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Search for "configuration" in Full Text gives 1055 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Kinetic resolution of racemic planar-chiral vinylcymantrenes by molybdenum-catalyzed asymmetric metathesis dimerization
Beilstein J. Org. Chem. 2026, 22, 568–574, doi:10.3762/bjoc.22.42
- configuration of (–)-2b Levorotatory AMD/KR product (–)-2b, which was obtained as in entry 8, Table 1 using Mo/(R)-L1 precatalyst, was recrystallized by slow diffusion of pentane into the concentrated diethyl ether solution. Crystals of (–)-2b were grown as light-yellow blocks. The X-ray crystallography
- Information File 2 for details). The two cyclopentadienides and the olefinic moiety are nearly coplanar with a C2–C13–C14–C8 torsion angle of 175.4(2)°. The Flack parameter for this structure was determined to be –0.010(4), and the absolute configuration of (–)-2b was unambiguously determined to be (S,S) (see
Experimental and DFT studies on the regioselective methanolysis of 5-azido-9-oxabicyclo[6.1.0]nonan-4-yl 4-nitrobenzoate isomers
Beilstein J. Org. Chem. 2026, 22, 547–556, doi:10.3762/bjoc.22.40
- -ray analysis (Figure 2) [25]. X-ray analysis of azido compound 10 confirmed the trans configuration of the azide group with chloride and the cis configuration with the acetate. Our suggested mechanism for the ring-opening of the epoxides 9 with HCl(g) in MeOH proceeded as described in Scheme 3. As
- spectroscopic data. However, the uncertainty or weakness of the cross peaks in NOESY and NOE signals indicated that compound 11 exhibits significant conformational flexibility. The cyclooctane ring has increased flexibility, so the configuration assignment of 11 is difficult to determine with the help of the
Melifoliox B, a novel phloroglucin derivative isolated from Melicope barbigera (Rutaceae) and synthesis of new oxidation products from melifoliones A and B
Beilstein J. Org. Chem. 2026, 22, 535–546, doi:10.3762/bjoc.22.39
- hydrogenated pyran rings of 4 can only be linked cis, the two possible enantiomers of 4 have the following configuration: (6aR,9S,10aS,10bR) or (6aS,9R,10aR,10bS). Due to the finding, that the isolated compound showed no optical rotation, it exists as a racemate. A stereo model of 4 provided important
Modern synthetic pathways towards eribulin and its subunits
Beilstein J. Org. Chem. 2026, 22, 495–526, doi:10.3762/bjoc.22.37
- . Here, 121 bears the right configuration needed for Halaven synthesis, but the authors also showed that 122 was easily converted to 121 via Mitsunobu inversion. Although 121 only represents a small building block for the total assembly of 1, this method especially stands out for its cost-efficiency and
Recent advances in the stereoselective synthesis of distal biaxially chiral molecules
Beilstein J. Org. Chem. 2026, 22, 461–479, doi:10.3762/bjoc.22.34
- –C derivatives through reaction of 1-alkynylnaphthalenes with benzamides. In this context they observed that the stereoselectivity of the alkyne insertion could be tuned by solvent effects, particularly with hexafluoroisopropanol, which induced inversion of the C–C axial configuration (not shown). In
Electrosynthetic access to unsymmetrical oxaza[8]helicenes with high chiral stability and strong circularly polarized luminescence (CPL)
Beilstein J. Org. Chem. 2026, 22, 372–382, doi:10.3762/bjoc.22.25
- emitters. The |glum| values were determined to be 0.001 at 498.0 nm for 5a, 0.0026 at 474.5 nm for 5b, 0.0006 at 441.8 nm for 6a, and 0.0018 at 448.8 nm for 6b, with the (P)-configuration exhibiting a positive Cotton effect and the (M)-configuration showing a negative Cotton effect (Figure 5B). According
- lowest energy excited state (S1) and TD-DFT calculated transitions at MN15/6-311G(2d,p)/SMD=chloroform level of theory. Chiroptical properties of oxaza[n]helicenes: (A) CD spectra measured in chloroform (1 × 10−5 M); CPL spectra measured in chloroform (1 × 10−3 M). Solid lines for (M)-configuration and
