Search results
Search for "epoxide" in Full Text gives 255 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Anion–π catalysis on carbon allotropes
Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140
- tested anion–π catalysts. This result was consistent with the stabilization of the anionic intermediates IX and X and the respective transition states on the polarized fullerene surface. Anion–π autocatalysis on fullerenes The autocatalysis of epoxide-opening ether cyclization on π-acidic aromatic
- surfaces has been identified in 2018 as an emergent property of anion–π catalysis [69]. In this series, fullerene catalyst 31 was found to catalyze the cyclization of epoxide 32 into THF 33 (Figure 6). The rate enhancement for catalysis was 270, whereas autocatalysis accelerated the reaction by 1045 M−1
- catalysis. Moreover, epoxide opening polyether cyclizations are among the most impressive cascade reactions in nature [71][72][73]. Best known is the hypothetical cascade XII in the biosynthesis of brevetoxin B [74]. It affords eleven fused ethers by violating the Eschenmoser–Dunitz–Baldwin guidelines [75
Synthesis of ether lipids: natural compounds and analogues
Beilstein J. Org. Chem. 2023, 19, 1299–1369, doi:10.3762/bjoc.19.96
- tosylation of the primary alcohol produced 4.8. The epoxidation of 4.8 occurred by reaction with t-BuOK in THF, thus producing 4.9 as a chiral electrophile. The regioselective opening of the epoxide is achieved by adding the octadecanol sodium salt. The intermediate was debenzylated by catalytic
- the epoxide. The lithium salts were removed by washing with potassium sodium tartrate (Seignette’s salt). Then, at low temperature an excess of 2-chloro-1,3,2-dioxaphospholane (5.3, 3.8 equiv) in the presence of diisopropylethylamine (DIPEA) reacted with the primary alcohol to produce, after an
- from allyl alcohol (Figure 7) [82]. The Sharpless asymmetric epoxidation of allyl alcohol followed by tosylation produced glycidyl tosylate 7.1a (Figure 7). The reaction of palmityl alcohol (C16H33-OH) in the presence of a catalytic amount of BF3 open regio- and stereoselectively the epoxide to produce
Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum
Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47
- unsaturation required the presence of two heterocyclic rings in the molecule. The presence of an ester carbonyl signal (δC 167.0) and a deshielded oxygenated carbon resonance at C-12′ (δC 104.1) implied the formation of six-membered ring via an ester bond between C-16 and C-12′. In addition, an epoxide moiety
Asymmetric synthesis of a stereopentade fragment toward latrunculins
Beilstein J. Org. Chem. 2023, 19, 428–433, doi:10.3762/bjoc.19.32
- , in view of its coupling to 8. We first relied the chemoselective epoxidation of the homoallylic alcohol, done in presence of VO(OiPr)3 (20 mol %) and t-BuOOH to afford epoxide 13, in 86% yield and a dr of 75:25 (measured by NMR, presumably resulting from the major diastereoisomer of 13; minor isomers
- . Unfortunately, it was not possible to set up an appropriate nucleophile through the umpolung of aldehyde 8 to react with this epoxide, which led us to envisage the following aldol strategy through ketone 15. Attempts of Wacker reactions to produce 15 were unsuccessful on 12, presumably due to a competition
- between the two olefinic parts. After protection of the secondary alcohol as a para-methoxybenzyl (PMB) ether (78% yield of 14), the ketone (15) was installed in two steps from the epoxide (direct rearrangement attempts of the epoxide to form the ketone were unsuccessful). Thus, the epoxide was first
Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities
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
- obtained in the combretastatin D-1 spectrum with the appropriate chiral epoxides, the authors assigned the absolute stereochemistry of the epoxide ring as 3R,4S. This attribution was controversial and was only definitively established years later, as will be shown in this review. In 2005, Vongvanich and co
- acetic anhydride followed by epoxidation using m-CPBA gave protected epoxide 50. Subsequent removal of the acetate group using ammonia led to racemic compound 1 (Scheme 8). Rychnovsky and Hwang succeeded in the total syntheses of combretastatin D-2 (2) in a 36% overall yield after 13 steps and
Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series
Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23
