The scent gland composition of the Mangshan pit viper, Protobothrops mangshanensis

• Jonas Holste,
• Paul Weldon,
• Donald Boyer and
• Stefan Schulz

Beilstein J. Org. Chem. 2024, 20, 2644–2654, doi:10.3762/bjoc.20.222

• . The synthesis of methyl 4,6-dimethyldodec-5-enoate allowed the correct assignment of structures and showed the (E)-configuration of the double bond for the major naturally occurring diastereomers. These acids occur in small amounts compared to the major glandular components, cholesterol, and 1-O

• between H-5 (4.82 ppm) and C-6-methyl (1.66 ppm) (Supporting Information File 1, Figure S11) for the minor compound eluting earlier in GC, indicating that both hydrogen atoms are close together and that the double bond has a Z-configuration. The other diastereomer showed no coupling between H-5 (4.84 ppm

• . The major component Dm of the methylated secretion with I 1595 was therefore assigned to have the E configuration. The E/Z ratio Dm/Dm’ in all samples was about 20:1. In all cases the second eluting diastereomer of compounds Am–Fm was present in higher proportions, indicating a preferred E

Deciphering the mechanism of γ-cyclodextrin’s hydrophobic cavity hydration: an integrated experimental and theoretical study

• Stiliyana Pereva,
• Stefan Dobrev,
• Tsveta Sarafska,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2024, 20, 2635–2643, doi:10.3762/bjoc.20.221

• enlarging the aperture (“open” configuration). In the “open” configuration, the primary hydroxy groups are not involved in the intramolecular hydrogen-bonding interactions with neighboring OH groups. Relatively weak hydrogen bonds are formed between the secondary hydroxy groups at the wider/lower rim of the

• energetically more favorable than the “open” configuration (by 22.3 kcal mol−1), which is why the “head–tail” structure was used in subsequent evaluations. It should be noted that for the two conformers modelled, the “closed” one has the typical truncated cone shape whereas the open one is more like a cylinder

Base-promoted cascade recyclization of allomaltol derivatives containing an amide fragment into substituted 3-(1-hydroxyethylidene)tetronic acids

• Andrey N. Komogortsev,
• Constantine V. Milyutin and
• Boris V. Lichitsky

Beilstein J. Org. Chem. 2024, 20, 2585–2591, doi:10.3762/bjoc.20.217

• synthesized products is different from previously described 3-acetyltetronic acids 2 obtained from the corresponding hydrazides 1. As well as in the case of compounds 2 for the amide derivatives 4 the double bond between pyrrolidinone and furanone parts has E-configuration. Only for sterically hindered

• 2 are easily deacetylated under reflux in MeOH for 8 h. At the same time the compounds 4 described in the present communication are more stable and under these conditions the loss of the acetyl group was not observed. It can be supposed that described above difference in configuration of the enol

• refluxing EtOH allowed us to obtain substituted enehydrazine 7 (Scheme 5a). The similar condensation with amine 8 led to enamine derivative 9 (Scheme 5b). Based on the data of X-ray analysis compound 7 has the same configuration of double and hydrogen bonds as in the case of starting tetronic acids 4

Photoredox-catalyzed intramolecular nucleophilic amidation of alkenes with β-lactams

• Valentina Giraldi,
• Giandomenico Magagnano,
• Daria Giacomini,
• Pier Giorgio Cozzi and
• Andrea Gualandi

Beilstein J. Org. Chem. 2024, 20, 2461–2468, doi:10.3762/bjoc.20.210

• ][41][42][43]. The inhibitory activity of β-lactamases is exhibited by those congeners with a (3R,5R)-configuration, such as clavulanic acid (1), whereas clavams with other configurations are not lactamase inhibitors, although some of these have antifungal or antibacterial properties [35]. In the

• chemical shifts of these protons in the two isomers could be attributed to the influence of the anisotropy of the neighboring carboxy group of the β-lactam and could be correlated with the configuration at the bridgehead stereocenter [46]. This analysis revealed the preferred formation of the trans- over

• -diastereoisomer was favored. In this study, enantiopure 3-(1’-(tert-butyldimethylsilyl)ethyl)-β-lactams 10c–f were also tested. Products 12c–f were obtained with moderate to good yield, underscoring the feasibility of the methodology for the C3-substituted β-lactam moiety. The configuration at the newly formed

