Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• ion intermediate in a stereoselective manner for THP ring formation as shown in Scheme 3. The outcome of exclusive cis-stereoselectivity in the Prins cyclization might be attributed to the most favorable conformation adopted by 12 with equatorial orientation of the 2,6-substituents (R1 and R2). Alder

Menthyl esterification allows chiral resolution for the synthesis of artificial glutamate analogs

• Kenji Morokuma,
• Shuntaro Tsukamoto,
• Kyosuke Mori,
• Kei Miyako,
• Ryuichi Sakai,
• Raku Irie and
• Masato Oikawa

Beilstein J. Org. Chem. 2021, 17, 540–550, doi:10.3762/bjoc.17.48

• conversion of oxanorbornene (rac)-13 to heterotricycle (rac)-16 through the eight-membered-ring formation would be owing to the cis-relationships of the pentenyl and vinyl groups on the ring B of (rac)-15, which allows the proximal arrangement of the reacting sites in the RCM. The N-Boc derivatization of

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• that a specific geometry of the tethered alkene is required, as no 6-membered ring formation was observed. Interestingly, Cárdenas’ precursor 35 [30] led, after a cascade of reactions, to the formation of compound 36. Computational as well as experimental studies suggested that the ligand and

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• catalyst 2 with (NH4)2S2O8, which acted as a cost-efficient and environmentally friendly oxidant (Scheme 14) [139]. In the mechanism, the excited photocatalyst generates the benzoyloxy radical 98, and the cyclization of 98 is completed via 6-endo-trig ring formation to form the intermediate 99, which, upon

Combining the Ugi-azide multicomponent reaction and rhodium(III)-catalyzed annulation for the synthesis of tetrazole-isoquinolone/pyridone hybrids

• Gerardo M. Ojeda,
• Prabhat Ranjan,
• Pavel Fedoseev,
• Lisandra Amable,
• Upendra K. Sharma,
• Daniel G. Rivera and
• Erik V. Van der Eycken

Beilstein J. Org. Chem. 2019, 15, 2447–2457, doi:10.3762/bjoc.15.237

• activation of the N-benzamidomethyltetrazole core followed by isoquinolone-ring formation to furnish 4a. We endeavored two catalytic systems based on ruthenium and rhodium, which in our laboratory have proven success in this type of cyclization [32][48]. First, the alkynylation protocol was attempted using

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• functionalities are apart from each other. However, an individual intramolecular coupling reaction of 8 and 9 using CMPI as a coupling reagent, in the presence of Et3N in dichloromethane, afforded pseudodipeptide 1 and pseudotetrapeptide 2a, respectively, with oxazolone ring formation at the C-terminal of the

In water multicomponent synthesis of low-molecular-mass 4,7-dihydrotetrazolo[1,5-a]pyrimidines

• Irina G. Tkachenko,
• Sergey A. Komykhov,
• Vladimir I. Musatov,
• Svitlana V. Shishkina,
• Viktoriya V. Dyakonenko,
• Vladimir N. Shvets,
• Mikhail V. Diachkov,
• Valentyn A. Chebanov and
• Sergey M. Desenko

Beilstein J. Org. Chem. 2019, 15, 2390–2397, doi:10.3762/bjoc.15.231

• starting material and subsequent dihydropyrimidine ring formation. The first approach [6][7] represents a two-component cyclocondensation of 5-aminotetrazole (1) as binucleophilic component and bielectrophilic α,β-unsaturated carbonyl compounds 2 (Scheme 1, reaction 1). The second method [8][9][10][11][12

• several times [5][6]. A third approach (Scheme 1, reaction 3) is completely different and consists of the tetrazole ring formation through cyclization of dihydropyrimidinethiones with sodium azide [14]. Generally, all three approaches allow for the preparation of a broad range of compounds 3 with a wide

Inherent atomic mobility changes in carbocation intermediates during the sesterterpene cyclization cascade

