Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• membrane-based liquid–liquid separators the ability to gradually adjust the pH of the crude material stands out as an option to enable continuous purification. Though this approach does not apply to all substrates, it allows for tuning of parameters and sequential removal of impurities. Thorough

• [52]. After three sequential liquid–liquid extractions and a passage through a scavenger resin, atropine was obtained in >98% purity, after solvent evaporation as the only off-line operation. This was achieved due to careful pH control that enabled the separation of all byproducts, some of which

• having very similar structures. To purify a mixture by tuning its pH, the target compound must be ionizable. Recently, Blacker and co-workers developed an autonomous system for screening liquid–liquid extraction conditions using a Zaiput membrane [53]. The system is monitored by both online and inline

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• alcohol on the A ring in 75% yield. The C3 epimer was also obtained in 4% yield and confirmed by X-ray diffraction. Hydrogenation of the sterically hindered C1–C2 alkene was accomplished using a combination of Mn(dpm)3 and Ph(iPrO)SiH2, providing grayanotoxin III in 51% yield. The authors also achieved

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• transfer between the C-centered radical and (SPyf)2, whereas for Me-, CF3-, Ph-, and C6F5-derived thiols and disulfides HAT is more favorable than thiyl group transfer [123]. Quinone catalysis Quinones are well known as redox-active cofactors in biochemical processes and have found wide synthetic

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• hydrolysis of compounds 8 and 9 to form the corresponding amino acids. Thus, treating bicycle 8 with aqueous lithium hydroxide resulted in hydrolysis of the ethyl ester, and subsequent neutralization with pH 7 phosphate buffer afforded halichonic acid ((−)-1) in 88% yield after purification by column

• oxocarbenium ion 16. Subsequent loss of the ethyl group (either as ethyl formate upon solvolysis with the formic acid co-solvent or as ethanol upon aqueous workup) gives lactone 9, which features a strained trans-fused 6/5 ring system. Although this lactone survives aqueous workup at neutral pH, it is rapidly

One-pot double annulations to confer diastereoselective spirooxindolepyrrolothiazoles

• Juan Lu,
• Bin Yao,
• Desheng Zhan,
• Zhuo Sun,
• Yun Ji and
• Xiaofeng Zhang

Beilstein J. Org. Chem. 2022, 18, 1607–1616, doi:10.3762/bjoc.18.171

• different R1 was employed for the synthesis to give 7f with COMe in a trace amount and no product 7g with a Ph group. The following reactions with aliphatic aldehydes gave 7h and 7i as complex mixtures [54][55][56][57][58][59][71]. The reaction mechanism of the double annulations for sequential N,S

Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene

• Konstantin Lebedinskiy,
• Volodymyr Lobaz and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170

• adding any solvent. The DIPEA can be effectively replaced by another relatively weak organic base, such as TEA, TBA, or 2,6-lutidine. The reaction proceeds at 100 °C and is usually finished in 10–12 hours, yielding compound 8. However, it demands a steady pH control because the basicity of the reaction

Solid-phase total synthesis and structural confirmation of antimicrobial longicatenamide A

• Takumi Matsumoto,
• Takefumi Kuranaga,
• Yuto Taniguchi,
• Weicheng Wang and
• Hideaki Kakeya

Beilstein J. Org. Chem. 2022, 18, 1560–1566, doi:10.3762/bjoc.18.166

• ][27][28][29], such as concentration, pH, and purity. Thus, analyses of the NMR spectra of peptides sometimes lead to incorrect structural determination even though total synthesis of the proposed structures is successful [30]. In this study, synthesized and natural 1 were compared by collecting LC–MS

Comparison of crystal structure and DFT calculations of triferrocenyl trithiophosphite’s conformance

• Ruslan P. Shekurov,
• Mikhail N. Khrizanforov,
• Ilya A. Bezkishko,
• Tatiana P. Gerasimova,
• Almaz A. Zagidullin,
• Daut R. Islamov and
• Vasili A. Miluykov

Beilstein J. Org. Chem. 2022, 18, 1499–1504, doi:10.3762/bjoc.18.157

• interactions differ noticeably from each other. At the same time one should underline the role of the ferrocene moiety for the crystal structure of the (FcS)3P. The related (PhS)3P molecule with Ph rings instead of Fc units exist in the propeller-like gauche-gauche-gauche configuration [21], forming the C–H

Design, synthesis, and evaluation of chiral thiophosphorus acids as organocatalysts

• Karen R. Winters and
• Jean-Luc Montchamp

Beilstein J. Org. Chem. 2022, 18, 1471–1478, doi:10.3762/bjoc.18.154

• are currently under investigation and results will be shared in due course. Chiral phosphorus acids (CPAs) derived from BINOL, VAPOL, and SPINOL. R = H, Ph, 4-PhC6H4-, 4-β-naphthylphenyl, 9-anthryl, 3,5-dimesitylphenyl, 3,5-diphenylphenyl, 4-MeC6H4-, 4-CF3C6H4-, 4-t-BuC6H4-, β-naphthyl, 3,5-t-Bu2C6H3

