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Search for "ACID" in Full Text gives 3066 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
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
- compound 19. This intermediate is converted to lactone 20 via base-promoted Grob fragmentation followed by acid-mediated MOM deprotection. Epoxidation of the C10–C11 double bond in 20, lactone hydrolysis-promoted epoxide ring opening, and inversion of the C10 hydroxy configuration, yield the key
- secondary hydroxy group, successfully achieving the conversion of ryanodol (4) to 3-epi-ryanodol (5) and 3-epi-ryanodine (30) [45]. The specific synthetic route is as follows (Scheme 3): Beginning with ryanodol (4), an acid-promoted fragmentation yields anhydroryanodol (10). Subjecting compound 10 to Li/NH3
- natural product. Similarly, starting from 57, installation of an allyl group at C2, followed by oxidative cleavage, reduction, and deprotection, provided cinncassiol B (7). Subjecting this compound to an acid-promoted fragmentation reaction then completed the total synthesis of cinncassiol A (9
Ni-promoted reductive cyclization cascade enables a total synthesis of (+)-aglacin B
Beilstein J. Org. Chem. 2025, 21, 2548–2552, doi:10.3762/bjoc.21.197
- ] by flash column chromatography in 30% yield. The stereocontrolled formation of aryltetralin 13 could be attributed to an adoption of a pseudo-half-chair conformation 5a. Finally, the final step towards the total synthesis of (+)-aglacin B (2) was achieved by treatment with BF3·Et2O as the Lewis acid
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
- 19 was moderate because the anomeric carbon at C7 is associated with an acid-sensitive acetonide group. The structural determination of the major product 19a was accomplished by comprehensive NMR spectroscopy and further unambiguously confirmed by X-ray analysis (see Supporting Information File 1 for
Synthesis and characterization of a isothiouronium-calix[4]arene derivative: self-assembly and anticancer activity
Beilstein J. Org. Chem. 2025, 21, 2535–2541, doi:10.3762/bjoc.21.195
- chains were tethered to the calixarene hydroxy groups (lower rim) by reaction with dodecyl iodide in the presence of NaH. At the upper rim of this derivative, four formyl groups were introduced by reaction with hexamethylenetetramine in trifluoroacetic acid. The formyl groups were reduced to alcohol
Isoorotamide-based peptide nucleic acid nucleobases with extended linkers aimed at distal base recognition of adenosine in double helical RNA
Beilstein J. Org. Chem. 2025, 21, 2513–2523, doi:10.3762/bjoc.21.193
- acid (RNA) impacts many biological processes; however, the complexities of its many roles are not completely understood. Therefore, designing tools for molecular recognition is of paramount importance. Peptide nucleic acids (PNA) show promise as a tool for selective recognition of double helical
- oligonucleotides (TFOs) [8]. TFOs are utilized in both RNA and DNA recognition [9][10][11][12] and a particular type of TFO, peptide nucleic acid (PNA), has emerged as a promising probe for recognizing ncRNA [13][14][15][16]. The Nielsen lab first designed PNA with the N-(2-aminoethyl)glycine backbone for the
- functionalized. We noted that isoorotic acid offered an opportune core from which to prepare extended nucleobase monomers through amide bond formation (Figure 3a) [34]. Secondly, the work began with the initial goal to find an extended nucleobase scaffold capable of strong binding to A and then reverse its point
Assembly strategy for thieno[3,2-b]thiophenes via a disulfide intermediate derived from 3-nitrothiophene-2,5-dicarboxylate
Beilstein J. Org. Chem. 2025, 21, 2489–2497, doi:10.3762/bjoc.21.191
- formation of carboxylic acid 9bA, isolated in 71% yield (Scheme 7). In addition, an attempt to cyclize 6b in the presence of DBU without a solvent at 110 °C led to significant destruction of the substrate and product 9b was obtained with a yield of about 20%. Cyclization of substrate 4a with NaH in toluene
Ex-situ generation of gaseous nitriles in two-chamber glassware for facile haloacetimidate synthesis
Beilstein J. Org. Chem. 2025, 21, 2465–2469, doi:10.3762/bjoc.21.188