• Hajime Sato,
• Takaaki Mitsuhashi,
• Mami Yamazaki,
• Ikuro Abe and
• Masanobu Uchiyama

Beilstein J. Org. Chem. 2019, 15, 1890–1897, doi:10.3762/bjoc.15.184

• 5/6/8/5 tetracyclic intermediate. This, in turn, is transformed to a 4/6-membered ring in quiannulatene biosynthesis, whereas 5/5 ring formation proceeds in sesterfisherol biosynthesis (Scheme 1, Scheme 2, and Scheme 3). Based on our DFT calculations, this regioselectivity is determined by the

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• disease [99]. Synthesis of enantiomerically pure (3R,5S)-168 could be accomplished from the aziridine aldehyde (2S,1'R)-6 because the butyrolactone ring formation would proceed with inversion of configuration at C2 in the aziridine ring (Scheme 43) [100]. Thus, condensation of the aldehyde (2S,1'R)-6 with

Synthesis of ([1,2,4]triazolo[4,3-a]pyridin-3-ylmethyl)phosphonates and their benzo derivatives via 5-exo-dig cyclization

• Aleksandr S. Krylov,
• Artem A. Petrosian,
• Julia L. Piterskaya,
• Nataly I. Svintsitskaya and
• Albina V. Dogadina

Beilstein J. Org. Chem. 2019, 15, 1563–1568, doi:10.3762/bjoc.15.159

• -Hydrazinylpyridines (a) and pyridinylhydrazones (b), as well as their acylated derivatives (c), are versatile scaffolds for the preparation of triazolopyridines (Scheme 1). The known methods for the [1,2,4]triazolopyridine ring formation use various condensation agents such as HCOOH, orthoesters, Lawesson’s reagent

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• . Formation of the 1,3-oxazinan-2-one ring. Formation of the product at m/z 382.2765 u. Formation of the components of mixture I. Percent of absorbed guest in the sequestration tests.a Supporting Information Supporting Information File 332: Possible structures of the components present in the mixtures

Protein–protein interactions in bacteria: a promising and challenging avenue towards the discovery of new antibiotics

• Laura Carro

Beilstein J. Org. Chem. 2018, 14, 2881–2896, doi:10.3762/bjoc.14.267

• multiplication and viability of bacteria, and second, they are highly conserved in many bacterial species [85]. Various studies have shown that Z interaction protein A (ZipA) is one of the essential components that stabilize the Z-ring formation and that it binds to FtsZ with high affinity. The interaction

Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

• Gisela V. Saborit,
• Carlos Cativiela,
• Ana I. Jiménez,
• Josep Bonjoch and
• Ben Bradshaw

Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

• stereoselectivity of the ring-formation step can be explained by the suprafacial addition of the allene to the double bond of the α,β-unsaturated compound 4, the diastereoselectivity being sterically controlled by the methyl group on the β-face. The transformation of the vinylsilane moiety in 5 into the

DFT calculations on the mechanism of copper-catalysed tandem arylation–cyclisation reactions of alkynes and diaryliodonium salts

• Tamás Károly Stenczel,
• Ádám Sinai,
• Zoltán Novák and
• András Stirling

Beilstein J. Org. Chem. 2018, 14, 1743–1749, doi:10.3762/bjoc.14.148

• in the order of the oxazoline ring formation and the aryl transfer steps. In our model transformation, it was found that the reaction generally features the aryl transfer–ring closing sequence and this sequence shows very limited sensitivity to the variation of the substituent of the reactants. On

• Scheme 2 and Scheme 3) the ring formation takes place with an activation free barrier of 22.6 kcal/mol (TSrcA). Along this path this is the rate determining step. The calculations revealed that once the ring is formed, the aryl transfer spontaneously occurs and a significant amount of free energy is

• amount free energy to arrive at the same state as postulated for path A. Comparison of the two free energy profiles indicates that the preferred route is the one where the aryl transfer precedes the oxazoline ring formation. On the other hand, the calculated activation free energy barriers are compatible