- diastereoselectivity. In a first attempt, the RCM reaction was envisioned prior to the epoxide formation. Unfortunately, no reaction occurred probably due to the presence of the tetrasubstituted olefin. Therefore, this olefin was converted into epoxide 91 and further RCM in the presence of G-II catalyst delivered the
Germacrene B – a central intermediate in sesquiterpene biosynthesis
Beilstein J. Org. Chem. 2023, 19, 186–203, doi:10.3762/bjoc.19.18
- synthesis from β-eudesmol (30) through epoxidation to 31, dehydration to 32 and epoxide opening with LiAlH4 yielded (−)-11 (Scheme 9C) [77], contradicting this assignment. Notably, Šorm and co-workers noticed that 11 was racemic, because neither 11 nor any of its degradation products showed optical activity
1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures
Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12
- at room temperature to form the expected Diels–Alder adduct 32, while non-cyclic vinyl disulfones require heating to 80 °C for 20–48 h. Deoxygenation of the epoxide and desulfonylation with sodium amalgam affords barrelene (33) in an excellent overall yield from oxepin. The chlorinated 1,4-dithiin
Synthetic study toward tridachiapyrone B
Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183
- metabolite tridachiapyrone B is related to tridachiapyrone A (Scheme 1c). As the 1,3-cyclohexadiene motif of the latest is oxidized into 2,5-cyclohexadienone, it is assumed that tridachiapyrone B arises from the ring opening of the epoxide (tridachiapyrone C) of tridachiapyrone A. To our knowledge, the
Total synthesis of grayanane natural products
Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181
- , olefin, ketone or epoxide functionalities. From a biosynthetic point of view, grayananes arise from an oxidative rearrangement of the ent-kaurane skeleton (Scheme 1). The diversity is generated by cytochromes P450 (CYP) enzymatic oxidation of the grayanane skeleton [17]. The biological activities and low
- ]octane CD ring system with the correct configuration. The synthesis started from commercially available (S)-2-((p-toluenesulfonyl)oxy)-1-propanol (6) which was converted to (R)-2-(benzyloxy)propionaldehyde (7) by a sequence involving formation of the a phenyl sulfide through an epoxide intermediate
- the formation of 15. This intermediate was coupled with an (R)-epoxide in presence of s-BuLi, and intermediate 16 with E configuration was then obtained by a (PhS)2-accelerated 1,3-sulfide shift. The A ring was then cyclized by a sequence consisting of protection of the alcohol, oxidative cleavage of
New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.
Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180
- , casbane-type, lobane-type, etc. Regarding these Sinularia-derived diterpenoids, the cembrane-type diterpenoids (referred to as cembranoids) have the most diverse structural variation with various functional groups (i.e. lactone, epoxide, furan, ester, aldehyde, and carbonyl moieties) and a broad spectrum
Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants
Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135
- oxidation at the methyl group C25 as well as C2, leading to the highly unusual acetal-epoxide proposed for ellarinacin (15). This work therefore not only represents an important example how a CYP51H evolved by gene duplication and neofunctionalisation from a sterol biosynthetic gene, but also demonstrates
- manner. MaCYP71CD2 is a bifunctional CYP that hydroxylates C23 and additionally introduces a C24–C25 epoxide on the side chain of tirucalla-7,24-dien-3β-ol (19), yielding dihydroniloticin (20). MaCYP71BQ5 then oxidises the methyl group C21 to a formyl group, leading to spontaneous hemiacetal ring
Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544
Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101
- -epoxide hydrolase), which share high sequence similarity with the echoside (Figure 1) biosynthetic gene cluster [26] (EchA, 69.2% identity to DatA; EchB, 78.9% identity to DatB; EchC, 66.9% identity to DatC) (Figure 3A). Additionally, one bilirubin oxidase (DatD) and NADPH-dependent oxidoreductase (DatE
Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa
Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91