- was the p-methoxy derivative 11 which, as expected, was more reactive and hence more difficult to purify due to decomposition on silica gel. The p-methoxybenzyl trifluoroacetimidate (9) has been shown to be an effective regent for the acid-catalyzed benzylation of alcohols [12][30]. Conclusion In
The intramolecular stabilizing effects of O-benzoyl substituents as a driving force of the acid-promoted pyranoside-into-furanoside rearrangement
Beilstein J. Org. Chem. 2025, 21, 2456–2464, doi:10.3762/bjoc.21.187
- (Figure 1) [19]. The introduction of an alkyl or aryl substituent in the anomeric center prevents free interconversion between pyranose and furanose forms; however, this transformation can still occur under specific conditions, typically in the presence of an acid catalyst. Even under such conditions, the
- furanose form through steric and electrostatic effects. In our previous work [24], we investigated the energetic aspects of the pyranoside-into-furanoside (PIF) rearrangement that proceeded under acid-promoted sulfation and whose mechanism was studied by us previously [25] along with the mechanism of
- , transformation of galactopyranosides to galactofuranosides under the action of TsOH in methanol [29] and silica-supported perchloric acid [30] is known. However, in both these cases di-O-isopropylidene ketals were used that underwent removal upon the isomerization leading to the loss of the aglycon. Recently, we
Catalytic enantioselective synthesis of selenium-containing atropisomers via C–Se bond formations
Beilstein J. Org. Chem. 2025, 21, 2447–2455, doi:10.3762/bjoc.21.186
- wall and bottom of the lead chamber when roasting pyrite to produce sulfuric acid. After analysis, it was confirmed that there was a new element in it. Referring to the name of tellurium (originally meaning earth), he named it selenium according to the word "Selene" in ancient Greek mythology [2
- VQM intermediate Int 9 and benzenesulfonic acid. Finally, benzenesulfonic acid further reacts with the VQM intermediate to afford product 9, concomitant with regeneration of the catalyst. This protocol provides a promising approach for the enantioselective synthesis of axially chiral styrenes
- (Scheme 4). In 2025, Yang, Lu, and co-workers employed bifunctional catalysts, including chiral thiourea derivatives or chiral phosphoric acid, to activate alkynes and selenols through multiple hydrogen-bonding interactions, thereby achieving an enantioselective hydroselenation of alkynes [22]. All
Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds
Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185
- , terpenoids, alkaloids, steroids and carbanucleosides. The spectrum of biological activities of the listed classes is wide and unique in efficacy. Natural prostaglandins are polyoxygenated derivatives of a hypothetical twenty-atom prostanoic acid, the C8–C12 atoms of which are contained in a cyclopentane ring
- . as a method for ring contraction of the cyclohexene ring to produce cytostatic taiwaniaquinoids [13][14][15]. Compound 4, derived from (–)-abietic acid, was subjected to an oxidative cleavage reaction to produce ketoaldehyde 5. Subsequent intramolecular aldol cyclization using 1,8-diazobicyclo[5.4.0
- explained to some extent by their structural diversity. Figure 1 shows the general formula of iridoids. The authors [16] have established regiocontrol of the effect of the 1,6-anhydro bridge on the Dieckmann condensation of dicarboxylic acid diester 16, obtained in four steps from 13, the Diels–Alder adduct
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
- skin of human subjects were detected. However, evidence of ocular irritation at very low levels was obtained. Furthermore, it has been determined that 100–69% of methyl laurate is readily biodegraded aerobically following a 30-day period. The utilization of certain fatty acid methyl esters, including
- characteristics, arising from the ester group and the non-polar hydrocarbon chain, respectively. The nitrone contains a polar functional group (N–O) and two aromatic rings, which serve to generate both polar and dispersion forces. Consequently, these findings indicate that fatty acid methyl esters may possess
- demonstrated in Supporting Information File 1, Table S1, entries 14–16, the polarizability of fatty acid derivatives is greater than that of other solvents, resulting in their enhanced dispersing power. Consequently, the attraction to dissolved molecules is also stronger. Gu and Jérôme proposed a set of 12