- dashed lines for (P)-configuration of 5a (black), 5b (blue), 6a (green), and 6b (red). Recent examples of hetero[8]helicenes: (A) symmetric hetero[8]helicenes; (B) unsymmetrical hetero[8]helicenes; (C) short-step electrosynthetic access to new unsymmetrical oxaza[8]helicenes. Short-step synthesis of
Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis
Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21
- isomers (128b) of the aldol addition is privileged to undergo intramolecular esterification to give alstoscholarinoid B (125). The configuration of the other isomer 128c has been reportedly isolated already in 2002 by Kuo and Chiang [182]. For alstoscholarinoid A (124) an analogous oxidative cleavage and
Spirobarbiturates with a pyrrolizidine moiety: synthesis, structure and biological evaluation
Beilstein J. Org. Chem. 2026, 22, 274–288, doi:10.3762/bjoc.22.20
- in the maleimide: in most cases the endo-isomer is the main (or only) product, but for some N-arylmaleimides the exo-product is predominant. The proposed mechanism is discussed, and the products were characterized by detailed spectral analysis. The configuration of the stereocenters was determined by
- configuration of their stereocenters, was determined using NMR spectroscopy and XRD analysis. endo-Isomers 4a–e exhibited the following characteristic signals in their 1H NMR spectra: multiplets in the range of δ 1.5–4.4 ppm were assigned to the protons of the pyrrolizidine ring system. The methyl singlets of
- allowed unambiguous determination of the absolute configuration of the spirobarbiturate adducts. Additionally, a detailed analysis of intermolecular interactions in the crystal structure was performed using Hirshfeld surface calculations, providing valuable insights into the packing arrangements of these
Arene activation via π-bond localization: concepts and opportunities
Beilstein J. Org. Chem. 2026, 22, 257–273, doi:10.3762/bjoc.22.19
- of the archetypal pentaammineosmium(II) system prior to discussing synthetic utility (Figure 6). The five ammine ligands, strong σ-donors with negligible π-interaction, combined with the d6 configuration render the Os(II) center highly electron-rich and an exceptional π-base [43]. This electronic
- configuration promotes strong binding to π-acidic ligands, effectively compensating for the loss of aromaticity upon η2-coordination to arenes, while disfavoring oxidative addition due to geometric constraints of the octahedral complex. The resulting η2-arene complexes, encompassing both arenes and heteroarenes
- metal center with α-pinene and subsequent ligand substitution proceeds with retention of configuration, the corresponding Mo(0) complex undergoes racemization during substitution (Scheme 2A). This obstacle was overcome by a redox-based approach: oxidation of the Mo(0)–α-pinene complex with iodine to a
Configuration–packing synergy enabling integrated crystalline-state RTP and amorphous-state TADF
Beilstein J. Org. Chem. 2026, 22, 224–236, doi:10.3762/bjoc.22.16
- single molecule under different environments or phases are still relatively rare [33]. The underlying challenge lies in the different demands that RTP and TADF place on the microscopic configuration and solid-state environment. RTP typically favors molecular rigidity, confinement, and specific
- configuration design and material-scale packing/confinement engineering to enable the controlled switching between RTP and TADF. Among the potential receptor units, imide, with its strong electron-withdrawing nature and prominent n→π* contribution from the two carbonyl groups, offers a dual advantage: it
- facilitating thermally activated reverse intersystem crossing (RISC) and enabling TADF. Therefore, a molecular platform based on imide is expected to achieve programmable triplet management through a “configuration-decoupling + packing/confinement synergy” strategy. This platform can enable the selective
Screwing the helical chirality through terminal peri-functionalization
Beilstein J. Org. Chem. 2026, 22, 205–212, doi:10.3762/bjoc.22.14
- phosphine oxide and the nitro-functionalized oxa[5]helicene. This ion-pairing interaction was also studied using NMR titration and Job’s plot analysis. The transition state depicted in Figure 3 was found to be most favorable providing the product with M-configuration. Looking ahead, these strategies may
