Discovery and biosynthesis of bacterial drimane-type sesquiterpenoids from Streptomyces clavuligerus

• Dongxu Zhang,
• Wenyu Du,
• Xingming Pan,
• Xiaoxu Lin,
• Fang-Ru Li,
• Qingling Wang,
• Qian Yang,
• Hui-Min Xu and
• Liao-Bin Dong

Beilstein J. Org. Chem. 2024, 20, 815–822, doi:10.3762/bjoc.20.73

• differences in 13C NMR (ΔδC = 3.3) (Figures S19–S25, Supporting Information File 1) [43]. Moreover, the key correlation observed between H5 and H7 in the ROESY spectrum provides additional support for the β-configuration of this hydroxy group (Figure S26 and Table S7 in Supporting Information File 1). These

Spatial arrangements of cyclodextrin host–guest complexes in solution studied by ¹³C NMR and molecular modelling

• Konstantin Lebedinskiy,
• Ivan Barvík,
• Zdeněk Tošner,
• Ivana Císařová,
• Jindřich Jindřich and
• Radim Hrdina

Beilstein J. Org. Chem. 2024, 20, 331–335, doi:10.3762/bjoc.20.33

• calorimetry [13]. Single crystals for many host–guest complexes have been prepared, and their structure elucidated by X-ray crystallography [14][15]. Conformations of host–guest complexes in solution have been studied by 2D NMR experiments [11] (NOESY, ROESY) or proposed computationally [16][17] based on

• proton signals of CDs in 1H NMR or 2D NMR ROESY or NOESY experiments can indicate the spatial distances between host and guest atoms and distinguish between enantiomeric guests. However, the evaluation of such interactions is often hampered by overlapping signals [20]. Results and Discussion In this work

• complex of 1 with α-CD. Interatomic distances within the host–guest complex were measured using rotating-frame nuclear Overhauser effect spectroscopy (ROESY) measurements. For the complex of 1 with α-CD, the cross-peak in the 2D ROESY spectrum between proton 5 of the glucose moiety of the host α-CD and

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• macrocycles are more shifted, with the triazole proton presenting an upfield shift from δ = 7.95 ppm to δ = 7.65 ppm and the hydroquinone protons are upfield shifted from δ = 6.77/6.67 ppm to δ = 6.60/6.58 ppm. In order to validate formation of R1 we also recorded a room-temperature H,H-ROESY NMR spectrum

Sulfur-containing spiroketals from Breynia disticha and evaluations of their anti-inflammatory effect

• Ken-ichi Nakashima,
• Naohito Abe,
• Masayoshi Oyama,
• Hiroko Murata and
• Makoto Inoue

Beilstein J. Org. Chem. 2023, 19, 1604–1614, doi:10.3762/bjoc.19.117

• ) in 1D and 2D ROE spectroscopy (ROESY) suggested that the relative configuration of the aglycone in 1 is identical to that in breynin B (6). The remaining NMR resonances (Table 2) were attributed to a tetrasaccharide based on the observation of four anomeric methine signals at δC 103.2 (C-1′), 104.5

Two new lanostanoid glycosides isolated from a Kenyan polypore Fomitopsis carnea

• Winnie Chemutai Sum,
• Sherif S. Ebada,
• Didsanutda Gonkhom,
• Cony Decock,
• Rémy Bertrand Teponno,
• Josphat Clement Matasyoh and
• Marc Stadler

Beilstein J. Org. Chem. 2023, 19, 1161–1169, doi:10.3762/bjoc.19.84

• careful comparison of the 1H and 13C NMR data with those of related compounds and ROESY correlations. The orientation of H-3 (δH 4.68, t, J = 2.8 Hz) was determined to be β based on comparing the measured and the reported coupling constants and chemical shifts for related lanostanoid derivatives [13][23

• doublet with coupling constants around 4.5 and 11 Hz [28][33]. The β-orientation of H-3 in compound 1 was further supported not only by the ROESY correlation observed between H-3 (δH 4.68, t, J = 2.8 Hz) and Me-29 (δH 0.95, s), but also by the fact that 3-epipachymic acid (3) and 3α,25S-3-O-malonyl-23

• -oxolanost-8,24(31)-dien-26-oic acid (4) were obtained during this investigation from the same extract. Some important ROESY correlations were depicted between Me-30 (δH 0.94, s) and H-17 (δH 2.14, m) as well as between H-20 (δH 2.40, td, J = 11.0, 3.5 Hz) and Me-18 (δH 0.81, s) indicating the α-orientation