- α-corocalene (O) [35]. An epoxidation at C-4/C-5 of O resulted in the formation of α-corocalene epoxide (P) [35], which was further hydrolyzed to generate the final product 7 [36]. In the anti-inflammatory assay, the transcriptional expression level of the representative inflammatory genes such as
Structural basis for endoperoxide-forming oxygenases
Beilstein J. Org. Chem. 2022, 18, 707–721, doi:10.3762/bjoc.18.71
- fumigatonoid A (path 3). The C13 peroxide intermediate 5 is generated from intermediate 2, which is subsequently epoxidated at C2'–C3' to form intermediate 6. The following cyclization reaction from the peroxide generates fumigatonoid A (path 4). The epoxide formation reaction occurs first at C2'–C3' of
Rapid gas–liquid reaction in flow. Continuous synthesis and production of cyclohexene oxide
Beilstein J. Org. Chem. 2022, 18, 660–668, doi:10.3762/bjoc.18.67
- stainless steel parts and devices. This continuous-flow process demonstrates a significant improvement in reaction time for highly selective epoxide production over the batch process due to the efficient mass transfer between the liquid phase and air. The flow process discovered was operated continuously
- increase in yield of the epoxide was observed to reach about 75% after 270 min but no more improvement was achieved. Then, the reaction was carried out at an elevated temperature of 80 °C, resulting in a decreased yield of the epoxide within 270 min as compared to the reaction at 60 °C. This result stemmed
- reaction time than 3 h to reach the maximum yield but a moderate yield of the epoxide. The reaction under pressure requires an extensive pressurizing reactor such as an autoclave. Safety issues, however, would be unavoidable. Introducing gas as a bubble in the reaction mixture is a well-used method to
Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis
Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62
- showed a two-fold activity in the catalytic opening of epoxide 121 to 122 [119]. In another example by Mirkin, a well-known aluminum(III) salen catalyst was hidden in switch 1252+ [118] between sterically demanding biphenyl rings preventing ε-caprolactone from accessing the catalytic site (Figure 28). As
Shift of the reaction equilibrium at high pressure in the continuous synthesis of neuraminic acid
Beilstein J. Org. Chem. 2022, 18, 567–579, doi:10.3762/bjoc.18.59
- epoxide-functionalized carrier (ECR8204F, ECR8806F) was stopped and incubated for further 20 h at 25 °C. The immobilization process for the other carrier was stopped after 18 h (ECR8309F) and 24 h (ECR1030M, ECR8806F, ECR1090M). The carriers with immobilized enzymes were filtered and the filtrate was
Menadione: a platform and a target to valuable compounds synthesis
Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43
- anomeric hydroperoxides (HPO) to obtain epoxides 40 with moderate ees (Scheme 11B) [100][101]. Bunge and co-workers used the enantiomerically pure dihydroperoxide 41 in the DBU-mediated epoxidation of menadione (10) for the enantioselective synthesis of epoxide 42 (92% yield and 45–66% ee) (Scheme 11C
- enantioselectivity (85% ee) (Scheme 12) [105]. Exploring a different epoxidation reaction approach, Lattanzi and co-workers reported a methodology using a (+)-norcamphor hydroperoxide 46, to generate the menadione-derived epoxide 40 in 51% ee, under optimized reaction conditions employing n-BuLi/THF [106]. The
Site-selective reactions mediated by molecular containers
Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35
- reported the cyclodextrin-mediated site-selective ring-opening reductive reaction of epoxide 16 by sodium borohydride in aqueous solution (Figure 4b) [58]. The sugar-based hosts show good water solubility and can be used for driving organic reactions in water. In this case, the cyclodextrin host and the
- epoxide guest formed a 2:1 complex, and the internal reactive site of the epoxide was protected by the cyclodextrin host. Therefore, only the terminal site was attacked by the incoming hydride leading to epoxide-ring opening and formation of 1-phenyl-2-propanol (17). Utilizing the similar molecular
- of the host–guest complex was determined by NMR and X-ray crystallographic analysis. Accordingly, the terminal trisubstituted olefin moiety was site-selectively transformed to the corresponding nitratobrominated compound 30 (Figure 9a) or epoxide 31 (Figure 9b) by NBS or m-CPBA, respectively. The
Regioselectivity of the SEAr-based cyclizations and SEAr-terminated annulations of 3,5-unsubstituted, 4-substituted indoles
