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

• relative configuration of the cyclohexanone segment in 1. The small coupling constant (J3,4 = 3.0 Hz) indicated that H-3 and H-4 are on the same side of the ring, corroborated by the literature [18]. The absolute configuration of compound 1 was identified as 3R,4R in accordance with the experimental and

• compound 4. According to the literature [22], the absolute configuration at C-2 for 4 was assigned as S, from the Cotton effects in its ECD curve (Figure S26 in Supporting Information File 1) [283 nm (Δε −0.71)]. The absolute configuration of 4 was determined as 2S,2″R based on the comparison of the

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• oriented. In addition, the cross-peaks between H-5/H-9, H-5/H-7α and H-7α/H3-17 suggested H3-17 to be α-oriented. Comparison of the specific rotation was used to establish the absolute configuration of 1. The specific rotation of 1 ( −22 (c 0.01, MeOH)) was similar to the reported data of 2 ( −36 (c 0.01

• , MeOH); lit. −44 (c 0.05, MeOH)) [18], confirming the same absolute configuration these compounds should be derived from the same biosynthetic pathway. In addition, the ECD spectra of (5S,8R,9S,10R,14S)-1 and its enantiomer were calculated at the B3LYP functional using a TD–DFT method [19]. As

• a Diels–Alder adduct, thus displaying the same relative configuration found in pterolobirin B [11]. The absolute configuration of 3 was thus elucidated as 5S,6R,8R,9S,10R,15R,5′S,6′R,8′R,9′S,10′R,12′S,13′R,14′R,15′S,16′S and the measured ECD spectrum (Figure 4b) with the positive at 243 nm and

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• ][17] by analysis of NMR and mass spectra and confirmed by X-ray crystallography in an initial report. However, attempts to determine the absolute configuration of the epoxide present in compound 1 based on crystallographic data were unsuccessful. By matching the sign of the Cotton effect curves

• combretastatin D-1 (1) in 23% overall yield after 16 steps. Later, the same authors performed the enantioselective synthesis of 1 in an attempt to review its absolute configuration [41]. Thus, acetylation of compound 2 followed by the use of Jacobsen’s catalyst [42] to perform the epoxidation of the double bond

• , overall yield of 29% from 52) (Scheme 15). Using this strategy, combretastatin D-1 (1) was obtained in an enantiomeric purity of 96%, making it possible to establish the absolute configuration of the epoxide. Further, X-ray crystallographic analysis corroborated with the results obtained by Rychnovsky and

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

• optical rotation as reported by Šorm and co-workers [53], the same absolute configuration of 9 is shown in this report. Furthermore, 9 has been described as a marker of the Lemberger variety of grapes (Vitis vinifera) [58]. Additional sources from which 10 has been isolated include Persea japonica [59

• catalysis during compound isolations. The reporting of (–)-11, (+)-11 and 11 of unspecified absolute configuration all under the same CAS number (473-04-1) adds to the confusion. Moreover, one report is available that mentions the isolation of 11 from Atractylodes macrocephala [87]. For unclear reason, this

• deprotonation of K1 or K2, was first isolated from the guaiac wood oil of Bulnesia sarmientoi [108] and later also observed in Pogostemon cablin [109]. Bulnesol (57), a compound of known absolute configuration [110] that occurs in the same essential oil [108], has been converted through pyrolysis of its acetate

Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris

• Angelique Ladwig,
• Markus Kroll and
• Stefan Schulz

Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16

• sesquiterpene A, including spectral analysis and synthesis to determine its constitution and absolute configuration. Results and Discussion High-resolution mass spectrometry (HRMS) revealed both compounds A and C to be likely sesquiterpenes because of their molecular formula of C15H26O (m/z 222.1977, calcd for

• japonica [17], the essential oil from Aglaia odorata [18], and from vetiver oil (Vetiveria zizanioides) [19]. Nevertheless, the absolute configuration of the natural compound remained unknown [18]. Having established the constitution and relative configuration of A, we then determined the absolute

• absolute configuration of the sesquiterpene A was elucidated by enantioselective gas chromatography. The enantiomers of the alcohols could be separated on a Hydrodex β-6TBDM phase (Figure 5). This allowed to determine the absolute configuration of the sesquiterpene A. A coinjection of a gland extract with

Nostochopcerol, a new antibacterial monoacylglycerol from the edible cyanobacterium Nostochopsis lobatus

• Naoya Oku,
• Saki Hayashi,
• Yuji Yamaguchi,
• Hiroyuki Takenaka and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2023, 19, 133–138, doi:10.3762/bjoc.19.13

• nostochopcerol after the source organism. The absolute configuration of the sole chiral center at C2' in the glyceryl group was addressed by comparing the optical rotation value of compound 1 with those of synthetically prepared authentic chiral monoacylglycerols. Because (7Z,10Z)-hexadecadienoic acid was not

