Germacrene B – a central intermediate in sesquiterpene biosynthesis

• Houchao Xu and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18

• synthesis from β-eudesmol (30) through epoxidation to 31, dehydration to 32 and epoxide opening with LiAlH4 yielded (−)-11 (Scheme 9C) [77], contradicting this assignment. Notably, Šorm and co-workers noticed that 11 was racemic, because neither 11 nor any of its degradation products showed optical activity

The stereochemical course of 2-methylisoborneol biosynthesis

• Binbin Gu,
• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 818–824, doi:10.3762/bjoc.18.82

• bound substrate surrogate 2FGPP (generated with Pymol from the crystal structure, PDB code: 3V1X). B) Isomerization of 2-Me-GPP to (S)-2-Me-LPP, the hypothetical enantiomer expected for 2-Me-GPP in the same conformation as observed for 2FGPP. Structures of 2MIBS side products and spontaneous degradation

• products of 2-Me-LPP. The enantiomers shown are the expected on-pathway intermediates towards 1. Total ion chromatograms of extracts from an incubation of A) enantiomerically pure (R)-2-Me-LPP with 2-MIBS, B) enantiomerically pure (S)-2-Me-LPP with 2-MIBS, and C) enantiomerically pure (R)-2-Me-LPP without

Targeting active site residues and structural anchoring positions in terpene synthases

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 2441–2449, doi:10.3762/bjoc.17.161

• activation. DHFPP = 2,3-dihydro-FPP. The products of SmTS1. A) Structures of sestermobaraenes A–F (1–6) and sestermobaraol (7). B) The total ion chromatogram of the products obtained with SmTS1 from GFPP. Peak labels a, b and c indicate unknown products, asterisks indicate degradation products from GFPP that

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• work is testified by Willstätter, who in his memoirs refers to Guareschi as “alkaloid chemist” [28]. Ptomaines (from the Greek πτωμα, cadaver) are anaerobic bacterial degradation products of proteins and choline-containing phospholipids. The formation of these is associated with putrefaction of animal

Synthetic accesses to biguanide compounds

• Oleksandr Grytsai,
• Cyril Ronco and
• Rachid Benhida

Beilstein J. Org. Chem. 2021, 17, 1001–1040, doi:10.3762/bjoc.17.82

• such as lead tetraacetate, potassium permanganate, or refluxing hydrogen peroxide were shown to produce urea-derived degradation products [3]. Biguanides also possess a remarkable capability to form stable metal complexes, a property that was already noticed by B. Rathke in 1879 [4]. Indeed, he relied

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• relationship during which the antibiotic TDA and growth stimulants are produced to a pathogenic interaction promoted by lignin degradation products in fading algal blooms that induce roseobacticide biosynthesis [36]. All these examples demonstrate the importance of sulfur metabolism for marine bacteria from

• its saturated analog 6-methylheptan-2-one (35) was only emitted by C. baekdonensis and geranylacetone (36) only by the three productive species C. marinus, C. neptunius, and C. manganoxidans. Compounds 34 and 36 have been described as non-enzymatic degradation products arising from the side chain in

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• accessible; however, it is possible that important biotransformation products may not to be detected using these techniques. For example, the fluorometabolites detected upon fungal degradation of cyhalothrin were not observed by GC–MS of culture supernatants. When the nature of the degradation products is

Ring-closing metathesis of prochiral oxaenediynes to racemic 4-alkenyl-2-alkynyl-3,6-dihydro-2H-pyrans

• Viola Kolaříková,
• Markéta Rybáčková,
• Martin Svoboda and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2020, 16, 2757–2768, doi:10.3762/bjoc.16.226

• tert-butyldiphenylsilyl ether according to reference [32] or with a tetrahydropyranyl group. In both cases, we obtained the target products 7a and 8a in nearly quantitative yields. Interestingly, a reaction time over 1 h in the THP protection led to the formation of degradation products and a

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• those of synthetically prepared model imidazoles. The absolute configurations of the anteisoalkanoyl group present in 1, 4, and 5 were determined by low-temperature HPLC analysis of the degradation products labeled with a chiral anthracene reagent, which revealed that 1 is a mixture of the R- and S

Tuneable access to indole, indolone, and cinnoline derivatives from a common 1,4-diketone Michael acceptor

• Dalel El-Marrouki,
• Sabrina Touchet,
• Abderrahmen Abdelli,
• Hédi M’Rabet,
• Mohamed Lotfi Efrit and
• Philippe C. Gros

Beilstein J. Org. Chem. 2020, 16, 1722–1731, doi:10.3762/bjoc.16.144

• catalysts with different acidities (Table 1, entries 1–5). Among them, only acetic acid afforded reaction products, while the others only produced complex mixtures of degradation products. Under the conditions of entry 5, the indole 6b was isolated in 47%, and the indolone 7b was also formed concomitantly