An Fe(II)-catalyzed synthesis of spiro[indoline-3,2'-pyrrolidine] derivatives
Beilstein J. Org. Chem. 2025, 21, 2383–2388, doi:10.3762/bjoc.21.183
- , a highly diastereoselective method for the synthesis of dihydrospiro[indoline-3,2'-pyrrole]-2-ones has been developed (Scheme 1, path a) [7]. This transformation proceeds via a Lewis acid-mediated conjugate addition of vinyl azides to electron-deficient alkenes, followed by denitrogenative
- resulted in extensive decomposition and tarring, a common issue with α-unsubstituted pyrroles under acidic conditions. These results indicate that substrates featuring strongly electron-withdrawing groups or acid-sensitive motifs are not compatible with the developed protocol. Next, we synthesized the
Synthetic study toward vibralactone
Beilstein J. Org. Chem. 2025, 21, 2376–2382, doi:10.3762/bjoc.21.182
- this key intermediate in hand, β-hydroxy acid 29 was synthesized through deprotection, IBX oxidation, and Pinnick–Lindgren–Kraus oxidation and the β-lactone 13 was subsequently obtained through activation of the carboxylic acid. Although we successfully constructed the molecular scaffold of
Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications
Beilstein J. Org. Chem. 2025, 21, 2345–2366, doi:10.3762/bjoc.21.179
- base results in the deprotonation of the ammonium site and shuttling of the macrocycle to the urea site. Whereas, upon addition of acid, the macrocycle returns to the protonated BAA site. Notably, the rotaxane exhibited high fluorescence intensity due to aggregation in acetonitrile with high water
- along the axle in response to pH changes, moving farther from the spiropyran upon the addition of acid. In the spiropyran form, no FRET occurs between the tetraphenylethylene fluorophore on the macrocycle (donor) and the spiropyran unit, regardless of their relative positions. However, upon
- , temperature, and acid–base stimuli. Additionally, this spiropyran-based rotaxane showed pronounced photochromic and fluorescent behavior in both powder and solid film under alternating UV/sunlight and visible light/heating conditions, highlighting its suitability for dynamic optical systems and anti
Comparative analysis of complanadine A total syntheses
Beilstein J. Org. Chem. 2025, 21, 2334–2344, doi:10.3762/bjoc.21.178
- -oxidized analog and complanadines D and E are partially reduced analogs. In addition, natural analogs such as lycoplatyrine A (6), isolated as a mixture of diastereomers, were discovered as derivatives of lycodine and an amino acid [11]. Biosynthetically, lysine was proposed to be the starting point of
Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis
Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177
- -chloroperoxybenzoic acid) induced epoxidation, which was then followed by a Meinwald rearrangement to accomplish aldehyde 7. From 7, a sequence involving silyl enol ether formation, Simmons−Smith cyclopropanation, and acid-mediated regioselective ring-opening installed the C8 quaternary methyl group in 10. Subsequent
- , Yang's and Zhang's groups employed a quinone-based, acid-promoted Norrish–Yang cyclization to achieve the stereoselective construction of multiple avarane-type meroterpenoids [27], including dysiherbol A (33) [28], dysifragilone A (34) [29], dysideanone B (35) [30], dysideanone E (36) [28], and the core
- -benzoquinone – advanced 41 to neoavarone (44). After screening various Lewis acids (including AlCl3, Mg(OTf)2, Yb(OTf)3, etc.), it was finally found that treatment of 44 with irradiation at 422 nm in the presence of the optimal Lewis acid LaCl3 furnished the natural products dysiherbol A (33) and dysideanone E
Insoluble methylene-bridged glycoluril dimers as sequestrants for dyes
Beilstein J. Org. Chem. 2025, 21, 2302–2314, doi:10.3762/bjoc.21.176
- -surfaces and which are activated for electrophilic aromatic substitution reactions. For the synthesis of W1, we initially prepared tetramethoxybiphenyl 1 (Scheme 1) according to the literature procedure involving the Suzuki coupling between 3,4-dimethoxybromobenzene and 3,4-dimethoxyphenylboronic acid [44