Streptoquinolines A and B, new antibacterial meroterpenoids produced by Streptomyces sp. TMPU-A0679
Beilstein J. Org. Chem. 2026, 22, 185–191, doi:10.3762/bjoc.22.12
- between C-11 and C-1'. Consequently, the planar structure of compound 1 was elucidated as shown in Figure 1, consistent with the molecular formula and degree of unsaturation. The relative configuration of compound 1 was elucidated based on ROESY correlations, as shown in Figure 3. Clear ROESY cross-peaks
- between H3-14 and H3-15, suggested that these protons resided on the opposite face. These results support a relative configuration of 5R*, 8S*, 9S*, and 10R* for the drimane skeleton of compound 1. However, it was not possible to elucidate the configuration at C-4' from available NMR data
- 1H,1H COSY and HMBC correlations as those observed for 1 (Figure 2), confirming that compound 2 shared the same planar structure. The specific rotations of 1 and 2 were similar in both sign and magnitude, suggesting that they shared the same absolute configuration for most chiral centers. However, a
Asymmetric Mannich reaction of aromatic imines with malonates in the presence of multifunctional catalysts
Beilstein J. Org. Chem. 2026, 22, 151–157, doi:10.3762/bjoc.22.8
- of the iodine atom cannot be excluded in the emergence of the stereoselectivity. To determine the absolute configuration of product 3 the nitrogen atom was additionally protected with Boc2O followed by the removal of the pyridinesulfonyl group with Mg in MeOH (see Supporting Information File 1) [28
- ]. Although basic conditions caused partial racemization during the protection or deprotection step, the Boc-protected amine was obtained in low enantiomeric purity. Chiral HPLC analysis and comparison with an authentic sample revealed the S-configuration of the Mannich adduct [29]. Absolute configurations of
- catalyst and the imine and malonate attacks from si-face affording the product in S-configuration (Figure 2). To demonstrate the utility of the elaborated catalytic system, the Mannich reaction between aromatic imines, both with electron-withdrawing and electron-donating substituents in the phenyl ring
Highly electrophilic, gem- and spiro-activated trichloromethylnitrocyclopropanes: synthesis and structure
Beilstein J. Org. Chem. 2026, 22, 123–130, doi:10.3762/bjoc.22.5
- . Conditions for obtaining the target cyclopropanes were optimized. The process is characterized by high diastereoselectivity and allows obtaining cyclopropanes with trans-configuration of -NO2 and -CCl3 groups. Monocyclic (based on malonic acid dinitrile, methyl cyanoacetate, ethyl cyanoacetate
- and 9b (1.3:1 dr, according to the 1H NMR spectrum) due to the axial chirality of this molecule. The mixture was easily separated by silica gel column chromatography. Each of the isomers is characterized by the trans-configuration of the nitro- and trichloromethyl groups in the cyclopropane ring (3JH
- to the bromonitroalkene afford the intermediate anion II, followed by tautomerization and formation of anion IV, which undergoes intramolecular nucleophilic substitution of the bromide along the C-alkylation pathway [37][38][39] (Scheme 6). The trans-configuration of the methine protons of the
Total synthesis of natural products based on hydrogenation of aromatic rings
Beilstein J. Org. Chem. 2026, 22, 88–122, doi:10.3762/bjoc.22.4
- diastereoselective hydrogenation of symmetrical 2,5-DKP (2,5-dipiperazinone) 67 using a rhodium complex (Scheme 8) [63]. The saturated pentacyclic compound 68 was obtained in high yield and excellent diastereoselectivity. The hydrogen atoms in the final product were all arranged in cis configuration. Key features of
Total synthesis of asperdinones B, C, D, E and terezine D
Beilstein J. Org. Chem. 2025, 21, 2730–2738, doi:10.3762/bjoc.21.210
- gene clusters that code for a (3R) configuration. Keywords: C–H activation; indole alkaloid; Negishi reaction; prenylation; Introduction Alkaloids constitute an important family of naturally occurring compounds with a rich history in the annals of bioactive compounds [1]. Among these, the family of