Synthesis and conformational analysis of pyran inter-halide analogues of ᴅ-talose

• Olivier Lessard,
• Mathilde Grosset-Magagne,
• Paul A. Johnson and
• Denis Giguère

Beilstein J. Org. Chem. 2024, 20, 2442–2454, doi:10.3762/bjoc.20.208

• , therefore we were compelled to proceed directly to the next step. Cleavage of the 1,6-anhydro bridges was achieved under acetolysis conditions providing halogenated talopyranoses 12–15 in good yield over 3 steps as α anomers. Luckily, inter-halides 13–15 were crystalline, allowing the absolute configuration

Asymmetric organocatalytic synthesis of chiral homoallylic amines

• Nikolay S. Kondratyev and
• Andrei V. Malkov

Beilstein J. Org. Chem. 2024, 20, 2349–2377, doi:10.3762/bjoc.20.201

• securing the enantioselectivity of the reaction by locking the catalyst in the more active and enantioselective Z-configuration (Figure 2). Further, the authors found that H-bond donors featuring urea, thiourea, and guanidine motifs were either inactive or provided racemic mixtures. Among 3,5-dichloro

• absolute configurations of homoallylamines 66 were assigned by analogy to 67, the configuration of which was determined after removal of the N-aryl group and comparing the optical rotation with the literature values for the known enantiomer (S)-69 (Scheme 14). The proposed stereochemical model suggests

• ’-dibromo-BINOL [25]. aAbsolute configuration was confirmed by a single crystal XRD of the corresponding hydrochloride salt. (R)-3,3’-Di(3,5-di(trifluoromethyl)phenyl-BINOL-catalysed asymmetric geranylation and prenylation of dihydroisoquinolines [25]. aAbsolute configuration was established by single

Stereoselective mechanochemical synthesis of thiomalonate Michael adducts via iminium catalysis by chiral primary amines

• Michał Błauciak,
• Dominika Andrzejczyk,
• Błażej Dziuk and
• Rafał Kowalczyk

Beilstein J. Org. Chem. 2024, 20, 2313–2322, doi:10.3762/bjoc.20.198

• proved by X-ray studies. Assuming the mechanism of addition is similar in the case of other nucleophiles, the configuration of others was assigned by analogy. More sterically demanding di-tert-butyl thiomalonate (2) reacted in a similar fashion as the dibenzyl thiomalonate (1), leading also to desired

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

• only due to its structural analogy to the other lysilactones; it is not a resorcylic lactone and has not been mentioned after the initial report [139]. The structures of these compounds were determined by NMR-spectroscopic methods and constitution and configuration of lysilactone A was further

• block (Figure 12). The verrulactones were isolated from Penicillium verruculosum [187][193][221] and verrulactone A and B were further isolated from Alternaria alternata [159][160]. Constitution and relative configuration of these compounds was determined by NMR-spectroscopic methods, where the

• as in isoaltenuene [251] had to be corrected after total synthesis [249] and comparison of measured and calculated ECD spectra [162]. The revised absolute configuration of (−)-altenuene is given in Figure 14. Altenuene was isolated in various Alternaria spp., i.e., not only in A. alternata, but

Computational toolbox for the analysis of protein–glycan interactions

• Ferran Nieto-Fabregat,
• Maria Pia Lenza,
• Angela Marseglia,
• Cristina Di Carluccio,
• Antonio Molinaro,
• Alba Silipo and
• Roberta Marchetti

Beilstein J. Org. Chem. 2024, 20, 2084–2107, doi:10.3762/bjoc.20.180

• , depending on the values adopted by the torsional angles around the glycosidic linkages [10]. The high variability of linkages type, branching, stoichiometry, anomeric configuration (alpha and beta), and conformation contributes to the intricate nature of glycans. The complexity of the glycome is even higher

• able to add branching points and some sugar derivatisation, including methylation and acetylation. The user has also the possibility to choose the ring type and the anomeric configuration of each monosaccharide. Once the structure is complete, it is possible to download not only the generated .pdb