Five new sesquiterpenoids from agarwood of Aquilaria sinensis

• Hong Zhou,
• Xu-Yang Li,
• Hong-Bin Fang,
• He-Zhong Jiang and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 998–1007, doi:10.3762/bjoc.19.75

• planer structure of 2 was obtained (Figure 1). The relative configuration of 2 was established by careful interpretation of the ROESY correlations (Figure 3). The ROESY correlations of H-8/H3-15 and Ha-6/H3-15 and the coupling constant of H-7 (JH-7, Ha-6 = 3.8 Hz) suggest the relative configurations (7S

• ). Thus, the planar structure of 3 was assigned (Figure 1). Further analysis of the coupling constants of H-7 (JH-7, Ha-6 = 3.3 Hz and JH-7, Hb-6 = 2.8 Hz) and the ROESY correlation (Figure 3) of H3-15/Hb-6 allowed us to conclude that H3-15 and H-7 are in the opposite orientation. Thus, the relative

• -5 and Hb-6, as well as Hb-6 and H-7, were proven by the coupling constants of Ha-6 (JH-5, Hb-6 = 12.3 Hz and JH-7, Hb-6 = 12.3 Hz), and the combined ROESY (Figure 3) correlation of H3-16/Hb-6 indicated that its relative configuration was (5R*,7R*,10R*)-4. To elucidate its absolute configuration, the

Non-peptide compounds from Kronopolites svenhedini (Verhoeff) and their antitumor and iNOS inhibitory activities

• Yuan-Nan Yuan,
• Jin-Qiang Li,
• Hong-Bin Fang,
• Shao-Jun Xing,
• Yong-Ming Yan and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 789–799, doi:10.3762/bjoc.19.59

• (δC 43.8), and H-12/C-10, C-11. The presence of a conjugated carboxylic acid was verified by the HMBC correlation of H2-2 to C-1 (δC 177.1). Concerning the geometry of 7, the ROESY correlation (Figure 2 and Figure S32 in Supporting Information File 1) of H-10/H2-12 disclosed that the ∆10,11

• (Pierce, USA) and analysis system (Bio-Rad, CA, USA) were used to visualize and detect the bands. Immunoblot densitometric analysis results were processed using ImageJ software (NIH, USA). Structures of compounds 1–9. Key 1H–1H COSY, HMBC, and ROESY correlations of compounds 1–4, 7, and 8. Calculated and

Synthesis and characterisation of new antimalarial fluorinated triazolopyrazine compounds

• Kah Yean Lum,
• Jonathan M. White,
• Daniel J. G. Johnson,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2023, 19, 107–114, doi:10.3762/bjoc.19.11

• -ray crystallographic studies and confirmed the NMR-based structure assignment. Key COSY, HMBC, and ROESY correlations, and ORTEP drawing of compound 18 are shown in Figure 1. All compounds were tested for their antimalarial activity against P. falciparum 3D7 (chloroquine-sensitive strain) and Dd2

• ), 145.0 (C-5), 146.2 (C-3); LRESIMS m/z: 392 [M + H]+, 414 [M + Na]+, 805 [2M + Na]+; HRESIMS (m/z): [M + H]+ calcd for C21H16F2N5O, 392.1317; found, 392.1317. Key HMBC, COSY and ROESY correlations, and ORTEP drawing of 18. Synthesis of ether triazolopyrazine derivatives 4–9. Synthesis of fluorinated

A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups

• Naser-Abdul Yousefi,
• Morten L. Zimmermann and
• Mikael Bols

Beilstein J. Org. Chem. 2022, 18, 1553–1559, doi:10.3762/bjoc.18.165

• and 13C NMR (800/201 MHz), COSY, HSQC, TOCSY, and ROESY (Supporting Information File 1) which gave the NMR assignments shown in Table 2 and identification of 8 as the 6A,D diol. The most significant observations in this assignment were 1) the compound is symmetric with only 3 different sugar residues

• anomeric proton (δ 5.70) could be seen to correlate to H-4 (at δ 3.80) of the A/D residues in ROESY identifying them as B/E. 4) The anomeric proton of the final residue (δ 4.73) correlated to H-4 at δ 3.92 in ROESY confirming them to be C/F. Remaining in the reaction mixture was some of the monool though

• , and ROESY (Supporting Information File 1) leading to NMR assignments shown in Table 3 and identification as the 3A,6A,D triol. The most significant observations in this assignment were 1) MS showed the compound had lost a benzyl group from the structure of 8. 2) One of the residues (A) which have an

Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library

• Sasha Hayes,
• Aya C. Taki,
• Kah Yean Lum,
• Joseph J. Byrne,
• Merrick G. Ekins,
• Robin B. Gasser and
• Rohan A. Davis

Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164

• . Chemical structures of 5-debromopurealidin H (1) and ianthesine E (2). Key COSY, HMBC and ROESY correlations for 5-debromopurealidin H (1). Chemical structures of the NatureBank bromotyrosine derivatives: psammaplysins F (3) and H (4), bastadins 4 (5), 8 (6) and 13 (7), aerothionin (8) and hexadellin A (9

Sinensiols H–J, three new lignan derivatives from Selaginella sinensis (Desv.) Spring

• Qinfeng Zhu,
• Beibei Gao,
• Qian Chen,
• Tiantian Luo,
• Guobo Xu and
• Shanggao Liao

Beilstein J. Org. Chem. 2022, 18, 1410–1415, doi:10.3762/bjoc.18.146

• ′-OCH3 (δH 3.67, s, 3H) to C-3′ indicated the methoxy group was located at C-3′. In the ROESY spectrum, the correlations of 8′-OH/H2-7 and H-8/H2-7′ (Figure 3a) suggested a trans orientation of H-8 and 8′-OH. The experimental ECD spectrum of 1 (Figure S16 in Supporting Information File 1) showed two

• , USA) at 570 nm. ʟ-NMMA was used as the positive control. Experiments were operated in triplicate. All values are described as mean ± SD of three independent experiments. Structures of compounds 1–6. Key HMBC and 1H-1H COSY correlations of 1–3. (a) Key ROESY correlations of compound 1. (b) Experimental

Glycosylated coumarins, flavonoids, lignans and phenylpropanoids from Wikstroemia nutans and their biological activities

• Meifang Wu,
• Xiangdong Su,
• Yichuang Wu,
• Yuanjing Luo,
• Ying Guo and
• Yongbo Xue

Beilstein J. Org. Chem. 2022, 18, 200–207, doi:10.3762/bjoc.18.23

• two spin-spin systems of H-3'/H-4' and H-5'/H-6' (substructure B) depicted in the 1H-1H COSY of 1. Although the direct evidence between substructures A and B was missing, to our delighted, the key ROESY correlation of H-5/H-8' (Figure 3 and Supporting Information File 1, Figure S34, recorded in DMSO

• . The ROESY spectrum (Supporting Information File 1, Figure S34, recorded in DMSO-d6) showed correlations of H-3'' and H-1'' /H-5''/HO-4'', indicating the ᴅ-configuration of glucose, while the ROESY correlations of H-1'''/H-3'''/H-5''', H-3'''/H-5''', and H-2'''/H-4''' implied the xylose should be in ᴅ

• by a ROESY correlation between H-6'' and H-1'''. Subsequently, an acid hydrolysis of 1 afforded the products including daphnogitin, a ᴅ-glucose, and a ᴅ-xylose. The absolute configurations of glucopyranosyl and xylopyranosyl was further determined by HPLC analysis of the sugar derivatives (Supporting

Tenacibactins K–M, cytotoxic siderophores from a coral-associated gliding bacterium of the genus Tenacibaculum

• Yasuhiro Igarashi,
• Yiwei Ge,
• Tao Zhou,
• Amit Raj Sharma,
• Enjuro Harunari,
• Naoya Oku and
• Agus Trianto

Beilstein J. Org. Chem. 2022, 18, 110–119, doi:10.3762/bjoc.18.12

• . The methylene carbon C35 adjacent to the hydroxamic acid group showed a smaller chemical shift (δC 28.0). The positional assignment of C34 and C35 was made by a ROESY correlation observed between H34 and 32-NH (Figure 2). To verify the structure deduced from the NMR analysis, an MS/MS analysis was

Ligand-dependent stereoselective Suzuki–Miyaura cross-coupling reactions of β-enamido triflates

• Tomáš Chvojka,
• Athanasios Markos,
• Svatava Voltrová,
• Radek Pohl and
• Petr Beier

Beilstein J. Org. Chem. 2021, 17, 2657–2662, doi:10.3762/bjoc.17.179

• 2D ROESY NMR analysis showing interaction between the alkenyl hydrogen and ortho-hydrogens on the aryl rings. Based on previously proposed mechanisms of isomerization in Suzuki cross-coupling reactions, we suggest the following explanation for the observed isomerization [25][29] (Scheme 3). In the

Nomimicins B–D, new tetronate-class polyketides from a marine-derived actinomycete of the genus Actinomadura