- Bock in 1987 [16]. It is of interest that although the biosynthesis of 3-indolylbenzoquinone-2,5-dione ent-5 is initiated with ʟ-tryptophan and anthranilic acid [17], the resulting natural products 1–4 possess a (3R) configuration. This is because of an epimerization mediated by the non-ribosomal
Competitive cyclization of ethyl trifluoroacetoacetate and methyl ketones with 1,3-diamino-2-propanol into hydrogenated oxazolo- and pyrimido-condensed pyridones
Beilstein J. Org. Chem. 2025, 21, 2716–2729, doi:10.3762/bjoc.21.209
- configuration of other diastereomers (Figure 2 and Figure 3). Analysis of the XRD results shows that the formation of bicyclic compounds are formed with two types of ring fusion: trans- and cis-type, similar to the structure of decalin [68]. In all studied structures 4аcc, 4аct, 4аtt, 4аtc, 4dct, 5ctc, 5ctt
- substituent R at the bridgehead carbon atom can occupy only an axial position with respect to both cycles. On the other hand, the CF3 group is a conformational anchor and always occupies a pseudo-equatorial position, which is why it leads to the trans-configuration of the piperidone cycle. In the cis-junction
- -configuration of the piperidone ring. At the same time, in relation to the hexahydropyrimidine ring, the bridgehead substituent R occupies a pseudo-axial position. The relative configuration of the hexahydropyrimidine ring in compounds 4 is determined by the pseudo-axial (trans) or equatorial (cis) position of
Recent advancements in the synthesis of Veratrum alkaloids
Beilstein J. Org. Chem. 2025, 21, 2657–2693, doi:10.3762/bjoc.21.206
- trans-fusion of the A,B-rings and the configuration of the methyl group at C25, among other features [13]. Like the related subclasses, cevanine-type alkaloids exhibit toxicity in humans by acting on the sodium channels of nerve cells. Increased stimulation, associated with the vagal nerve results in a
- introduced by addition of 2-lithio-5-methylpyridine (94) to methyl ketone 93, with the major addition product 95 exhibiting the desired configuration at C20. Tosylation of the primary C18–OH in 95 (and secondary C3–OH) was followed by intramolecular nucleophilic substitution through the pyridine nitrogen
- . The pyridinium species was reduced to reveal the piperidine E-ring with correct configuration of the stereocenters at C22 and C25. Reduction of the C3-tosylate afforded deoxoverticinone (96), a known congener of verticine. Seven more redox manipulation steps were required to install the C6–OH group
Chemoenzymatic synthesis of the cardenolide rhodexin A and its aglycone sarmentogenin
Beilstein J. Org. Chem. 2025, 21, 2637–2644, doi:10.3762/bjoc.21.204
- -electron demand Diels–Alder (IEDDA) reaction was utilized to successfully construct the BCD tricyclic structure with the correct configuration of the four contiguous stereocenters in just one step. However, the requirement of a series of protecting group manipulations undermined the step-economy and
Recent advances in total synthesis of illisimonin A
Beilstein J. Org. Chem. 2025, 21, 2571–2583, doi:10.3762/bjoc.21.199
- as “illisimonane skeleton”. The absolute configuration of (−)-illisimonin A was determined to be 1R,4R,5R,6R,7S,9S,10S by comparing the calculated electronic circular dichroism (EDC) spectrum with experimental CD data (Figure 2). Biological evaluation revealed that illisimonin A exhibits
- Rychnovsky [28], Kalesse [29], Yang [30], Dai [31] and Lu [32] have achieved the total synthesis of this molecule. Notable, Rychnovsky and co-workers revised the absolute configuration of (−)-illisimonin A to 1S,4S,5S,6S,7R,9R,10R. This review summarizes the reported synthetic routes toward illisimonin A
- , including uncompleted approaches. Review Rychnovsky’s synthesis and the absolute configuration revision of (−)-illisimonin A In 2019, Rychnovsky’s group reported the first total synthesis of illisimonin A [28]. Recognizing that the strained trans-pentalene moiety in the molecule is challenging to construct
