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Search for "chromatographic separation" in Full Text gives 100 result(s) in Beilstein Journal of Organic Chemistry.
Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry
Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66
- scalable, amenable to chromatographic separation and reproducible difunctionalization methods. Moreover, the direct NMR spectroscopic analysis would provide structure elucidation without any reference material, time-consuming chemical conversions or enzymatic degradation. Hetero-difunctionalized CDs are
Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines
Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41
- excellent yields of 2,6-diazidopurines 2a–c in the range from 66 to 93%. In several cases chromatographic separation of the N(9)/(7) isomers was easier at the stage of diazido products 2a and 2a’. Diazido products 2 are light and temperature sensitive [48], but can be stored without degradation in
Synthesis of nonracemic hydroxyglutamic acids
Beilstein J. Org. Chem. 2019, 15, 236–255, doi:10.3762/bjoc.15.22
- )-5 which after O-benzylation provided an inseparable 1:3 mixture of compounds 8a and 8b. A six-carbon chain was shortened by a diol formation–diol cleavage sequence followed by aldehyde oxidation and esterification to give 9a and 9b after chromatographic separation. They were transformed into (2S,3R
- (Scheme 11) [60]. Sharpless epoxidation of the allylic alcohol 48 gave a 46:11:33 mixture of (S)-48, (3R,4S)-49 and (2R,3R)-50. While (S)-48 is a product of kinetic resolution, the formation of (2R,3R)-50 results from the intramolecular opening of the oxirane ring in (3R,4S)-49. After chromatographic
- separation the hydroxy groups in (2R,3R)-50 were protected as silyl ethers to allow oxidation at C5 to produce pyrrolidine-2-one (4R,5R)-47 (Scheme 12) which was later transformed into (2S,3R)-34 as already shown (Scheme 11) [61]. From L-malic acid (S)-Acetoxypyrrolidin-2,5-dione (51), readily available from
A tutorial review of stereoretentive olefin metathesis based on ruthenium dithiolate catalysts
Beilstein J. Org. Chem. 2018, 14, 2999–3010, doi:10.3762/bjoc.14.279
- reactions a 1:3 ratio of A/B was applied. Practical limitations are that A and B have to be of significantly different polarity for easy column chromatographic separation and that sterically hindered olefins are not tolerated. For some alkenes, e.g., styrenes, the homodimerization is too fast leading to
Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum
Beilstein J. Org. Chem. 2018, 14, 2974–2990, doi:10.3762/bjoc.14.277
- of Scheme 2. Note that because of an isotope effect the isotopomers of 24 can be separated by gas chromatography depending on their deuterium content [34][35], which makes the usage of (methyl-2H3)methionine superior to the usage of 13C-labelled methionine that would not have led to chromatographic
- separation of the isotopomers. In conjunction with the low incorporation rates obtained here, the results would have been difficult to interpret. Another trace compound emitted by H. griseobrunneum showed a molecular ion at m/z = 136 and coeluted with exactly the same retention time as a second compound with
Investigation of the electrophilic reactivity of the biologically active marine sesquiterpenoid onchidal and model compounds
Beilstein J. Org. Chem. 2018, 14, 2229–2235, doi:10.3762/bjoc.14.197
- dialdehyde 11 with dialdehyde 12 (1:1). Attempts at chromatographic separation of these two isomers resulted in degradation of 12. Final conversion of 11 to enol acetate 13 was achieved by overnight reaction with pyridine and acetic anhydride. Purification by silica gel column chromatography afforded the
Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3+ + 2]-cycloaddition/rearrangement reactions
Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155
- unstable and tended to degrade when it was subjected to chromatographic separation. Based on this, we planned to use the product mixture resulting from the oxidation of hydrazone 11 directly for the following reaction with nitriles 9 in the presence of AlCl3. We were pleased to observe that the reaction
Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)
Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9
- synthesis (Scheme 5), the pure racemates of 11a–d and the pure enantiomers of 11a, 11b and 11d were obtained by chromatographic separation from the synthetic mixture of all eight stereoisomers. The peak labelled with asterisk represents the second main natural product in the headspace extracts from D