- reaction of methylene-bridged glycoluril dimer G2BCE with aromatic walls W1–W4 conducted in trifluoroacetic acid (TFA) as both solvent and acid catalyst. The new hosts G2W1–G2W4 were obtained in 28, 33, 59, and 62% yield, respectively, after washing and recrystallization processes. Hosts G2W1–G2W4 are
- and were used without further purification. H2 was synthesized according to a previously published procedure [39]. NMR spectra were measured on commercial spectrophotometers at 400 MHz for 1H and 100 MHz for 13C in trifluoroacetic acid with a capillary tube containing deuterated water (D2O) for
Halogenated butyrolactones from the biomass-derived synthon levoglucosenone
Beilstein J. Org. Chem. 2025, 21, 2297–2301, doi:10.3762/bjoc.21.175
- . Short procedures for their synthesis have been developed starting with levoglucosenone, which can be obtained in a single step from the pyrolysis of acid-treated cellulose. The processes use inexpensive reagents for the stereoselective C3 functionalization of the bicyclic ring system, with a subsequent
- [14][15]. In recent years, the chiral biomass derivatives levoglucosenone (LGO, 5) and its reduced form Cyrene® (6) have gained increased attention as platforms for drug discovery [16][17][18][19]. The bicyclic ketone 5 is the major product from the pyrolysis of acid-treated cellulose [20], while its
- monochlorination and bromination of ketone 6 via enamine 9a [31], and it was envisaged that 9a would be a suitable substrate to achieve the double halogenation using an excess of electrophilic halogen. When enamine 9a was treated with 1.0 mol equivalent of trichloroisocyanouric acid (TCCA), a reagent which can
Enantioselective radical chemistry: a bright future ahead
Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174
- describes several important catalytic asymmetric strategies applied to enantioselective radical reactions, including chiral Lewis acid catalysis, organocatalysis, photoredox catalysis, chiral transition-metal catalysis and photoenzymatic catalysis. The application of electrochemistry to asymmetric radical
- transformations is also discussed. Keywords: chiral Lewis acid; electrochemistry; enantioselective radical reaction; organocatalysis; photoenzymatic catalysis; photoredox; Introduction Asymmetric catalysis plays an integral role in the enantioselective synthesis of organic compounds. A wide variety of
- the 1990s. Since then, meticulous research by several research groups has led to significant advances in this area [4][5][6][7][8]. This perspective focuses on several important contributions to the science of asymmetric radical reactions. Pioneering work on chiral Lewis acid catalysis and iminium
Pathway economy in cyclization of 1,n-enynes
Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173
- pathway-controlled approach using tryptamine ynamides bearing Michael acceptor moieties as substrates (Scheme 27) [38][39]. Under strong Brønsted acid catalysis, protonation of the carbonyl group was achieved, which facilitated a Michael addition between the electron-rich indole C3-position and the
- 133 (Scheme 27, path b). Through precise acid catalyst selection, the reaction pathways were strategically modulated to afford efficient construction of both 1H-pyrrolo[2,3-d]carbazole derivatives and spiro[indoline-3,3'-pyrrolidin]-2-one derivatives. In 2019, the Ye group reported a copper-catalyzed
- intramolecular cyclization of 1,7-enynes. Brønsted acid-catalyzed cycloisomerizations of tryptamine ynamides. Catalyst-controlled cyclization of indolyl homopropargyl amides. Angle strain-dominated 6-endo-trig cyclization of propargyl vinyl ethers. Angle strain-controlled cycloisomerization of alkyn-tethered
Research towards selective inhibition of the CLK3 kinase
Beilstein J. Org. Chem. 2025, 21, 2250–2259, doi:10.3762/bjoc.21.172
- [22]. But because our goal is to enhance activity for CLK3, we cannot take advantage of this amino acid variation, and we had to investigate for other differences between CLKs. Here, we report our strategy and first efforts towards this end, starting from compound DB18 which is highly potent and
- , examination of the structure of CLK3 shows that this key lysine 241 is very close to the entry of the ATP binding site (Figure 1B). Lysine 241 could be considered as an opportunity to design new molecules with an improved affinity to CLK3, by adding specific interactions with this amino acid bearing a primary
