Efficient synthesis of dipeptide analogues of α-fluorinated β-aminophosphonates

• Marcin Kaźmierczak and
• Henryk Koroniak

Beilstein J. Org. Chem. 2020, 16, 756–762, doi:10.3762/bjoc.16.69

• at room temperature. What is more, we attempted to crystallize at least one derivative to confirm the absolute stereochemistry of the obtained compounds. In order to obtain a single crystal suitable for X-ray diffraction studies, various crystallization techniques were tested [37][38

• ]. Crystallization of derivative 14c from D2O brought the expected results. The analysis confirmed the structure of the resulting compound 14c. The absolute configuration of 14c is consistent with the stereochemistry we proposed based on NMR studies. The crystals of 14c contained the (1R,2S)-diastereoisomer (Figure

Synthesis of C₇₀-fragment buckybowls bearing alkoxy substituents

• Yumi Yakiyama,
• Shota Hishikawa and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

• vapour diffusion method using CHCl3/hexane conditions. Figure 2 shows the crystal structure of 5a. The crystal was obtained as a racemic compound containing a pair of two enantiomers defined by bowl chirality [26], as a result of the rapid bowl inversion under the crystallization conditions. 5a formed a

Direct borylation of terrylene and quaterrylene

• Haruka Kano,
• Keiji Uehara,
• Kyohei Matsuo,
• Hironobu Hayashi,
• Hiroko Yamada and
• Naoki Aratani

Beilstein J. Org. Chem. 2020, 16, 621–627, doi:10.3762/bjoc.16.58

• ]. However, the crude product was not completely purified by Soxhlet extraction and by crystallization in our hands. The borylation reaction of hardly soluble crude quaterrylene gave a deep green suspension. MALDI mass spectrometry of the reaction mixture detected an ion peak at m/z = 1004.5018 (calcd for

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• preferably refers to the solubility in the surrounding matrix, while undesirable events such as aggregation are of minor importance. In the worst case, it can also result in crystallization of the cyanine in the matrix under certain storage conditions such as high humidity and/or elevated temperatures

Architecture and synthesis of P,N-heterocyclic phosphine ligands

• Wisdom A. Munzeiwa,
• Bernard Omondi and
• Vincent O. Nyamori

Beilstein J. Org. Chem. 2020, 16, 362–383, doi:10.3762/bjoc.16.35

• . Finally, the desired ligands were obtained by palladium-catalyzed phosphorylation with triphenylphosphine in DMF [92]. Resolution with palladium amine complexes and subsequent crystallization resulted in the enantiomerically pure ligands 95. C2-Symmetric atropisomeric diphosphines are among a diverse

Absolute configurations of talaromycones A and B, α-diversonolic ester, and aspergillusone B from endophytic Talaromyces sp. ECN211

• Ken-ichi Nakashima,
• Junko Tomida,
• Takao Hirai,
• Yoshiaki Kawamura and
• Makoto Inoue

Beilstein J. Org. Chem. 2020, 16, 290–296, doi:10.3762/bjoc.16.28

• absolute configurations of the new derivatives 1 and 2 using extensive spectroscopic analyses as well as single-crystal X-ray diffractometry. Our crystallization efforts resolved the absolute configuration of α-diversonolic ester (3) and its derivatives, which had not been clarified previously

Halogen-bonding-induced diverse aggregation of 4,5-diiodo-1,2,3-triazolium salts with different anions

• Xingyu Xu,
• Shiqing Huang,
• Zengyu Zhang,
• Lei Cao and
• Xiaoyu Yan

Beilstein J. Org. Chem. 2020, 16, 78–87, doi:10.3762/bjoc.16.10

• halogen acceptors was also investigated. Diffusion of ether into the mixture of 4,4'-bipyridine (bpy) and 2-BF4 in dichloromethane leads to the crystallization of 2-BF4·0.5bpy (Figure 8). It crystallizes in the monoclinic space group P21/c. The acceptor 4,4'-bipyridine provides a complementary link for 1D

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• with toluene (3 × 100 mL). A final crystallization from EtOH yielded the title compound (4.69 g, 89%). 1H NMR (CDCl3, 200 MHz) δ 7.30–7.42 (m, 10H, CHAr), 6.75 (d, J = 9.2 Hz, 2H, CHAr), 6.43–6.48 (m, 4H, CHAr), 4.97 (s, 4H, CH2), 4.18 (s, 4H, CH2), 4.14 (s, 8H, CH2), 4.06 (q, J = 7.2 Hz, 8H, CH2

A chiral self-sorting photoresponsive coordination cage based on overcrowded alkenes

• Constantin Stuckhardt,
• Diederik Roke,
• Wojciech Danowski,
• Edwin Otten,
• Sander J. Wezenberg and
• Ben L. Feringa