Recent advances in synthetic approaches for medicinal chemistry of C-nucleosides

• Kartik Temburnikar and
• Katherine L. Seley-Radtke

Beilstein J. Org. Chem. 2018, 14, 772–785, doi:10.3762/bjoc.14.65

• (compound 23) is shown in Figure 9, which involves installing an allyl group at C1' (20) and converting the C2'–CN to an aldehyde (21) followed by a Wittig reaction to install a second allyl group at C2' (22). Second generation Grubb’s catalyst was used for the ring formation, followed by hydrogenation to

A concise flow synthesis of indole-3-carboxylic ester and its derivatisation to an auxin mimic

• Marcus Baumann,
• Ian R. Baxendale and
• Fabien Deplante

Beilstein J. Org. Chem. 2017, 13, 2549–2560, doi:10.3762/bjoc.13.251

• precursors in a multistep sequence prior to indole ring formation [7]. In order to address these potential shortcomings we set out to develop a benign process relying on inexpensive substrates and non-toxic reagents that would rapidly deliver the desired indole in a readily scalable and continuous fashion

• looked at telescoping the final two steps of the process; substitution of the ethoxy group by hydrazine and then ring formation to the 3H-[1,3,4]oxadiazol-2-one unit [32][33]. In this procedure a 0.95 M THF solution of compound 12 was united with a solution of hydrazine (1.0 M in THF) and directed into a

Accessing simply-substituted 4-hydroxytetrahydroisoquinolines via Pomeranz–Fritsch–Bobbitt reaction with non-activated and moderately-activated systems

• Marco Mottinelli,
• Mathew P. Leese and
• Barry V. L. Potter

Beilstein J. Org. Chem. 2017, 13, 1871–1878, doi:10.3762/bjoc.13.182

• -ring formation was investigated in non-activated systems, 5,7,8,13-tetrahydro-6,13-methanodibenzo[c,f]azonine was exclusively obtained. Furthermore, selective ring closure in the para-position could be achieved under standard PFB conditions, while a double ring closure could be obtained utilizing HClO4

• function of the water content of the reaction mixture. An acetal concentration of 0.3 M proved optimal to minimize the ether formation. The PF reaction conditions could possibly lead to a competition between 6-membered and 5-membered ring formation in systems such as 9a,o,p (Scheme 6). For this study

• cyclized into the indole 16p. It is thus possible to infer that indole formation is highly disfavored and only the presence of a great number of activating groups can make this outcome competitive. We then decided to expand our analysis to include competition between 6- and 7-membered ring formation

Photocatalyzed synthesis of isochromanones and isobenzofuranones under batch and flow conditions

• Manuel Anselmo,
• Lisa Moni,
• Hossny Ismail,
• Davide Comoretto,
• Renata Riva and
• Andrea Basso

Beilstein J. Org. Chem. 2017, 13, 1456–1462, doi:10.3762/bjoc.13.143

• , selective synthesis of benzo-fused six- or five-membered rings can be achieved. We have demonstrated that the 5-membered ring formation is favored, when the two processes are competitive, and we have also shown that acetonitrile can act as a third component in the cyclization to oxazepinones. By employing

Studies directed toward the exploitation of vicinal diols in the synthesis of (+)-nebivolol intermediates

• Runjun Devi and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2017, 13, 571–578, doi:10.3762/bjoc.13.56

• formation. Further we speculated that compound 26, in the presence of a base, might undergo a simultaneous epoxidation–intramolecular epoxide-ring opening to produce 27 (Scheme 7) as the corresponding benzoxepin ring formation via intramolecular displacement of –OTs group by ArO− is unresponsive [23]. To

• , may produce traces to significant amounts of side-products via hydrogenolysis. Thus, we decided to modify Panda’s synthetic route to significantly increase the overall yield. We hypothesized that this problem might be circumvented by performing the debenzylation reaction prior to the epoxide-ring