Aminomethylation/hydrogenolysis as an alternative to direct methylation of metalated isoquinolines – a novel total synthesis of the alkaloid 7-hydroxy-6-methoxy-1-methylisoquinoline
Beilstein J. Org. Chem. 2018, 14, 130–134, doi:10.3762/bjoc.14.8
- material 3. Due to the very similar polarities of 3 and 4, chromatographic separation was very tedious, and only 34% of methyl compound 4 was isolated, accompanied by about 30% of starting material 3 and mixed fractions. Debenzylation of 4 by catalytic hydrogenation in methanol solution under palladium
- naphthalene-derived natural product plumbagin. In fact, trapping 1-metalated isoquinoline 3 with Eschenmoser’s salt gave the aminomethyl derivative 5 in 37% yield. Chromatographic separation from starting material 3 (recovered yield: 32%) was unproblematic. Surprising results were obtained in our
Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin
Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248
- positions 2-O-, 3-O-, and 6-O- were developed. The alkylation reagent 2-(3-chloroprop-1-enyl)naphthalene, used for the reactions, can be easily prepared in large quantities without the need for chromatographic separation. The method originally expected to be used for the preparation of the regioisomers
Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis
Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228
- afforded the syn,anti-epoxy alcohol 28b with good stereoselectivity, albeit in poor yield. One reason for the low yield of 28b was the difficulty in its chromatographic separation from the byproducts of the epoxidation reaction. Nevertheless, a sufficient quantity of 28b was obtained to proceed some way
A novel application of 2-silylated 1,3-dithiolanes for the synthesis of aryl/hetaryl-substituted ethenes and dibenzofulvenes
Beilstein J. Org. Chem. 2017, 13, 1900–1906, doi:10.3762/bjoc.13.185
- smoothly converted into the corresponding tetraarylethenes 9d–f (Table 1). However, in these cases, mixtures of (Z)- and (E)-isomers were formed and isolated in 65–75% yield. In all cases, the ratio of isomers was calculated to ca. 3:2 (1H NMR); however, the attempted chromatographic separation was
A speedy route to sterically encumbered, benzene-fused derivatives of privileged, naturally occurring hexahydropyrrolo[1,2-b]isoquinoline
Beilstein J. Org. Chem. 2017, 13, 1413–1424, doi:10.3762/bjoc.13.138
- product could be recovered from the filtrate in the form of respective methyl esters after O-methylation and chromatographic separation (see Experimental section): syn-10a' (7%), anti-10a' (12%), syn-10b' (13%). In those cases when the carboxylic acid precipitate contained a significant proportion of the
- 9), isolation of pure diastereomeric CCR adducts was achieved by total esterification of the carboxylic acid product mixture and chromatographic separation of the respective methyl esters (the 0.8:1 anti/syn-10e mixture stereoconverged to anti-10e' on esterification, vide infra). The trans
Synthesis of oligonucleotides on a soluble support
Beilstein J. Org. Chem. 2017, 13, 1368–1387, doi:10.3762/bjoc.13.134
- . Although chromatographic separation appears to be a tedious procedure compared to precipitation or extraction, it has been successfully applied to the synthesis of ODNs on a soluble support. The studies of Wörl and Köster on N1,N3,N5-tris(2-aminoethyl)benzene-1,3,5-tricarboxamide derivatized with 3´-O
- oxidizing agent was removed by coevaporation with THF and MeOH, and the residue was dissolved into an 80:19:1 mixture of DCM, MeNO2 and MeOH. Finally, the 5´-terminal DMTr groups were removed by adding 2% TFA. After neutralization with Et3N, the chromatographic separation was repeated. Upon assembly of a
- − 1 fragment was formed in a considerable amount. Assembly from dimeric phosphoramidites was additionally attempted, but the chromatographic separation was not efficient enough to remove the excess of the dimeric building block. Much later chromatographic separation was exploited for the assembly of
Synthesis of alkynyl-substituted camphor derivatives and their use in the preparation of paclitaxel-related compounds
Beilstein J. Org. Chem. 2017, 13, 1230–1238, doi:10.3762/bjoc.13.122
- =N carbon is more electrophilic. Steric and electronic properties thus counteract and the overall selectivity of the reaction depends on a balance between both factors. Whilst chromatographic separation of the mixture of the monoadducts 12 + 13 from the starting material 3 and the bis-adduct 4 is
Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)
Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50