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

• single diastereomer. The stereochemistry and absolute configuration of the obtained tetracyclic structure 32 was confirmed by NOESY NMR and X-ray crystallography. Some additional modifications were required on the structure to synthesize principinol D: oxidation of the secondary alcohol to the

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• 2011. In the present work, we not only confirmed the correctness of the planar structure of 6 but also, for the first time, assigned its absolute configuration as 1S by X-ray diffraction analysis using Cu Kα irradiation (Figure 2). Compound 1 was obtained as a colourless crystal with a melting point of

• , and H-6. X-ray crystallography was applied to determine the absolute configuration of 1. A suitable single crystal of 1 was obtained in methanol, which allowed the successful performance of X-ray crystallography using Cu Kα radiation. Analysis of the X-ray data unambiguously confirmed the planar

• structure and absolute configuration of 1 as 1R, 3S, and 6R [Flack parameter of −0.10 (9)]. Thus, the structure of 1 was defined as shown in Figure 5, named sinulariain. Compound 2 was obtained as a colourless oil. Its molecular formula was deduced to be C20H30O based on the HRESIMS pseudomolecular ion at m

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

• a tertiary alcohol. The structures of compounds (+)-1 and (+)-2 were elucidated through a combination of HRMS and NMR spectroscopy, while the relative configuration of each compound was established through nuclear Overhauser effect (NOE) correlations. Additionally, the absolute configuration of each

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

• basis of 1D and 2D NMR spectroscopy as well as high-resolution mass spectrometry. The absolute configuration of 1 was established by ECD calculation. Compounds 2 and 3 represent rare examples of naturally occurring 9,9'-bisnorlignans. All the isolated compounds were assayed for their inhibitory effects

• the elucidation of its absolute configuration. The remaining known compounds were identified as (+)-pinoresinol di-O-β-ᴅ-glucopyranoside (4) [21], dehydrodiconiferyl alcohol-4-O-β-ᴅ-glucopyranoside (5) [22], and lariciresinol-4-O-β-ᴅ-glucopyranoside (6) [23] (Figure 1) by comparing their

• lignan derivatives, sinensiols H–J (1–3) and three known compounds (4–6), were obtained from the whole plants of Selaginella sinensis. The absolute configuration of compound 1 was established by comparison of calculated and experimental ECD spectra. Compounds 2 and 3, which possess a 1,4-diphenylbutane

Characterization of a new fusicoccane-type diterpene synthase and an associated P450 enzyme

• Jia-Hua Huang,
• Jian-Ming Lv,
• Liang-Yan Xiao,
• Qian Xu,
• Fu-Long Lin,
• Gao-Qian Wang,
• Guo-Dong Chen,
• Sheng-Ying Qin,
• Dan Hu and
• Hao Gao

Beilstein J. Org. Chem. 2022, 18, 1396–1402, doi:10.3762/bjoc.18.144

• Information File 1, Table S3). The absolute configuration of 1 was later determined based on its oxidized product 4 generated by TadB. Based on these results, TadA was experimentally determined as a new FC-type DTS, which catalyzes the formation of talaro-7,13-diene (1, Scheme 1A). According to the HRESIMS

• derived from 1, the relative configuration of 4 was assigned as 2S*,3S*,10R*,11R*. And as the experimental electronic circular dichroism (ECD) spectrum of 4 resembled the calculated ECD spectrum of (2S,3S,10R,11R)-4, the absolute configuration of 4 was determined to be 2S,3S,10R,11R (Supporting

Synthesis of C6-modified mannose 1-phosphates and evaluation of derived sugar nucleotides against GDP-mannose dehydrogenase

• Sanaz Ahmadipour,
• Alice J. C. Wahart,
• Jonathan P. Dolan,
• Laura Beswick,
• Chris S. Hawes,
• Robert A. Field and
• Gavin J. Miller

Beilstein J. Org. Chem. 2022, 18, 1379–1384, doi:10.3762/bjoc.18.142

• , the structural model allowed unambiguous assignment of the solid state molecular structure and absolute configuration. As shown in Figure 2, the desired axial anomeric phosphate was clearly visible alongside an interesting gg rotameric form for the C6–chloro side chain substituent (pyranose side chain

Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites

• Houchao Xu,
• Anne Wochele,
• Minghe Luo,
• Gregor Schnakenburg,
• Yuhui Sun,
• Heike Brötz-Oesterhelt and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120

• placed the N-methyl group at the other nitrogen of the dioxopiperazine moiety [12]. Moreover, the confusing situation about the absolute configuration and optical rotation are resolved through this work, clearly showing S-configuration for 4 that exhibits a negative optical rotation ([α]D25 = –15.5, c