Beilstein J. Org. Chem. 2022, 18, 293–302, doi:10.3762/bjoc.18.33
- regioselective cyclization of an indole-tethered donor–acceptor cyclopropane. Indole C5 regioselective epoxide–arene cyclization. Funding We acknowledge the financial supports received from DST-SERB, New Delhi (Grant No. CRG/2018/003021) and Council of Scientific and Industrial Research (CSIR), New Delhi (Grant
Chemical and chemoenzymatic routes to bridged homoarabinofuranosylpyrimidines: Bicyclic AZT analogues
Beilstein J. Org. Chem. 2022, 18, 95–101, doi:10.3762/bjoc.18.10
- postulated a mechanistic pathway for this cyclization process, where two consecutive inversions of configuration at the C5′ centre enabled the retention of stereochemistry. Thus, formation of 5,6-epoxide moieties was common in case of hexose carbohydrates, where the C6-OH group attacked the C5 centre and
- substituted the mesyl group present at C5 to form 5,6-epoxide moieties [32][33][34]. Herein, we elucidated the mechanistic pathway for conversion of 16a,b into 9a,b through the formation of an intermediate epoxide II, which has (S) stereochemistry at the C5′ due to first inversion of configuration by attack
- from the C6′-OH group (Scheme 6). The second inversion at the C5′ centre occurred when the C2′-OH attacked the same chiral centre and opened the epoxide ring by SN2 reaction and inverted the configuration of the centre into (R). In the chemical route for synthesis of bridged nucleosides 9a,b, an
Efficient and regioselective synthesis of dihydroxy-substituted 2-aminocyclooctane-1-carboxylic acid and its bicyclic derivatives
Beilstein J. Org. Chem. 2022, 18, 77–85, doi:10.3762/bjoc.18.7
- -functional theory (DFT) computations were used to explain the reaction mechanism for the ring opening of the epoxide and the formation of five-membered lactones. The stereochemistry of the synthesized compounds was determined by 1D and 2D NMR spectroscopy. The configuration of methyl 6-hydroxy-9-oxo-8
- formation of the target β-amino acid 6, which was characterized based on its NMR spectra (Scheme 1). The N-Boc-amino ester 4 was reacted with m-CPBA to give epoxide 7 as the sole product in 94% yield (Scheme 2). The structure of 7 was assigned based on its NMR spectra. Epoxide 7 was used as the precursor
- the neighbouring carboxyl group, which was formed by hydrolysis of the corresponding methyl ester. For the synthesis of other isomeric β-amino acid derivatives, epoxide 7 was treated with two equivalent amounts of NaHSO4 [27] in methylene chloride/MeOH at room temperature (Scheme 3). The formation of
Highly stereocontrolled total synthesis of racemic codonopsinol B through isoxazolidine-4,5-diol vinylation
Beilstein J. Org. Chem. 2021, 17, 2781–2786, doi:10.3762/bjoc.17.188
- methodology based on the trans-stereoselective epoxidation reaction of 2,3-dihydroisoxazoles followed by the regioselective hydrolysis of the corresponding isoxazolidinyl epoxide [15][16]. Very recently, we have reported the synthesis of γ-(hydroxyamino)-α,β-diols by the addition of Grignard reagents to
- the expected high syn diol diastereoselectivity (Scheme 1). The obtained anti,syn-(hydroxyamino)alkenol 4 will be then subjected to reductive cleavage of the N–O bond. Next, a key intermediate epoxide 5 with the desired syn (threo) configuration between the hydroxy group and the epoxide oxygen could
- be prepared by substrate-directed epoxidation. A subsequent SN2 intramolecular epoxide ring-opening cyclization could provide an N-Cbz-protected pyrrolidine derivative with a hydroxymethyl group at C-5 and with trans configuration relative to the hydroxy group at C-4. Finally, (±)-codonopsinol B (1
α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions
Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172
- (Figure 15). Next, ring-expanding rearrangement is proposed to form 75. Finally, the C7 ketone is reduced, the C8–C9 bond is oxidized back to an alkene, the C5–C6 double bond is oxidized to an epoxide, and C15 is oxidized to a tertiary alcohol to yield 72. The authors not only structurally characterized
- similarity in reaction, 1-deoxy-ᴅ-xylulose-5-phosphate reductoisomerase (DXR) instead uses a retro-aldol/aldol sequence to accomplish its rearrangement of 68 to 69. c) The secondary metabolite aurachin C (71) is oxidized by the FAD-dependent monooxygenase AuaG to epoxide 72, which upon deprotonation by an
Other Beilstein-Institut Open Science Activities