Highly reactive, liquid diacrylamides via synergistic combination of spatially arranged curing moieties

• Maximilian Maier,
• Magnus S. Schmidt,
• Markus Ringwald and
• Christoph P. Fik

Beilstein J. Org. Chem. 2017, 13, 372–383, doi:10.3762/bjoc.13.40

• finger print regime, we can only assume that all three propagation pathways a), b) and c) take place simultaneously. Furthermore, taking in account FTIR and DSC data, we expect that ring formation significantly contributes to the overall reaction enthalpy. It is quite clear, that the combination of

• thus highest apparent network density. This means that ring formation, which in principle should reduce the amount of covalent network points in the cured material, is superimposed by effects of conversion, entanglement and rigidity of the formed polymer. The decreasing trend of flexural modulus from 1

• intramolecular arrangement and the substitution with N-allyl, N-acyl and N-acrylamide functional groups. Surprisingly, the contribution of internal N-allyl groups was higher than that of external ones indicating a dominant, non-classical polymerization mechanism. The results support exothermic ring formation on

Posttranslational isoprenylation of tryptophan in bacteria

• Masahiro Okada,
• Tomotoshi Sugita and
• Ikuro Abe

Beilstein J. Org. Chem. 2017, 13, 338–346, doi:10.3762/bjoc.13.37

• position of its indole ring. Conclusion The posttranslational isoprenylation of tryptophan involving pyrrolidine ring formation was first discovered in a B. subtilis peptide pheromone, as a crucial modification for the pheromonal function. In addition, the discovery of the ComXnatto pheromone revealed that

Biochemical and structural characterisation of the second oxidative crosslinking step during the biosynthesis of the glycopeptide antibiotic A47934

• Veronika Ulrich,
• Clara Brieke and
• Max J. Cryle

Beilstein J. Org. Chem. 2016, 12, 2849–2864, doi:10.3762/bjoc.12.284

• catalysing C-O-D ring formation and that this activity relies on interactions with the non-ribosomal peptide synthetase via the X-domain. Despite the interaction of StaF with the A47934 X-domain being weaker than for the preceding Oxy enzyme StaH, StaF retains higher levels of in vitro activity: we postulate

• show that the substrate specificity of StaF is not as broad as for Oxys catalysing the C-O-D ring formation, in agreement with the results from OxyAtei. Additionally, we could show that StaF interacts with the A47934 X-domain, indicating that StaF is, along with other related Oxy enzymes, recruited by

• appropriate MWCO. 2) Subsequently, the activity assay is performed using StaH and StaF together with the redox system composed of palustrisredoxin reductase (PuR), palustrisredoxin B A105V (PuxB) and NADH, in which StaH catalyses C-O-D ring formation between D-Hpg4 and L-Tyr6 and StaF catalyses ring D-O-E

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• prevent 5-membered ring formation by this group. The cis-dihydroxy groups in position 3 and 4 of compound 2 were acetylated (→ 12) prior to the deprotection of the anomeric center. Following this sequence, allyl 3,4-di-O-acetyl-2-O-methyl-α-L-fucoside (12) was synthesized in 50% yield over four steps from

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• characterised in the pederin (24) and the ambruticin (28) biosynthetic pathways (Scheme 3 and Scheme 4) [14][15]. PedPS7 is a monofunctional pyran synthase (PS) domain that was predicted to catalyse ring formation from an α,β-unsaturated intermediate in the biosynthesis of the PKS–NRPS hybrid product pederin

• polyketide with potent antitumor, antifungal, antiparasitic, pesticidal and antitrypanosomal activities (Scheme 13). In its biosynthesis, the furan-ring formation occurs on a late stage, catalysed in an unprecedented fashion by the cytochrome P450 oxidase AurH [13][62][63][64][65][66][67]. This enzyme