• Zhiwei Zhang,
• Tao Zhou,
• Taehui Yang,
• Keisuke Fukaya,
• Enjuro Harunari,
• Shun Saito,
• Katsuhisa Yamada,
• Chiaki Imada,
• Daisuke Urabe and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2194–2202, doi:10.3762/bjoc.17.141

• absolute configuration was determined by combination of NOESY/ROESY and ECD analyses. Nomimicins B, C, and D showed antimicrobial activity against Gram-positive bacteria, Kocuria rhizophila and Bacillus subtilis, with MIC values in the range of 6.5 to 12.5 μg/mL. Nomimicins B and C also displayed

• , 1 has two additional hydroxy groups at C8 and C26. The axial orientation of the C26 hydroxymethyl group was supported by the ROESY correlations H26/H6ax and H26/H10 (Figure 3). The relative configuration of the remaining part was determined to be identical with 4 on the basis of ROESY correlations

• (δH 3.99, δC 62.9) disappeared, and those for a shielded methyl group (δH 1.15, δC 13.9) appeared instead, implying that the C26 hydroxymethyl group in 1 was replaced by a methyl group in 2. HMBC correlations from H26 to C7, C8, and C9 and ROESY correlations between H26 and H10 supported the presence

Analogs of the carotane antibiotic fulvoferruginin from submerged cultures of a Thai Marasmius sp.

• Birthe Sandargo,
• Leon Kaysan,
• Rémy B. Teponno,
• Christian Richter,
• Benjarong Thongbai,
• Frank Surup and
• Marc Stadler

Beilstein J. Org. Chem. 2021, 17, 1385–1391, doi:10.3762/bjoc.17.97

• due to two methylenes at δC 38.8 (C-8) and 39.2 (C-9); three methines at δC 46.4 (C-11), 58.4 (C-6), and 77.6 (C-7) as well as two quaternary carbons at δC 45.6 (C-8) and 82.8 (C-10). Correlating 1D data with 2D NMR experiments (1H,1H COSY, 1H,13C HMBC, 1H,1H ROESY, see Figure 2) led to an underlying

• isolated and identified as fulvoferruginin (1), utilizing HRESIMS and 1D/2D NMR experiments (see Table S3 in Supporting Information File 1). The methyl group C-14 of fulvoferruginin B (2) results in an additional stereocenter at C-11. The proton at C-11 (δH 2.72) exhibited 1H,1H ROESY correlations with H-5

• (δH 4.95) and H3-13 (δH 0.99) indicating that they are on the same face of the molecule. These ROESY correlations are otherwise identical to those observed for fulvoferruginin (1). The relative stereochemistry at C-6 and C-10 was further confirmed through comparison with ROESY correlations of

α,γ-Dioxygenated amides via tandem Brook rearrangement/radical oxygenation reactions and their application to syntheses of γ-lactams

• Mikhail K. Klychnikov,
• Radek Pohl,
• Ivana Císařová and
• Ullrich Jahn

Beilstein J. Org. Chem. 2021, 17, 688–704, doi:10.3762/bjoc.17.58

• lactam 13nA (Scheme 3, insert). The relative configuration of the compounds 12m,n was determined by analogy, by ROESY investigations for the keto lactams 13m,n, and by isomerization experiments for 12n (vide infra). Amides 9o,p with cycloalkenyl substituents on the nitrogen were transformed to fused

• ROESY investigations (see Supporting Information File 1). This corresponds to the previously reported data for N-benzylacetamides [82]. It can be assumed that the amide enolates after the Brook rearrangement and the α-amide radicals (4S,S)-19i–k and (4R,S)-19i, respectively, resulting after SET

Five-component, one-pot synthesis of an electroactive rotaxane comprising a bisferrocene macrocycle

• Natalie Lagesse,
• Luca Pisciottani,
• Maxime Douarre,
• Pascale Godard,
• Brice Kauffmann,
• Vicente Martí-Centelles and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2020, 16, 1564–1571, doi:10.3762/bjoc.16.128

• , k, l, and m). Further evidence of the interlocked nature of rotaxane 1a could be obtained from the 1H,1H-ROESY NMR spectrum. Multiple through-space cross-coupling correlation between the thread and the macrocycle protons were observed between the mechanically-bonded macrocycle and the thread (Figure

• rotaxane 1a (top) and thread 4a (bottom) in CDCl3 (a designation of the signals is described in Figure 2). 1H,1H-ROESY NMR spectrum (600 MHz) of the rotaxane 1a in CDCl3. Cyclic voltammogram of ferrocene rotaxane 1a (0.67 mM) in CH2Cl2/CH3CN 1:5 (TBAPF6 0.10 M, scan rate = 10 mV/s). Single crystal X-ray