Total syntheses of highly oxidative Ryania diterpenoids facilitated by innovations in synthetic strategies
Beilstein J. Org. Chem. 2025, 21, 2553–2570, doi:10.3762/bjoc.21.198
- limitations in technical capabilities at the time, its absolute configuration remained undetermined. Over the subsequent two decades, its hydrolysis product ryanodol (4) and several structurally related analogs were isolated sequentially [9][10][11][12][13][14]. The absolute configurations of both 1 and 4
- the correct structure of ryanodol to be 3-epi-ryanodol (5), thereby revising the previously accepted configuration [15]. Since then, numerous analogs based on the ryanodol scaffold have been identified and characterized. As of now, 18 natural products from this family have been successfully isolated
- the correct relative configuration undergoes hydrolysis of its spirocyclic lactone moiety under basic conditions to yield 13, establishing the critical C5 chiral center. Under acidic conditions, intermediate 13 undergoes ketal deprotection followed by successive intramolecular aldol reactions
Rapid access to the core of malayamycin A by intramolecular dipolar cycloaddition
Beilstein J. Org. Chem. 2025, 21, 2542–2547, doi:10.3762/bjoc.21.196
- undesired stereochemistry at C3 due to a possible chair-like transition state like 10a (Scheme 2B). This phenomenon is consistent with the observations from previous syntheses [31][35][36]. We anticipated that late-stage epimerization might invert the configuration once the acyl group is revealed at the C2
- nitrile oxide. At this stage, it is not clear that the diastereomeric ratio (dr 4:1) may share with the same configuration at the C2 or C2’ position. The mixture of 18 was subjected to reduction of the imine motif by NaBH3CN in AcOH–MeOH and immediately protected with the Boc group. The isolated yield of
- from the INOC cycloaddition can be converted to a single stereoisomer of 20. With all required stereogenic centers embedded in the 6-5 trans-fused bicyclic skeleton, the remaining problem is converting C to O to install the secondary alcohol at C2 with retention of the β-configuration. The programmed
Effect of a photoswitchable rotaxane on membrane permeabilization across lipid compositions
Beilstein J. Org. Chem. 2025, 21, 2498–2512, doi:10.3762/bjoc.21.192
- the macrocycle, and is consistent with the higher dye release observed for 1-E compared to 1-Z in EYPC/Chol 8:2 LUVs. By contrast, the azobenzene configuration has little effect in the more rigid EYPC/Chol 6:4 bilayers. In highly fluid pure EYPC bilayers, however, the rapid release within the first
- bilayer, which is influenced by azobenzene isomerization. However, in the highly disordered EYPC membranes, the macrocycle appears to retain sufficient mobility regardless of the azobenzene configuration, enabling it to reach the lipid–water interface and trigger membrane permeabilization in both isomeric
The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions
Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184
- purification techniques [62][63][64]. Synthesis of pyrrolo-isoxazolidines utilizing nitrosoarenes via the multicomponent strategy is indeed feasible [65][66]. In a similar manner, Chakraborty obtained diastereomer products, primarily in cis configuration, from the cycloaddition reaction of a fluoro or a furyl
- aromatic aldehydes exhibit a Z-configuration [112][113] and it appears that endo-coupling of the Z-configured C,N-diphenylnitrone with maleimide is more favorable. Indeed, the distribution of the cis/trans product is also found to be significantly influenced by the nature of the substituents present in the
Synthetic study toward vibralactone
Beilstein J. Org. Chem. 2025, 21, 2376–2382, doi:10.3762/bjoc.21.182
- lactone 13 through allylic oxidation and cross metathesis. For the construction of the cyclopentene ring, an alkylidene carbene-mediated C–H insertion would be applied [35]. The synthetic route could be traced back to β-lactone 14, which contains two continuous stereogenic centers with trans configuration
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