Synthesis of the biologically important dideuterium-labelled adenosine triphosphate analogue ApppI(d₂)

• Petri A. Turhanen

Beilstein J. Org. Chem. 2022, 18, 1466–1470, doi:10.3762/bjoc.18.153

• added, and the reaction mixture was stirred at 0–3 °C for 1 h. The reaction mixture was made basic by adding an appropriate volume of 4 M NaOH with stirring (pH value measured by pH paper), and acetone was removed by evaporation in vacuum. The remaining mixture was acidified by addition of 6 M HCl and

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• minimal impacts on the geometry and the 3LE state energy in the dyad, was rarely explored [8]. We also modified the energy of the CT states by increasing the distance between the electron donor and acceptor by using an intervening phenyl linker between the NI and the PTZ moieties (NI-Ph-PTZ and NI-PhMe2

• -PTZ) [36]. The electronic coupling between the NI and PTZ units differ these two dyads. Finally, in NI-PhMe2-PTZ with methyl substituents, the phenyl linker adopts an orthogonal geometry with respect to the NI moiety, inducing a weaker coupling than that in NI-Ph-PTZ. The photophysical properties of

• , confirming that the CT absorption band strongly depends on the electron-donating ability of the donor. In both NI-Ph-PTZ and NI-PhMe2-PTZ, the CT band is negligible, due to the large separation between the NI and PTZ moieties. Note that in NI-Ph-PTZ, the electronic coupling between the NI and the phenyl

Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition

• Anaïs Rousseau,
• Guillaume Vincent and
• Cyrille Kouklovsky

Beilstein J. Org. Chem. 2022, 18, 1385–1395, doi:10.3762/bjoc.18.143

• (981 mg, 2.06 mmol, 2 equiv), calcium carbonate (206 mg, 2.06 mmol, 2 equiv) and water (40 µL, 2.06 mmol, 2 equiv) in isopropanol (1.8 mL). The mixture was stirred at rt for 30 h. Water (0.75 mL) was added and the solution stirred for additional 1 h. The pH was adjusted to 8 by addition of saturated

Cyclodextrin-based Schiff base pro-fragrances: Synthesis and release studies

• Attila Palágyi,
• Jindřich Jindřich,
• Juraj Dian and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2022, 18, 1346–1354, doi:10.3762/bjoc.18.140

• – cinnamaldehyde, cyclamen aldehyde, lilial, benzaldehyde, anisaldehyde, vanillin, hexanal, heptanal, citral, and 5-methylfurfural. Subsequently, the rate of release of the volatile compound from selected pro-fragrances, as a function of the environment (solvent, pH), was studied by 1H NMR spectroscopy (for

• benzaldehyde) and static headspace-gas chromatography (for benzaldehyde, heptanal, and 5-methylfurfural). The aldehyde release rate from the imine was shown to depend substantially on the pH from the solution and the air humidity from the solid state. Keywords: aldehyde; controlled release; cyclodextrin

• industry, the covalent bond that links the fragrance to its substrate must be cleaved under environmental conditions found in everyday life, and the substrate should be non-volatile and non-toxic [17]. Typical triggers that may be used for mild chemical reactions are temperature, enzymatic or pH-dependent

Computational model predicts protein binding sites of a luminescent ligand equipped with guanidiniocarbonyl-pyrrole groups

• Neda Rafieiolhosseini,
• Matthias Killa,
• Thorben Neumann,
• Niklas Tötsch,
• Jean-Noël Grad,
• Alexander Höing,
• Thies Dirksmeyer,
• Jochen Niemeyer,
• Christian Ottmann,
• Shirley K. Knauer,
• Michael Giese,
• Jens Voskuhl and
• Daniel Hoffmann

Beilstein J. Org. Chem. 2022, 18, 1322–1331, doi:10.3762/bjoc.18.137

• ). Additionally, fluorescence- and UV-titration experiments suggested a dissociation constant in the low micromolar range (5.0 ± 0.9 µM/7.5 ± 1.1 µM, respectively) in buffered aqueous solution (25 mM HEPES, 150 mM NaCl, 10 mM MgCl2, 0.5 mM TCEP, pH 6.5) (Supporting Information File 1, Figures S26 and S28

• , [20]) was refined with MODELLER [31] as described in reference [26]. Charges, van der Waals radii and missing hydrogen atoms were added by PDB2PQR v2.0.0 [27][28] at pH 6.5 with the Amber force field option (values are provided as a table in Supporting Information File 2 and in Supporting Information