One-step route to tricyclic fused 1,2,3,4-tetrahydroisoquinoline systems via the Castagnoli–Cushman protocol

• Aleksandar Pashev,
• Nikola Burdzhiev and
• Elena Stanoeva

Beilstein J. Org. Chem. 2020, 16, 1456–1464, doi:10.3762/bjoc.16.121

• , respectively, were formed as single diastereomers (Scheme 6). The 1-ethyldihydroisoquinoline 20 showed a pronounced lower reactivity to anhydride 8, with a 30% yield of 29 as compared to 28 (71%), probably due to a steric hindrance. The relative configuration of 28 and 29 was established using 2D ROESY NMR

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• infra). The structure of the endo and exo diastereoisomers was established by ROESY experiments. In the endo isomer 9m, for example, the irradiation of the signal of proton H-4 enhanced the signals of protons H-3a and H-8b, indicating that the three protons are on the same side. In the case of the exo

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• Pro residues was not proven by HMBC, but confirmed by ROESY correlations between H-5' and H-2/H-3 to give a planar structure of 1. The chirality of the Pro residue was determined by the advanced Marfey’s method. Compound 1 was acid-hydrolyzed and the hydrolysate was derivatized with 1-fluoro-2,4

• result was consistent with the observation of a set of ROESY correlations for H-3a/H-5'b, H-5/H-5'b, and H-2''/H-6'' in the most stable conformer of (2S)-isomer 1b, which were all incompatible with any conformers of the (2R)-isomer 1a (Figure 4). Furthermore, the (2S)-configuration was supported by the

• pseudosporamicins A–C (2–4). COSY, key HMBC and ROESY correlations of pseudosporamide (1). 1H NMR ΔδS−R values for PGME amides 5a and 5b obtained from compound 1. The opposite axial chirality around the biaryl C-6–C-7'' bond influenced by the C-2 configuration in compound 1. 3D structures 1a-1 and 1b-1 are the most

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• -diastereomers (cis- and trans-10) were separated by column chromatography, and they were identified by nuclear Overhauser effect (NOE) NMR spectroscopy. In the ROESY spectrum of the cis-diastereomer (cis-10), the phenyl 1H resonances give NOE/ROE crosspeaks with the C(4)H and one of the C(5)H2 1H resonances. By

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• )bisquinolizinium 4b and 4c as photoproducts in quantitative yield. The products 4b and 4c were fully characterized by NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and ROESY) and mass spectrometry, which revealed a cyclobutane structure, specifically by the appearance of the characteristic NMR signals of the

• cyclobutane at 4.89–5.00 ppm [42][43][44][45][46]. Unfortunately, detailed 2D NMR and spectroscopic analyses did not allow a conclusive assignment of the configuration of the products. Even in the ROESY NMR spectra, only unspecific correlations were detected. However, as both products could be obtained as

Design, synthesis and investigation of water-soluble hemi-indigo photoswitches for bioapplications

• Daria V. Berdnikova

Beilstein J. Org. Chem. 2019, 15, 2822–2829, doi:10.3762/bjoc.15.275

• ROESY 2D NMR techniques. The carbon NMR signal assignments were performed by means of HSQC and HMBC 2D NMR techniques. Mass spectra (ESI) were recorded on a Finnigan LCQ Deca mass spectrometer. Elemental analysis was performed with a HEKAtech EUROEA combustion analyser by Mr. Rochus Breuer (Universität

Skeletocutins M–Q: biologically active compounds from the fruiting bodies of the basidiomycete Skeletocutis sp. collected in Africa

• Tian Cheng,
• Clara Chepkirui,
• Cony Decock,
• Josphat C. Matasyoh and
• Marc Stadler

Beilstein J. Org. Chem. 2019, 15, 2782–2789, doi:10.3762/bjoc.15.270

• . The diastereotopic protons H2-2 (δ = 3.37) showed ROESY correlations to H2-5 (δ = 2.23 ppm), but no correlations between H2-2 and H-4 (δ = 7.13 ppm) were recorded. Therefore, the configuration of the olefinic bond between C-3 and C-4 was assigned (E)-configuration. As such, the structure of 3 was

• -3 confirmed the tricarboxylic acid moiety in the molecule. COSY correlations between H2-6 and H2-5/7 confirmed the linkage of this moiety to the rest of the molecule. The absence of ROESY correlations between H-5 and H-3 but the presence of such between the protons H-3 and H2-6 indicated (Z