• aprotic solvents, other than toluene (Table 1, entries 7 and 8), the reaction produced complex mixtures of degradation products, and using alcohols had a notable impact on the reaction contents. Indeed, going from ethanol to propanol, and thus increasing the refluxing temperature, led to the indolone 7b

Antibacterial scalarane from Doriprismatica stellata nudibranchs (Gastropoda, Nudibranchia), egg ribbons, and their dietary sponge Spongia cf. agaricina (Demospongiae, Dictyoceratida)

• Cora Hertzer,
• Stefan Kehraus,
• Nils Böhringer,
• Fontje Kaligis,
• Robert Bara,
• Dirk Erpenbeck,
• Gert Wörheide,
• Till F. Schäberle,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2020, 16, 1596–1605, doi:10.3762/bjoc.16.132

• -methylenedeoxoscalarin was determined. It needs to be noted that the molecule was unstable over time, especially in ring E, and a variety of degradation products formed by, inter alia, hydrolysis of the hemiacetal and loss of the acetoxy groups. The new scalarane was also detected in Doriprismatica stellata egg ribbons

Characterization of two new degradation products of atorvastatin calcium formed upon treatment with strong acids

• Jürgen Krauß,
• Monika Klimt,
• Markus Luber,
• Peter Mayer and
• Franz Bracher

Beilstein J. Org. Chem. 2019, 15, 2085–2091, doi:10.3762/bjoc.15.206

• structures of the degradation products. Here we report the identification of two novel degradation products of atorvastatin, which are formed only under drastic acidic conditions. While treatment with conc. sulfuric acid led to a loss of the carboxanilide residue (accompanied by an expectable lactonization

• /dehydration process in the side chain), treatment with conc. aqueous hydrochloric acid gave a complex, bridged molecule under C–C-bond formation of the lactone moiety with the pyrrole, migration of the isopropyl group and loss of the carboxanilide residue. The novel degradation products were characterized by

• NMR spectroscopy, HRMS data and X-ray crystal structure analysis. Keywords: atorvastatin; crystal structure; cyclization; degradation products; fragmentation; stress test; Introduction Over the past decades, the general trend toward globalization of the supply chains for active pharmaceutical

Regioselective Pd-catalyzed direct C1- and C2-arylations of lilolidine for the access to 5,6-dihydropyrrolo[3,2,1-ij]quinoline derivatives

• Hai-Yun Huang,
• Haoran Li,
• Thierry Roisnel,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2019, 15, 2069–2075, doi:10.3762/bjoc.15.204

• structure of 2 was confirmed by X-ray analysis. A lower yield of 7 was obtained for the reaction of 4-bromobenzaldehyde with lilolidine due to the formation of degradation products. Good yields in 8 and 9 were obtained from 4-chloro- and 4-carbonitrile-substituted aryl bromides. In all cases, with these

Norbornadiene-functionalized triazatriangulenium and trioxatriangulenium platforms

• Roland Löw,
• Talina Rusch,
• Tobias Moje,
• Fynn Röhricht,
• Olaf M. Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1815–1821, doi:10.3762/bjoc.15.175

• s−1 under air and 0.95·10−3 s−1 under nitrogen. Hence, the thermal reaction (in contrast to the photochemical reaction) is not largely affected by oxygen. The half-life of the metastable quadricyclane is t1/2 = 655 h in benzene under air at 293 K (Table 1). Minor amounts of degradation products (<1

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• above, we have never observed the formation of degradation products. (ii) The reaction was performed in water, in the presence of SDS (sodium dodecyl sulfate) as the surfactant. Based on previous studies [35], the most effective method for ensuring the solubility of reactants in water is the use of

Phosphoramidite building blocks with protected nitroxides for the synthesis of spin-labeled DNA and RNA

• Timo Weinrich,
• Eva A. Jaumann,
• Ute M. Scheffer,
• Thomas F. Prisner and
• Michael W. Göbel

Beilstein J. Org. Chem. 2018, 14, 1563–1569, doi:10.3762/bjoc.14.133

• , each with 100 mW optical output power [41]. 20 min irradiation in 10 mM phosphate buffer, pH 7.4). Subsequent elimination of formic aldehyde and air oxidation transformed these intermediates into nitroxides 22c–27c. Amines 22d–27d, typical degradation products of nitroxides, could not be detected

Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)

• Alexander Bogdanov,
• Cora Hertzer,
• Stefan Kehraus,
• Samuel Nietzer,
• Sven Rohde,
• Peter J. Schupp,
• Heike Wägele and
• Gabriele M. König

Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50

• data with the literature reports [31][32][33][34][35][36]. Repeated HPLC separation of VLC fraction 7 firstly led to two metabolites, which could not be structurally analyzed due to their instability. It was noted however, that two stable degradation products resulted and could be isolated, i.e

Regiocontroled Pd-catalysed C5-arylation of 3-substituted thiophene derivatives using a bromo-substituent as blocking group

• Mariem Brahim,
• Hamed Ben Ammar,
• Jean-François Soulé and
• Henri Doucet

Beilstein J. Org. Chem. 2016, 12, 2197–2203, doi:10.3762/bjoc.12.210

• °C, and a reaction time of 15 h, the desired C5-arylated product 1 was formed in only 8% yield due again to the formation of several degradation products (Table 1, entry 2). Then, we examined the influence of the reaction time. After 2 or 4 h, higher yields of 1 (55% and 48%) were obtained

Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4

• Elena N. Sigida,
• Yuliya P. Fedonenko,
• Alexander S. Shashkov,
• Nikolay P. Arbatsky,
• Evelina L. Zdorovenko,
• Svetlana A. Konnova,
• Vladimir V. Ignatov and
• Yuriy A. Knirel

Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62

• above), elimination of the side-chain Glc and cleavage of the linkage of the destroyed 2-substituted Xyl were expected. Fractionation of the Smith degradation products by TSK HW-40 (S) gel-permeation chromatography resulted in a mixture of the expected oligosaccharides 1 and 2 and higher molecular mass

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• degradation temperatures were chosen: a low temperature of 50 °C and a high temperature of 150 °C. The degradation time was 2 h. After the degradation reaction and cooling of the samples, the degradation products were extracted with 4 mL of hexane. The solution was dried over anhydrous sodium sulfate and

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• formation. Its potential use in pharmaceutical applications and food industry is closely related to the stability of the compound. Curcumin is not stable under physiological conditions and its degradation products are depicted in Figure 1a [10]. With the aim of improving the chemical stability and

• dehydrozingerone (2). In conclusion, from the results obtained we can conclude that the type of linkage between the two “halves” by which the molecule is made up does not exert influence on the antioxidant efficiency and reactivity of the two dimers. a) Degradation products of curcumin according to Wang et al. [10

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

• Marcelo Isidoro P. Reis,
• Vinícius R. Campos,
• Jackson A. L. C. Resende,
• Fernando C. Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137

• between 1,3,5-triazinanes 14–19 and 2-hydroxy-1,4-naphthoquinone (20) was developed to prepare fused hexahydropyrimidine-1,4-naphthoquinones 13 and 21–25 using in situ generated alkyl formimines. Performing the reaction without heating proceeds very slow and after 24 hours extensive degradation products

Properties of cationic monosubstituted tetraalkylammonium cyclodextrin derivatives – their stability, complexation ability in solution or when deposited on solid anionic surface

• Martin Popr,
• Sergey K. Filippov,
• Nikolai Matushkin,
• Juraj Dian and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2015, 11, 192–199, doi:10.3762/bjoc.11.20

• stability of the PEMPDA-β-CD derivative. The TLC after 20 h showed a spot of the starting compound, while the degradation of PEMEDA-β-CD was already complete. We managed to separate the degradation products on a column of silica gel and identified them by ESIMS (Scheme 1). To determine the decomposition

Release of β-galactosidase from poloxamine/α-cyclodextrin hydrogels

• César A. Estévez,
• José Ramón Isasi,
• Eneko Larrañeta and
• Itziar Vélaz

Beilstein J. Org. Chem. 2014, 10, 3127–3135, doi:10.3762/bjoc.10.330

• systems because biocompatible polymers are gradually absorbed by the body with no need for a subsequent surgical removal. However, these systems can also present some disadvantages depending on the nature of the degradation products, which can be toxic, immunogenic or carcinogenic [15]. In this work, our

Palladium-catalyzed 2,5-diheteroarylation of 2,5-dibromothiophene derivatives

• Fatma Belkessam,
• Aidene Mohand,
• Jean-François Soulé,
• Abdelhamid Elias and
• Henri Doucet

Beilstein J. Org. Chem. 2014, 10, 2912–2919, doi:10.3762/bjoc.10.309

• degradation products. The use of 6 equiv of thiophene allowed the formation of 2,2':5',2"-terthiophene (7) in 85% yield. The reactivity of three furan derivatives was also studied using PdCl(C3H5)(dppb) as the catalyst. From 2-n-butylfuran, 8 was obtained in 79% yield, whereas 2-acetylfuran and methyl 2

• and 15 in 83% and 80% yields, respectively. The four terthiophenes 16–19 were also obtained in satisfactory yields. Again a moderate yield in 20 was obtained in the presence of methyl 2-methylfuran-3-carboxylate due to the formation of degradation products, whereas the reaction with 1-methylpyrrole