- indicated the presence of a wide range of secondary metabolites. These VLC fractions were thus subsequently submitted for further chromatographic separation. VLC fraction 7 (690 mg) was further separated by normal phase VLC using silica gel (60Å, 70–230 mesh, 63–200 µm) and dichloromethane (DCM):acetone
Supramolecular frameworks based on [60]fullerene hexakisadducts
Beilstein J. Org. Chem. 2017, 13, 1–9, doi:10.3762/bjoc.13.1
- remove the solvent and traces of unreacted C60. After further column chromatographic separation (SiO2; toluene/ethyl acetate 10:1), pure hexakisadduct 2 (600 mg, 197 µmol, 25%) was obtained as a yellow crystalline solid. mp >200 °C dec; 1H NMR (400 MHz, CDCl3, rt) δ 1.44 (s, 108H, C(CH3)3), 1.99 (m, 3J
O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside
Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282
- activated using TMSBr and different retention times of pyranosyl bromides and undesired furanosyl bromides on TLC were observed. However, preparative chromatographic separation failed probably due to an enhanced reactivity of the partially ‘armed’ ether protected halogen glycosides [38] and degradation was
New syntheses of (±)-tashiromine and (±)-epitashiromine via enaminone intermediates
Beilstein J. Org. Chem. 2016, 12, 2609–2613, doi:10.3762/bjoc.12.256
- found that the bicyclic vinylogous urea 9d (64%) required a more careful flash chromatographic separation [19]. Unfortunately, the bicyclic vinylogous amide 9a could not be separated adequately from the triphenylphosphine residues under standard chromatographic and recrystallisation conditions. In an
Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis
Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250
- nucleoside 7 in 28% yield after chromatographic separation from the corresponding 3’-regioisomer. Finally, the 5’-O-DMTr-2’-O-TIPS protected 3-deazaadenosine derivative 7 was converted into the phosphoramidite building block 8 with 2-cyanoethyl diisopropylchlorophosphoramidite in the presence of N
Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B
Beilstein J. Org. Chem. 2016, 12, 2523–2534, doi:10.3762/bjoc.12.247
- ) silica. Racemic naringenin was purchased from Sigma-Aldrich and used without further purification. Preparative HPLC Chemicals and reagents Acetonitrile used in the preparative chromatographic separation was gradient grade LiChrosolv purchased from Merck. The formic acid was reagent grade from Sigma
Development of a continuous process for α-thio-β-chloroacrylamide synthesis with enhanced control of a cascade transformation
Beilstein J. Org. Chem. 2016, 12, 2511–2522, doi:10.3762/bjoc.12.246
- efficient rapid heating poses practical difficulties for scale-up and, furthermore, chromatographic separation is required to remove product impurities. The nature of the aforementioned difficulties outlined are, however, largely specific to the scale-up of batch chemistry. A continuous processing approach
- % can be obtained under batch conditions, incomplete conversion to α-thioamide 2 necessitates a difficult, and often laborious, chromatographic separation, as starting material 1 and product 2 are poorly resolved. Indeed, high-purity batches of α-thioamide 2 are often not achieved by chromatography
Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products
Beilstein J. Org. Chem. 2016, 12, 2125–2135, doi:10.3762/bjoc.12.202
- than it has been predicted by calculations (see Table 1). It should be noted, that the yields of reaction products in Tables 3–5 are isolated yields after column chromatographic separation. The remaining materials are some oligomeric compounds. Using these conditions (TfOH, rt, 1 h), we carried out
A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis
Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176
- reactions guanidine 10 is not optimal for the preparation of Diels–Alder adducts. We therefore focussed our efforts on the Michael products: Anthrone 20 and maleimide 22 reacted with 0.1 equiv of 10 in THF at −15 °C for 64 h. Chromatographic separation then yielded 51% of 25 and 42% of Michael product 28
Practical synthetic strategies towards lipophilic 6-iodotetrahydroquinolines and -dihydroquinolines
Beilstein J. Org. Chem. 2016, 12, 1851–1862, doi:10.3762/bjoc.12.174
- complex followed by an elimination process that is favoured at higher temperature, as postulated in Scheme 9. Chromatographic separation of compounds 21 and 22 on silica resulted in co-elution; however, the two compounds could be separated on neutral alumina using a non-polar eluent. Selectivity for 22 on
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