52, which was subjected to SM coupling in the presence of different 2-formylboronic acids 53 with the aid of the Pd(PPh3)4 catalyst to provide the

Synthesis of a water-soluble 2,2′-biphen[4]arene and its efficient complexation and sensitive fluorescence enhancement towards palmatine and berberine

• Xiayang Huang,
• Xinghua Zhang,
• Tianxin Qian,
• Junwei Ma,
• Lei Cui and
• Chunju Li

Beilstein J. Org. Chem. 2018, 14, 2236–2241, doi:10.3762/bjoc.14.198

• 1H NMR spectroscopy in aqueous phosphate buffer solution (pH 7.4). In the presence of 2,2’-CBP4, 1H NMR signals of P and B displayed very large upfield shifts, indicating the formation of inclusion complexes with strong binding affinities. Fluorescence titration experiments showed that P and B

• experiments of P and B with 2,2’-CBP4 in deuterated phosphate buffer (pD 7.4) were carried out to examine the host–guest complexation (Figure 1 and Figure S9 in Supporting Information File 1). From Figure 1, upon addition of the host, all the peaks of alkaloid B displayed upfield shifts and broadening

• ). To examine the fluorecence behavior and to quantitatively assess the complexation of the two alkaloids and 2,2’-CBP4, spectral titrations of P/B and 2,2’-CBP4 were performed in the phosphate buffer solution of pH 7.4 at 298 K. As can be seen from Figure 2 and Supporting Information File 1, Figure S10

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• (Figure 3). In a previous work, our DLS studies of this host involved solutions buffered with 40 mM phosphate (pH 7.3) [14]. Under these conditions, the initially measured sizes in the absence of added salt were consistently 1.9–2.1 nm; values that match the modeling of the host. In stark contrast to this

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• seen ADP more effectively embeds into the molecular cleft formed by two ammonium moieties due to a good host–guest geometric size and/or shape complementarity (Figure 4a and c). The three phosphate groups of ATP have a larger size and cannot realize a similar supramolecular motif in the complex. For

• (12b) = 2 µM, concentration (adenosine phosphate) = 2 mM, concentration (MES) = 50 mM (pH 6.5). Supramolecular binding motif of diphosphate (a) and triphosphate (b) groups of nucleotides with the protonated diethylenetriamine substituents of the calixarene (ribose and adenine fragments are omitted for

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• phosphate buffer (95 mM K+; 5% DMSO; pH 7.0); cL = 20.0 μM. Arrows indicate the development of bands with increasing DNA concentration. Inset: Plot of the absorption at long wavelength versus DNA concentration. Fluorimetric titration of 2a (A), 2b (B) and 2d (C) with ct DNA in potassium phosphate buffer (95

• 380 nm (C). Fluorimetric titration of 2a (A) and 2d (B) with 22AG in potassium phosphate buffer (95 mM K+; 5% DMSO; pH 7.0); cLigand = 20.0 μM. Arrows indicate the development of the bands with increasing DNA concentration. Inset: Plot of the relative emission intensity, I/I0 versus cDNA/cL. Lines

Strong binding and fluorescence sensing of bisphosphonates by guanidinium-modified calix[5]arene

• Jie Gao,
• Zhe Zheng,
• Lin Shi,
• Si-Qi Wu,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2018, 14, 1840–1845, doi:10.3762/bjoc.14.157

• ]arene (GC5A, Scheme 1b). Such label-free sensing strategy exhibits potential application in real-time monitoring concentrations of BPs in urine and pharmacokinetic studies. Results and Discussion The main skeleton of BPs possesses two phosphate groups which are potential binding sites and therefore GC5A

• was tested as binding receptor. GC5A was prepared according to our previous procedure [26] and the guanidinium groups installed in the upper rim are expected to form multiple salt bridge interactions (charge-assisted hydrogen bonds) with the phosphate groups of BPs (Scheme 1c) [26][29]. To execute IDA

• etidronate in (a) HEPES buffer (10 mM, pH 7.4) and (b) artificial urine at 25 °C. Error bars could not be shown if less than 0.005. The chemical structures of (a) bisphosphonates (BPs) and (b) guanidinium-modified calix[5]arene (GC5A). (c) Schematic illustration of a salt-bridge between a phosphate anion and

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

• ranged from –78 °C to room temperature. The use of amines, alcohols as well as alkyl and arylthiols as nucleophiles failed to provide the corresponding products. A year later, Antilla and co-workers found lithium-binol phosphate 64 to be an efficient catalyst for the desymmetrization of meso-epoxides

• complex. Enantioselective ring-opening reaction of stilbene oxides with ArSH catalyzed by a C2-symmetric chiral bipyridyldiol–titanium complex. Asymmetric desymmetrization of meso-epoxides using BINOL-based Brønsted acid catalysts. Lithium-BINOL-phosphate-catalyzed desymmetrization of meso-epoxides with

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• -mannopyranose (3) as a 9:1 α,β-mixture in order to optimize the reaction conditions for the Mitsunobu reaction with phosphoric acid dibenzyl ester. The anomeric mannosyl phosphate derivatives 39α and 39β were obtained in 57% total yield when pyridine was used as the solvent, as depicted in Scheme 7. In THF, the

• trimethylamine in dichloromethane improved the Mitsunobu process, leading to 40α and 40β in more than 70% yield. When such optimized conditions were applied to the mannose-6-phosphate derivative 41, the desired bisphosphate 42 was obtained in 56% yield as a 40:60 α,β-anomeric mixture before work-up, and in a 53