1,2-Difluoroethylene (HFO-1132): synthesis and chemistry

• Liubov V. Sokolenko,
• Taras M. Sokolenko and
• Yurii L. Yagupolskii

Beilstein J. Org. Chem. 2024, 20, 1955–1966, doi:10.3762/bjoc.20.171

• Haszeldine et al. [49][100]. The reaction of individual E- or Z-isomer of 1,2-difluoroethylene and fluorinated ketones (Scheme 21) led to a mixture of stereoisomers in both cases, although for the E-isomer, about 70% of the product retained the starting configuration. Overall, (E)-1,2-difluoroethylene had

• hexafluorodiacetyl under UV irradiation, yielding a mixture of five products, regardless of the configuration of the starting 1,2-difluoroethylene, in a ratio of 8.8:2.0:1.2:1.2:1.0 in 85% and 92% yield for the Z- and E-olefin, respectively (Scheme 23) [48]. Interestingly, the formation of [4 + 2]-adducts in this

Discovery of antimicrobial peptides clostrisin and cellulosin from Clostridium: insights into their structures, co-localized biosynthetic gene clusters, and antibiotic activity

• Moisés Alejandro Alejo Hernandez,
• Katia Pamela Villavicencio Sánchez,
• Rosendo Sánchez Morales,
• Karla Georgina Hernández-Magro Gil,
• David Silverio Moreno-Gutiérrez,
• Eddie Guillermo Sanchez-Rueda,
• Yanet Teresa-Cruz,
• Brian Choi,
• Armando Hernández Garcia,
• Alba Romero-Rodríguez,
• Oscar Juárez,
• Siseth Martínez-Caballero,
• Mario Figueroa and
• Corina-Diana Ceapă

Beilstein J. Org. Chem. 2024, 20, 1800–1816, doi:10.3762/bjoc.20.159

• . These peptides were expressed in an E. coli host and produced in sufficient concentrations to perform bioactivity assays. The C39-associated domain was purified to facilitate the transformation from pre-peptide to the mature configuration. The mature clostrisin and cellulosin exhibited antimicrobial

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides

• Samuel M. G. Dearman,
• Xiang Li,
• Yang Li,
• Kuldip Singh and
• Alison M. Stuart

Beilstein J. Org. Chem. 2024, 20, 1785–1793, doi:10.3762/bjoc.20.157

• to a trans-configuration because of the bicyclic carbon skeleton. Trifluoroiodane 3, on the other hand, has both trans- and cis-configurations of the fluorine ligands which could play a key role in the reductive elimination step in the fluorination of phenylmagnesium bromide. Trifluoroiodane 3 also

Ugi bisamides based on pyrrolyl-β-chlorovinylaldehyde and their unusual transformations

• Alexander V. Tsygankov,
• Vladyslav O. Vereshchak,
• Tetiana O. Savluk,
• Serhiy M. Desenko,
• Valeriia V. Ananieva,
• Oleksandr V. Buravov,
• Yana I. Sakhno,
• Svitlana V. Shishkina and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2024, 20, 1773–1784, doi:10.3762/bjoc.20.156

• which the Z-configuration of the chlorovinyl fragment was detected. Post-Ugi transformations As previously mentioned [32], the introduction of the convertible 2‑bromo-6-isocyanopyridine into the Ugi bisamide structure allows the conversion of the newly formed amide into a carboxylic acid fragment after

Harnessing unprotected deactivated amines and arylglyoxals in the Ugi reaction for the synthesis of fused complex nitrogen heterocycles

• Javier Gómez-Ayuso,
• Pablo Pertejo,
• Tomás Hermosilla,
• Israel Carreira-Barral,
• Roberto Quesada and
• María García-Valverde

Beilstein J. Org. Chem. 2024, 20, 1758–1766, doi:10.3762/bjoc.20.154

• reaction took place with a α,3-like relative configuration on the major diastereomer, similar to that obtained for the Ugi/Staudinger/aza-Wittig sequence and complementary to that observed for the Ugi/reduction/cyclization sequence (see Supporting Information File 1, Figure S2). With the aim of building