- amine in terminal position. Based on this, our strategy was to design new inhibitors with introduction, in their terminal part, of an acid group which could perform an extra hydrogen bond or a salt bridge with lysine 241 and therefore could be specific to CLK3. Towards this goal we started from our
A chiral LC–MS strategy for stereochemical assignment of natural products sharing a 3-methylpent-4-en-2-ol moiety in their terminal structures
Beilstein J. Org. Chem. 2025, 21, 2243–2249, doi:10.3762/bjoc.21.171
- derivatization. Several derivatization methods using chiral anisotropic reagents, including α-methoxy-α-trifluoromethylphenylacetic acid (MTPA), phenylglycine methyl ester (PGME), and Marfey’s reagents, are widely used [8][9][10], although their applicability is restricted by the presence of specific functional
- Discussion Our degradation strategy of natural products bearing an MPO moiety includes (1) acylation of hydroxy group, (2) oxidative cleavage of olefin to generate 3-acyloxy-2-methylbutanoic acid, and (3) its methyl esterification (Scheme 1A). We initially investigated derivatization strategies to enable LC
- . Alternatively, PNB ester (2S,3R)-9, the C3-epimer of 8, was synthesized from (2S,3S)-13 via a Mitsunobu reaction using p-nitrobenzoic acid (PNBOH) and DEAD in 39% yield for two steps [28]. The stereoisomers (2R,3R)-10, and (2R,3S)-11 were prepared in the same manner starting from commercially available (3R)-14
Thiadiazino-indole, thiadiazino-carbazole and benzothiadiazino-carbazole dioxides: synthesis, physicochemical and early ADME characterization of representatives of new tri-, tetra- and pentacyclic ring systems and their intermediates
Beilstein J. Org. Chem. 2025, 21, 2220–2233, doi:10.3762/bjoc.21.169
- were previously used for the synthesis of 7-nitroindole derivatives: heating in polyphosphoric acid (PPA) at 80 °C [24][25]. However, our attempt was not successful. Experiments with zinc chloride, the most commonly used Lewis acid catalyst in Fischer indole syntheses, also failed under various
- conditions. Finally, we were able to achieve the Fischer cyclization of compounds 7a–j by using p-toluenesulfonic acid monohydrate as catalyst in boiling toluene (method A, step 2) [26][27]. On the other hand, the one-pot synthesis of target compounds 3a–j starting from hydrazino derivatives 5a,b was
- 1) afforded hydrazones (E)-9a,b. According to LC–MS, only the (E) isomers were present in the reaction mixtures and in the crude products. Hydrazones (E)-9a,b were then cyclized by refluxing in toluene in the presence of p-toluenesulfonic acid monohydrate (method A, step 2). It is noteworthy that
A m-quaterphenyl probe for absolute configurational assignments of primary and secondary amines
Beilstein J. Org. Chem. 2025, 21, 2211–2219, doi:10.3762/bjoc.21.168
- Shibazono, Narashino, Chiba 275-0023, Japan Research Center for Materials with Integrated Properties, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan 10.3762/bjoc.21.168 Abstract We report a method for determining the absolute configurations of chiral amino alcohols, amino acid esters, and
- amines. In this work, we report that the method was applied to chiral amino alcohols and amino acid esters. We also applied the method to chiral secondary amines, for which it is generally difficult to determine the absolute configuration due to the conformational complexity of their derivatives [33]. By
- comparing the observed and calculated sign of the CD Cotton effect, their absolute configurations were determined. Results and Discussion The probe 1 was prepared as described previously [41]. Probe 1–primary amine conjugates 2a–e were prepared by the reaction of 1 with chiral amino alcohols and amino acid
Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings
Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166
- following: a mixture 3-functionalized indole 19 (0.08 mmol), 2-alkynylaniline 20 (0.12 mmol), (R)-Rh1 (5 mol %), n-Bu4NOAc (0.08 mmol), 1-adamantane carboxylic acid (1-AdCO2H, 0.08 mmol) and MeOH/CHCl3 (1:1, 2 mL), under electrolysis (graphite felt (GF) anode and graphite (C) cathode, 2 mA, 5.6 F/mol) at rt
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