Beilstein J. Org. Chem. 2019, 15, 2767–2773, doi:10.3762/bjoc.15.268

• supramolecular palladium complexes caused immediate crystallization [22]. Moreover, azobenzenes have been used to functionalize both the interior [23] and exterior [24] of SCCs to photochemically control guest binding and release. Furthermore, incorporation of dithienylethene into the ligands connecting the

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• volatile solvents removal, (iii) the high temperature crystallization step for 90 minutes. Spherical nanoparticles of 21.8 ± 1.3 nm were collected. Crystal quality was assayed by XRD and only the hexagonal β-phase could be detected (Supporting Information File 1). These particles are kept well dispersed in

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• fractionating crystallization. Structure determination by X-ray diffraction analysis revealed marked conformational differences around the CH–C(O–) single bond of E and Z-isomers and extended charge delocalization in the anionic part. Keywords: betaines; multi-component reactions; N-triflylamides; phospha

• E-diastereoisomers, others as E/Z mixtures. In some cases, the two diastereoisomers were separated by fractionating crystallization from a mixed-solvent solution. In the case of 3a, a trace amount (≈2%) of the Z-isomer was detected in the reaction mixture by 1H NMR (the chemical shift of the

Chiral terpene auxiliaries V: Synthesis of new chiral γ-hydroxyphosphine oxides derived from α-pinene

• Anna Kmieciak and
• Marek P. Krzemiński

Beilstein J. Org. Chem. 2019, 15, 2493–2499, doi:10.3762/bjoc.15.242

• (III) chloride in methanol in 88% yield (Scheme 1). The synthesis of allylic alcohol 11, a regioisomer of 6, started again from (1R)-α-pinene (1, Scheme 2). Hydroboration of (1R)-α-pinene with borane–dimethyl sulfide adduct (BMS) and crystallization of the product diisopinocampheylborane (dIpc2BH, 84

• added to the reaction mixture and the solution was filtered through a pad of celite. The precipitate was washed with another portion of warm toluene (10 mL). The solvent was removed using a rotary evaporator to give the phosphine oxide. After crystallization from heptane, phosphine oxide 21 (1.612 g, 92

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• –124 °C (methanol used for crystallization); 1H NMR (600.25 MHz, CDCl3, 25 °C) δ 5.653 (dddd, 3J8,9a = 17.0 Hz, 3J8,9b = 10.2 Hz, 3J8,7b = 7.3 Hz, 3J8,7a = 6.9 Hz, 1H, H-8), 5.449 (dd, 3J4’,3’ = 3.4 Hz, 3J4’,5’ = 1.2 Hz, 1H, H-4’), 5.416 (dd, 3J3,2 = 7.5 Hz, 3J3,4 = 3.3 Hz, 1H, H-3), 5.308 (dd, 3J4,5

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• (H2B(pz)2)2”, with its β-keto ester moiety acting as a second coordination site. Slow crystallization yielded a tetranuclear Fe(II) complex 9, where the base dimeric unit is expanded by an unprecedented trimethoxypyrazolylborate bridging group. The photocyclization of iron complexes is inhibited due to

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

• Irina G. Tkachenko,
• Sergey A. Komykhov,
• Vladimir I. Musatov,
• Svitlana V. Shishkina,
• Viktoriya V. Dyakonenko,
• Vladimir N. Shvets,
• Mikhail V. Diachkov,
• Valentyn A. Chebanov and
• Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

• spectra were measured on a GC–MS Varian 1200L (ionizing voltage 70 eV, direct input of the sample) instrument. Elemental analysis was realized on a EuroVector EA-3000. Analytical samples of the compounds were obtained by crystallization from water and further drying at room temperature in air. Microwave

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• subsequent cyclization unlikely. Crystal structure of CotB2wt·Mg2+3·F-Dola resembles the closed, active conformation The structure of CotB2wt·Mg2+3·F-Dola has been obtained by co-crystallization of CotB2wt and FGGDP (PDB-ID 6GGI; [37]), representing the closed, active conformation. Fluorinated substrates

• , such as FGGDP, have been used for the crystallization of other TPSs and have been shown to stick to the active site without undergoing cyclization, trapping the enzyme in a closed state [52][53]. Comparing the overall structure of CotB2wt·Mg2+3·F-Dola to the open conformation of CotB2 reveals major

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• state, as envisioned. Possible reasons could be assigned to substituent effects as demonstrated by Simeth et al. [62]. As recently reported by Schehr et al., reducing agents like DTT, used to prevent enzyme oxidation in crystallization mixtures or in vitro assays, can reduce azo dyes to hydrazine

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• THTAA Derivative 3 was prepared from 2,5-dihydroxy-p-benzoquinone and ethylenediamine as brownish-yellow solid according to the recommended procedure (Scheme 1) [8]. Crystallization from butyl acetate produced yellow crystals of THTAA (3) in about 50% yield, still slightly brownish, along with the