• pyrrolopiperazinones when enantiopure (S)-α-methylbenzylamine was used as chiral component. In this case, although the relative configuration on C3,C4 remained unchanged ((3R*,4R*)), an equimolar mixture of diastereomers (2(1S),3R,4R) and (2(1S),3S,4S) was obtained (Scheme 7). These results indicate that these

• reactions seem to take place through conjugated additions on the enol tautomer of the Ugi adduct. Indeed, the enolate intermediate would explain the stereochemical results, controlled by the configuration in the hemiaminal intermediate and not by the chiral information on the amine, unlike in the case of

Syntheses and medicinal chemistry of spiro heterocyclic steroids

• Laura L. Romero-Hernández,
• Ana Isabel Ahuja-Casarín,
• Penélope Merino-Montiel,
• Sara Montiel-Smith,
• José Luis Vega-Báez and
• Jesús Sandoval-Ramírez

Beilstein J. Org. Chem. 2024, 20, 1713–1745, doi:10.3762/bjoc.20.152

• inhibitors of 17β-HSD3 in a microsomal fraction of rat testes. Their androgenic effect on androgen-sensitive cells LAPC-4 was also evaluated. According to the biological results, compounds 134 and 136 with substituents in (S)-configuration were better inhibitors than the (R)-isomers. Furthermore, tertiary

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• (Avantes IC-DB26-RM), which allows the proprietary software AvaSoft from Avantes to control the internal shutter of the light source via a PC. With this configuration, starting a single measurement in AvaSoft sends a TTL signal to the light source that opens the shutter, which is followed by the

• Table S2 (Supporting Information File 1). Calculated quantum yields and related quantum yields from the literature. Supporting Information Supporting Information File 4: Scripts description, configuration and supplementary data. Acknowledgements A.V. thanks J. J. van der Wal for the synthesis of

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• , unstructured configuration to AerE [113]. Otherwise, the biosynthetic machinery of aeronamide A seems to be permissive to other core sequences. Swapping the core sequence with other proteusin core structures, such as the polytheonamides core and a Rhodospirillaceae sp. proteusin precursor, demonstrated a

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• known parabens (2, 5, 6, and 11), five new ones (7–10, and 12) were identified. Their structures were elucidated by high-resolution mass spectrometry (HRMS) and 1D and 2D nuclear magnetic resonance (NMR). The configuration in 8 and 10 remained undetermined. Antimicrobial activities of compounds 2 and 5

Regio- and stereochemical stability induced by anomeric and gauche effects in difluorinated pyrrolidines

• Ana Flávia Candida Silva,
• Francisco A. Martins and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2024, 20, 1572–1579, doi:10.3762/bjoc.20.140

• conformation. Consequently the introduction of a second fluorine atom with an appropriate relative configuration was thought to reinforce and establish a predominant conformation. Theoretical levels that closely approximated the CCSD outcome included B3LYP-D3BJ/6-311++G**, B3LYP-D3BJ/DGTZVP, and ωB97XD/DGTZVP

Primary amine-catalyzed enantioselective 1,4-Michael addition reaction of pyrazolin-5-ones to α,β-unsaturated ketones

• Pooja Goyal,
• Akhil K. Dubey,
• Raghunath Chowdhury and
• Amey Wadawale

Beilstein J. Org. Chem. 2024, 20, 1518–1526, doi:10.3762/bjoc.20.136

• on a 1 mmol scale under the optimized reaction conditions (Scheme 4). The product 3aa was isolated in slightly lower yield and similar enantioselectivity compared to the 0.2 mmol scale reaction. Subsequently, we turned our attention to determine the absolute configuration of the newly formed chiral

• crystallography data of ent-3ba (Figure 2) [37]. The stereochemistry of the products in this series was assigned by analogy. Based on the observed absolute configuration of product ent-3ba and preceding literature reports [38][40], a plausible mechanistic pathway is outlined in Scheme 5. Initially, in the

Towards an asymmetric β-selective addition of azlactones to allenoates

• Behzad Nasiri,
• Ghaffar Pasdar,
• Paul Zebrowski,
• Katharina Röser,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1504–1509, doi:10.3762/bjoc.20.134