Make or break: the thermodynamic equilibrium of polyphosphate kinase-catalysed reactions

• Michael Keppler,
• Sandra Moser,
• Henning J. Jessen,
• Christoph Held and
• Jennifer N. Andexer

Beilstein J. Org. Chem. 2022, 18, 1278–1288, doi:10.3762/bjoc.18.134

• [33][34]. Under physiological conditions as well as in an in vitro system the actual ΔG may be different by coordination of cations and the ionic strength, temperature and pH of the reaction solution [29][35][36]. Compared to other ATP synthesis reactions very little is known about the thermodynamics

• between different PPKs [10][15]. First experiments were conducted with the “model PPKs” EcPPK1 and SmPPK2. At 37 °C and pH 8, each enzyme was incubated with either ADP or ATP and polyP as co-substrate; the resulting nucleotide distributions were analysed by HPLC as a function of time (Figure 4). In all

• started with ADP catalysed by a) SmPPK2 and b) EcPPK1. Time courses of reactions started with ATP catalysed by c) SmPPK2 and d) EcPPK1. The nucleotide concentration was 2 mM, the reaction was carried out at pH 8.0 and 37 °C. Grey = AMP, blue = ADP, orange = ATP; the nucleotide composition is given in mol

Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure

• Irene Torres-García,
• Josefa L. López-Martínez,
• Rocío López-Domene,
• Manuel Muñoz-Dorado,
• Ignacio Rodríguez-García and
• Miriam Álvarez-Corral

Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132

• is performed with stoichiometric amounts of CpTiCl3 or if catalytic amounts are used [12]. However, using the particular substrates in this approach, the allenic compound 3 was exclusively formed, in a satisfactory 81% yield [14]. It is also important to control the pH during the reaction workup, as

• some contamination of the product with lactone 5 can arise at low pH values, which goes in detriment of the yield. The 2,5-dihydrofuran ring in target compound 1 was obtained through a Ag(I)-mediated intramolecular addition of the hydroxy to the allene group, a process that transformed allene 3 into

• compound 2. The isopropenyl residue of the target compound 1 was assembled through a two-step sequence. The first one was the addition of an excess of methylmagnesium bromide to the ester 2, that completed the carbon skeleton. The second step was the pH-controlled regioselective dehydration of the tertiary

Lewis acid-catalyzed Pudovik reaction–phospha-Brook rearrangement sequence to access phosphoric esters

• Jin Yang,
• Dang-Wei Qian and
• Shang-Dong Yang

Beilstein J. Org. Chem. 2022, 18, 1188–1194, doi:10.3762/bjoc.18.123

• . However, no clear trend regarding electronic effects could be observed since α-pyridinealdehydes bearing either an electron-donating group (e.g., Me, MeO, Ph) or electron-withdrawing group (e.g., F, Cl, Br, CF3, CO2Me) in position 5 were all well tolerated, and the desired products were generally obtained

A Streptomyces P450 enzyme dimerizes isoflavones from plants

• Run-Zhou Liu,
• Shanchong Chen and
• Lihan Zhang

Beilstein J. Org. Chem. 2022, 18, 1107–1115, doi:10.3762/bjoc.18.113

• General Microbiological Culture Collection Center (CGMCC). Seed culture of this strain was done in ISP-2 medium (yeast extract 0.4 g, malt extract 1 g, glucose 0.4 g, distilled water up to 100 mL, pH 7.2) for 2 days. Isoflavone dimer production was performed on MS agar medium (mannitol 20 g, soy flour 20

• 16 °C and induced with 0.1 mM isopropyl β-ᴅ-1-thiogalactopyranoside (IPTG) for 16 h. Cells were harvested by centrifugation (10 min, 8,000 rpm, 4 °C). For protein purification, cell pellets were resuspended in lysis buffer (50 mM NaH2PO4, 400 mM NaCl, 1 mM TCEP, pH 7.5) and lysed by sonication. After

• removing cell debris by centrifugation, the lysate supernatant was purified by Ni-NTA resin with washing buffer (50 mM NaH2PO4, 150 mM NaCl, 100 mM imidazole, pH 7.5) and elution buffer (50 mM NaH2PO4, 150 mM NaCl, 300 mM imidazole, pH 7.5) and then dialyzed into the storage buffer (50 mM NaH2PO4, 150 mM

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• , 20 mM imidazole, pH 8.0). After ultrasonic cell crushing, the cells were centrifuged at 24,000 rpm for 60 min to remove cell fragments. The supernatant was filtered through 0.22 μm of the filter membrane and then loaded into the nickel column of the rebalanced lysate (HisTraqTM FF, GE Healthcare