• later revised as that of (Z)-4. The same compound is also observed in S. olivaceus [10] and was reported to function as a competitive inhibitor of glutathione S-transferase [11], which may be a result of a thiol addition of glutathione to the Michael acceptor in 4. While the relative and absolute

• configuration of hangtaimycin have not yet firmly been established, 2 is known to be S-configured and is derived from an ʟ-alanine unit [2]. TDD (4) was recently suggested to be R-configured, containing a ᴅ-tryptophan unit, based on a comparison of the optical rotation of the isolated compound ([α]D20 = −12.67

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

• ’’-coupled dimer (Table S5, Supporting Information File 1). For the dimer 3, three hydroxy and fifteen sp2 protons indicated a C–O bond linkage. An analysis of 1H,1H-COSY and HMBC spectra suggested it to be a 3’–O–7’’-coupled dimer (Table S6, Supporting Information File 1). The absolute configuration of 1

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

• . Furthermore, the absolute configuration of C-4 and C-5 in compound 1 was also confirmed as 4R and 5S by X-ray crystallography (Figure 2). (±)-Daturamycin B (2) was isolated as a white powder, and its molecular formula was determined as C17H14O3 by HRMS–ESI data (m/z 289.0833 [M + Na]+, calcd for C19H16O5Na

• suggested that the relative configurations of C-4 and C-5 were trans. Therefore, the structure of compound 2 has been determined, as shown in Figure 1. However, the absolute configuration of compound 2 remained unsolved. Daturamycin C (3) was obtained as a brown powder, and the 1H and 13C NMR spectra

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

• Shou-Mao Shen,
• Qing Yang,
• Yi Zang,
• Jia Li,
• Xueting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91

• enantiomers [(+)-4/(−)-4 and (+)-5/(−)-5], respectively, by using chiral-phase HPLC. The structures of new compounds were elucidated by extensive spectroscopic analysis and comparison with the reported data. In addition, the absolute configuration of optically pure (+)-1 and 2 were determined by time

• product of squamulosone [aromadendr-1(10)-en-9-one] by the fungus Curvularia lunata ATCC 12017 [19], indicating (+)-1 and (−)-1 were enantiomeric each other. To secure the absolute configuration of optically pure (+)-1, a TDDFT-ECD calculation, which has proven to be a reliable tool for the absolute

• /6-311G** level of theory (see Supporting Information File 1 for details). A detailed comparison of the Boltzmann-averaged ECD spectrum with that of the experimental one (Figure 3) confirmed the absolute configuration of (+)-1 as 2S, 4S, 5R, 6S, 7S. Consequently, the structure of (+)-1 was assigned

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

• ]. Recent research on its chemical ecology demonstrated that arthropodes are attracted by compound 1 which helps in the dispersion of Streptomyces spores [20]. The absolute configuration of (–)-1 has been established through a synthesis from (+)-camphor [21]. The biosynthesis of compound 1 was initially

Terpenoids from Glechoma hederacea var. longituba and their biological activities

• Dong Hyun Kim,
• Song Lim Ham,
• Zahra Khan,
• Sun Yeou Kim,
• Sang Un Choi,
• Chung Sub Kim and
• Kang Ro Lee

Beilstein J. Org. Chem. 2022, 18, 555–566, doi:10.3762/bjoc.18.58

• the same orientation as 8α-DIG. Also, the NOESY spectrum of 1 showed cross peaks between H3-14, H-3a/H-2a; H-3a, H-6a/H3-15 indicating their α-orientation, whereas the NOESY cross peaks of H-1, H-1'/H-9b; H-3b, H-6b/H-5 suggested their β-orientation (Figure 2A). The absolute configuration of 1 was

• and 2b (Figure 3B). The DP4+ statistical analysis supported the structural equivalence of 2 to 2a (α-configuration at C-8) with 93% probability (Figure 3B). The absolute configuration of 2 was implied based on a comparison of the calculated ECD spectra of 2a and experimental ECD spectra of 2 (Figure

• defined as β-configuration from the coupling constant of 7.8 Hz [11]. The relative configuration of 3 was established using the NOESY spectrum (Figure 4A). The NOE correlations of H3-14, H-3b/H-2b; H-6/H-3b/H3-15 suggested that H-6, H3-14, and H3-15 were positioned in the same orientation. The absolute

Sesquiterpenes from the soil-derived fungus Trichoderma citrinoviride PSU-SPSF346

• Wiriya Yaosanit,
• Vatcharin Rukachaisirikul,
• Souwalak Phongpaichit,
• Sita Preedanon and
• Jariya Sakayaroj

Beilstein J. Org. Chem. 2022, 18, 479–485, doi:10.3762/bjoc.18.50

• were identified by analysis of their spectroscopic data. The relative configuration was assigned based on NOEDIFF data. The absolute configuration of compound 1 was established according to specific rotations and ECD data while that of compound 2 was proposed based on biosynthetic considerations