• residual water during column chromatography. Unfortunately, attempts to assign the absolute configuration of products 5 failed, as we have not been able to obtain any crystals suited for single crystal X-ray diffraction analysis. Finally, we also tested the suitability of products 5 to access acyclic α-AA

Bioinformatic prediction of the stereoselectivity of modular polyketide synthase: an update of the sequence motifs in ketoreductase domain

• Changjun Xiang,
• Shunyu Yao,
• Ruoyu Wang and
• Lihan Zhang

Beilstein J. Org. Chem. 2024, 20, 1476–1485, doi:10.3762/bjoc.20.131

• substrate contains an α-substition. Subtype 1 (A1, B1, and C1) KRs retain the original α-ᴅ-configuration, while subtype 2 (A2, B2, and C2) KRs epimerize the α-carbon to yield α-ʟ-configured products (Figure 1b). The stereocontrol of KR has been found to correlate with several conserved sequence motifs

• ] PKS cannot be accurately predicted due to the absence of both the LDD and W motifs. Moreover, KR3 of neaumycin B [14], KR19 of caniferolide A [15], KR16 of epemicin B [16], and KR26 of gargantulide B [17] show discrepancies between bioinformatic prediction and the determined product configuration

• been investigated in several DH domains, which all follow the syn-elimination mechanism [5][21][33]. Based on the product configuration, we classified DHs into two types, E-type DHs (trans-double bond) and Z-type DHs (cis-double bond) and analyzed sequence logos of the DH-associated KRs. The sequence

Rapid construction of tricyclic tetrahydrocyclopenta[4,5]pyrrolo[2,3-b]pyridine via isocyanide-based multicomponent reaction

• Xiu-Yu Chen,
• Ying Han,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2024, 20, 1436–1443, doi:10.3762/bjoc.20.126

• produced in the reaction, while the other diastereomers were not detected. In order to elucidate the relative configuration of the obtained compounds, the molecular structure of the compound 4a was determined by single crystal X-ray diffraction (Figure 1). From Figure 1, it can be seen that the fused

• that all tricyclic compounds have this kind of relative configuration on the basis of NMR spectra and single crystal structure. In order to develop the scope of the reaction, another kind of 5,6-unsubstituted 1,4-dihydropyridines 5 were also employed in the reaction, which were previously prepared from

• -position of the o-methoxyphenyl group. Therefore, compound 6g has the same relative configuration to that of the above mentioned product 3a, which also indicated that this reaction has same steric controlling effect. A plausible reaction mechanism is proposed in Scheme 1 to explain the formation of the

Computation-guided scaffold exploration of 2E,6E-1,10-trans/cis-eunicellanes

• Zining Li,
• Sana Jindani,
• Volga Kojasoy,
• Teresa Ortega,
• Erin M. Marshall,
• Khalil A. Abboud,
• Sandra Loesgen,
• Dean J. Tantillo and
• Jeffrey D. Rudolf

Beilstein J. Org. Chem. 2024, 20, 1320–1326, doi:10.3762/bjoc.20.115

• -eunicellane skeletons, respectively. Although the structures of these diterpenes only differed in their configuration at a single position, C1, they displayed distinct chemical and thermal reactivities. Here, we used a combination of quantum chemical calculations and chemical transformations to probe their

• family members in bacteria and plants [4], these diterpenoids have four main structural differences: the number and location of oxidized carbons, the absence or presence of transannular ether bridges, the configuration (cis or trans) of the bicyclic ring fusion, and the presence and configuration (E or Z

• (1) [6]. In 1, the C2–C3 and C6–C7 alkenes are E-configured, with the latter alkene configuration being conserved in all known eunicellane cyclization mechanisms. The first trans-eunicellane synthase, AlbS from the biosynthesis of albireticulone in Streptomyces albireticuli [10], was also identified

Enhancing structural diversity of terpenoids by multisubstrate terpene synthases

• Min Li and
• Hui Tao

Beilstein J. Org. Chem. 2024, 20, 959–972, doi:10.3762/bjoc.20.86

• analogues 80 and 81 with shifted double bonds were synthesized to study the stereochemistry and cyclization mechanism of casbene synthase (CS) from the castor bean (Ricinus communis), which indicated a stereochemical course in accordance with the reported absolute configuration of casbene [41] (Figure 6b