Attempted synthesis of a meta-metalated calix[4]arene

• Christopher D. Jurisch and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2019, 15, 1996–2002, doi:10.3762/bjoc.15.195

• literature report [32]). This was presumably due to ruthenium undergoing a reductive elimination and the chloride remaining on the triazolium moiety. Crystallization also proved to be futile after many attempts under many different conditions. The only crystals that formed were either found to be the

Halide metathesis in overdrive: mechanochemical synthesis of a heterometallic group 1 allyl complex

• Ross F. Koby,
• Nicholas R. Rightmire,
• Nathan D. Schley,
• Timothy P. Hanusa and
• William W. Brennessel

Beilstein J. Org. Chem. 2019, 15, 1856–1863, doi:10.3762/bjoc.15.181

• of [KA'] and alkali metal iodides, extracting the ground mixtures with hydrocarbon solvents, and then attempting crystallization of the extracts. This is necessarily an imperfect route to sampling the product space, as definitive characterization of any product(s) depended critically on the

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• [16][18][19], isopropyl 5c [16] and tert-butyl 5d [16][20] as well as for 4-methoxyphenyl ester 5e [21]. However, the corresponding (−)-menthyl esters (2R,1'R)-5f and (2S,1'R)-5f were separated by solvent-driven selective crystallization at low-temperature from ethanol and hexane, respectively. The

• presence of acetic anhydride produced a crude acetamido ester (R)-132 which was transformed into the final N-benzyl amide (R)-130 with of 99.9% ee after crystallization. ʟ-(+)-Furanomycin (Scheme 35) is a natural nonproteinogenic amino acid which showed pronounced antibacterial activity. From several

• pyrrolidin-2-ones (3S,4R,5R,1'R)-183b (by crystallization from cold ethanol) and (3R,4S,5R,1'R)-183b (by flash chromatography). After reduction and hydrogenolysis they were converted into 1,4-dideoxy-1,4-imino-ᴅ-arabinitol and ((2R,3R,4R)-182) and 1,4-dideoxy-1,4-imino-ᴅ-xylitol ((2R,3S,4S)-182

Molecular basis for the plasticity of aromatic prenyltransferases in hapalindole biosynthesis

• Takayoshi Awakawa and
• Ikuro Abe

Beilstein J. Org. Chem. 2019, 15, 1545–1551, doi:10.3762/bjoc.15.157

• , an X-ray crystallization analysis was conducted. The apo structure of AmbP1 was solved at 2.35 Å, and it adopted an ABBA fold [4][5][13]. Interestingly, the apo structure unusually includes the Mg2+ ion in a position nearby the β-barrel, stabilized by hydrogen bonding with N41, E63, and D65 (Figure

• same pH as in the reservoir for crystallization. In this structure (Mg2+-free structure), the distance from C-1 of GSPP to C-2 of 1 (Figure 4A, a: 3.3 Å) is closer than that to C-3 of 1 (Figure 4A, b: 4.6 Å), unexpectedly indicating that this is a model for the C-2 prenylation. Next, the soaking

Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• the inclusion of the base led to crystallization of the corresponding products 3a–c during the milling process. In contrast, crystallization during the base-free reaction required an ex situ aging step. Figure 1 shows the XRPD pattern of the substrate 2 and the product 3a. Due to the liquid state of

• inclusion of base catalyst in the final product, we suggest this difference to be the result of a templating effect, which dominates at higher concentrations. For the reaction of meta- and ortho-substituted substrates, crystallization occurs directly into the monoclinic phase, regardless of milling

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• dispersion and crystallization of CB[7] and PCL in the composite nanofibers, XRD patterns of neat PCL nanofibers and all PCL/CB[7] nanofibers were recorded (Figure 2). PCL is a semi-crystalline polymer, and neat PCL nanofibers elicit two strong and sharp characteristic diffraction peaks at 2θ = 22° and 2θ

• continuous phase and crystal aggregates of PCL and CB[7]. At low CB[7] contents, the majority of the CB[7] molecules could disperse homogeneously in the PCL matrix, partly causing the disruption of continuous phase and crystallization of PCL and CB[7]. With the increase of CB[7] content, there are more

• that temperature. There is only a very wide and weak peak in the heating cycle, which was caused by evaporating of water from the cavity of CB[7] (Figure S7 in Supporting Information File 1). As can be deduced from Figure 3, all electrospun webs exhibit obvious melting and crystallization peaks below

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• . employing substitutional disorder, achieved the co-crystallization of six components [28]. As for positional disorder, it generally indicates the same molecule or assembly can adopt more than one favourable conformation. From this perspective, disorder can be considered as a special case of a co-crystal or