• ). The eluent was removed with buffer B (50 mM Tris-HCl, 300 mM NaCl, 250 mM imidazole, pH 8.0) at a flow rate of 2 mL/min, starting from the fourth tube of the collection tube and ending at the sixth tube. The outgoing protein was collected and poured into a precooled filter column (Ultracel series 10

• KDa; GE Healthcare). Then, the collected DatA (or EchA) protein was concentrated and buffer-exchanged into storage buffer (50 mM NaH2PO4, 100 mM NaCl, pH 8.0, containing 10% glycerin). The proteins were tested by SDS-PAGE, frozen using liquid nitrogen, and kept at −80 °C. In vitro reactions DatA

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• was made acidic with 37% hydrochloric acid (3.3 mL, 39.31 mmol), diluted in water (150 mL), and stirred for 15 minutes. A saturated solution of sodium hydrogencarbonate was then slowly added to bring the pH to 6, this was extracted with ethyl acetate (3 × 50 mL) and the organic layer was washed with

• sodium hydrogencarbonate was then slowly added to bring the pH to 6, this was extracted with ethyl acetate (3 × 50 mL) and the organic layer was washed with brine (30 mL), dried over magnesium sulfate, and concentrated to dryness. The residue was purified by a chromatography over silica gel (cyclohexane

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• -azaphosphole 2-oxide (95a) in the lowest yield. The (E)-prop-1-enylphosphonodiamide 96 also underwent the RCM well. However, N,N’-dicinnamyl-vinylphosphonodiamides 94b,c (R’ = H, Me, R = Ph) always generated the corresponding N,N’-dicinnamyl-styrylphosphonodiamides 98 in 12–17% yields as byproducts via the RCM

Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• was stirred at room temperature for 12 h, then water (15 mL) was added to the mixture, and stirring was continued for 5 min. The reaction mixture was acidified with conc. HCl to pH 2 and extracted with DCM. The extract was washed with brine, dried over Na2SO4, and evaporated under reduced pressure

• ) at 0–5 °C a solution of KOH (0.392 g, 7 mmol) in H2O (1 mL) was added dropwise under stirring. The reaction mixture was stirred at this temperature for 1–4 h (in the case of ester 7 it was stirred at room temperature for 96 h), then acidified with conc. HCl to pH 5–6. The resultant precipitate was

• filtered. To the filtrate the corresponding ester 20–24 (1 mmol) was added. The reaction mixture was stirred at 0–5 °C for 1 h, then the solvent was removed under reduced pressure, the residue was dissolved in water, cooled to 0–5 °C and acidified with conc. HCl to pH 5–6. The resultant precipitate was

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• ), DPPPy-Ph-3F (17), and DPPPy-Ph-F (18, Figure 8), and determined the 11B NMR spectra (Figure 9c) [44]. When coordinated with nitrogen atoms, the resonance peak shifted slightly from ca. −10 to 0 ppm, which suggested the interaction between boron and nitrogen atoms. Wang’s group studied the interaction of

• )3 at different temperatures from 300 to 230 K. (c) 11B NMR spectra of B(C6F5)3, DPPPy-Py-F (compound 16)/B(C6F5)3, DPPPy-Ph-3F (compound 17)/B(C6F5)3, and DPPPy-Ph-F (compound 18)/B(C6F5)3 in CD2Cl2, respectively. Figure 9a and 9b were reprinted with permission from [43], Copyright 2011 American

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• synthetic chemistry, we report the synthesis of a series of bench-stable α-(perfluoroalkylsulfonyl)propiophenones. Their application as photocleavable reagents was tested with electron-rich aromatics under metal-free, redox- and pH-neutral conditions to enable late-stage perfluorooctylation

• halogenation reactions or oxidation. For these reasons, it would be ideal to develop an efficient methodology that allows for the generation of perfluoroalkyl radicals in a mild, redox- and pH-neutral manner, without the assistance of external photocatalysts, heavy metal catalysts, or further additives. Thus

• reactivity of these molecules allows this set of reagents to be both redox- and pH-neutral, while also being highly diversifiable. Additionally, all byproducts generated either during its synthesis or use in following reactions have the potential to be recycled, if so desired. Based on the fact that both

Synthesis of bis-spirocyclic derivatives of 3-azabicyclo[3.1.0]hexane via cyclopropene cycloadditions to the stable azomethine ylide derived from Ruhemann's purple

• Alexander S. Filatov,
• Olesya V. Khoroshilova,
• Anna G. Larina,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2022, 18, 769–780, doi:10.3762/bjoc.18.77

• asymmetric 1,3-dipolar cycloaddition of azomethine ylides and cyclopropenes catalyzed by a chiral Cu-(CH3CN)4BF4/Ph-Phosferrox complex for the construction of 3-azabicyclo[3.1.0]hexane derivatives [25]. Another concise enantioselective approach towards 3-azabicyclo[3.1.0]hexanes is based on a Cp*Ir-catalyzed