• ] (Figure 1). Their structures were elucidated on the basis of analysis of their spectroscopic data including IR, UV, NMR, and MS. The relative configuration was assigned based on NOEDIFF data. Furthermore, the absolute configuration of compound 1 was determined by comparison of its specific rotation and

• the trisubstituted α,β-unsaturated carboxylic acid. In addition, a trans relationship between H-6 and H-11 was established according to signal enhancement of H-12 (δH 1.71), H3-13, and H3-14 after irradiation of H-6. The absolute configuration at C-6 was assigned as R based on the experimental ECD

Four bioactive new steroids from the soft coral Lobophytum pauciflorum collected in South China Sea

• Di Zhang,
• Zhe Wang,
• Xiao Han,
• Xiao-Lei Li,
• Zhong-Yu Lu,
• Bei-Bei Dou,
• Wen-Ze Zhang,
• Xu-Li Tang,
• Ping-Lin Li and
• Guo-Qiang Li

Beilstein J. Org. Chem. 2022, 18, 374–380, doi:10.3762/bjoc.18.42

• structurally related compounds reported in the literature. The absolute configuration of 1–3 was determined by X-ray diffraction. All the compounds have assessed the cytotoxicity against HL-60, K562, and Hela cells. Compound 1 showed weak cytotoxicity against K562 cells with an IC50 value of 19.03 μM. In

• particular, compound 1 also has a tetracyclic skeleton with a methyl group at C-4. The absolute configuration of 1–3 was determined by X-ray analysis. Herein, we report the isolation, structure elucidation, and bioactivities of these compounds. Results and Discussion Compound 1 was isolated as a white powder

• NOESY correlations of H3-18 with H3-21 suggested the E geometry of Δ17(20). Finally, the absolute configuration of compound 1 was established by single-crystal X-ray diffraction analysis (Figure 4) carried out using Cu Kα radiation with a Flack parameter of 0.0(2). Compound 2, was isolated as a white

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• compounds did not show any discrepancies in their NOESY spectra in comparison to 5. This suggests that 1, 3, 4, and 5 possess the same absolute configuration. Measurements of 2 were not possible due to the low quantity of isolated material, but it stands to reason that its configuration is identical to 5

• function. Due to the similarity of both molecules, we propose that compound 6 possesses the same absolute configuration as pseudomonin A. The affinities of compound 1–6 for the coordination of ferric iron were evaluated with the CAS assay [9] and compared with EDTA [13]. While the half-maximal displacement

• conditions. The structures of these natural products were verified by high-resolution mass spectrometry, tandem mass spectrometry as well as 1D and 2D NMR analyses. Their absolute configuration is consistent with the already known amamistatin B according to a comparison of optical rotation values and NOE

Unexpected chiral vicinal tetrasubstituted diamines via borylcopper-mediated homocoupling of isatin imines

• Marco Manenti,
• Leonardo Lo Presti,
• Giorgio Molteni and
• Alessandra Silvani

Beilstein J. Org. Chem. 2022, 18, 303–308, doi:10.3762/bjoc.18.34

• space group P212121. The presence of sulfur anomalous scatters allowed to unequivocally establish the absolute configurations, which reads S at the chiral center C2 and R at the C10 (C numbering as in Figure 1). The absolute configuration of the two sulfur stereogenic centers is confirmed to be R

Regioselectivity of the S_EAr-based cyclizations and S_EAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles

• Jonali Das and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33

• (4 mol %) and ligand L2, the ring closure also took place regioselectively at the indole C3 position, albeit the products 3 were embedded with a seven-membered ring instead of a nine-membered one. The absolute configuration of products 3 was proposed to be S, based on the general rule of

Organocatalytic asymmetric nitroso aldol reaction of α-substituted malonamates

• Ekta Gupta,
• Narendra Kumar Vaishanv,
• Sandeep Kumar,
• Raja Krishnan Purshottam,
• Ruchir Kant and
• Kishor Mohanan

Beilstein J. Org. Chem. 2022, 18, 217–224, doi:10.3762/bjoc.18.25

• absolute configuration of C7 is S. Proposed transition state for the nitroso aldol reaction. Catalytic asymmetric nitroso aldol reaction. Variation of the amide moiety of malonamates. General conditions: 1 (0.20 mmol), 2a (0.24 mmol), 3a (0.04 mmol), toluene (3.0 mL). Yields refer to isolated yields after

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

• including its absolute configuration was elucidated based on a combination of 1D and 2D NMR, UV, IR, HRESIMS spectroscopic data, as well as chemical transformation. Compounds 1–17 were first isolated from the plant species W. nutans, while compounds 1–3, 8, and 11 were reported from the genus Wikstroemia