Recent developments in the engineered biosynthesis of fungal meroterpenoids

• Zhiyang Quan and
• Takayoshi Awakawa

Beilstein J. Org. Chem. 2024, 20, 578–588, doi:10.3762/bjoc.20.50

• meroterpenoids: insuetusin A1 (12) and insuetusin B1 (10), respectively (Figure 2) [9]. Like other Trt1-type enzymes, InsB2 catalyzes the protonation of the epoxide, the formation of two six-membered rings in a chair–chair conformation, but the reaction finishes with the deprotonation of the hydroxy group at C-3

Unveiling the regioselectivity of rhodium(I)-catalyzed [2 + 2 + 2] cycloaddition reactions for open-cage C₇₀ production

• Cristina Castanyer,
• Anna Pla-Quintana,
• Anna Roglans,
• Albert Artigas and
• Miquel Solà

Beilstein J. Org. Chem. 2024, 20, 272–279, doi:10.3762/bjoc.20.28

• reaction between diynes and C60, followed by a cage-opening through a Rh‐catalyzed di‐π‐methane rearrangement (Scheme 1). It is well-known that [6,6]-bonds (the bonds at the junction between two six-membered rings, Figure 1, left) are more reactive than [5,6]-bonds in C60 [36][37][38], and, not

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• these motifs have attracted considerable interest. The synthesis of azapolycycles containing a seven-membered carbocyclic ring is particularly challenging in contrast to comparable skeletons containing only five- or six-membered rings [3]. Thus, comparatively few general methods exist for accessing

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• “in” complexes. These are amines in which the size of the alkyl groups does not exceed the size of the ethyl group and cyclic sec-amines with five and six-membered rings. Pyrrolidine is the sec-amine that is most “structurally matched” to the size of the R[4]A cavity. For amines with longer alkyl

Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series

• Cécile Alleman,
• Charlène Gadais,
• Laurent Legentil and
• François-Hugues Porée

Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23

• synthesis of five- and six-membered rings can be readily achieved through ring-closing metathesis (RCM), but the synthesis of eight-membered rings has been carried out later [13][14]. In this part, we will focus on the use of RCM to achieve total syntheses of natural products or to access the carbon

Improving the accuracy of ³¹P NMR chemical shift calculations by use of scaling methods

• William H. Hersh and
• Tsz-Yeung Chan

Beilstein J. Org. Chem. 2023, 19, 36–56, doi:10.3762/bjoc.19.4

• . Conformational differences play a role here, particularly for the six-membered rings in compounds 15–18, where the twist boat conformations can be the major isomers in solution [74] (see Table 3 footnotes and Supporting Information File 1 for details), although care was taken to find all important conformations

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• Hg(TFA)2 then five- and six-membered rings 64 and 65 were formed with a 1:4 ratio (Scheme 22) [70]. The greater yield of the six-membered product was primarily due to the electron-withdrawing effect of ethereal oxygen which in turn destabilizes the carbocation at the β-carbon and hence the

• terminus, whereas six-membered rings (111a,b) formed predominantly in case of unsubstituted alkyne dithioacetals (Scheme 33) [86]. They had reported the plausible mechanism for the formation of a six-membered pyranose ring follows ‘path a,' while for the formation of five-membered pyrrolidine derivatives

• )2-catalyzed hydroxylative carbocyclization of 1,6-enyne 156 (Scheme 45) [104]. It was observed that from 1,7-enynes, six-membered rings were formed in low to moderate yield while from 1,8-enynes, uncyclized hydrated products were isolated. as major products along with different byproducts. In a Hg

Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances

• Thiago S. Silva and
• Fernando Coelho

Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112

• good yields. Five- and six-membered rings were synthesized by this method, and the tetracyclic compounds 69i–l were obtained when isopregol halide derivatives were employed. No diastereoselectivity was observed in the five-membered cyclizations (Scheme 26A, 69e–g), whereas the six-membered ring 69h was

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• reactions with seven-membered cyclic enones. However, the effectiveness was decreased in the case of five-membered rings or heterocyclic six-membered rings as the substrates (Table 14) [44]. The unsatisfactory result obtained for substrate B (entry 10, Table 14) was overcome in the next work that focused on

Stereoselective syntheses of 3-aminocyclooctanetriols and halocyclooctanetriols

• Emine Salamci and
• Yunus Zozik

Beilstein J. Org. Chem. 2021, 17, 705–710, doi:10.3762/bjoc.17.59

• inhibitors of α-glycosidases [11][19]. Recent reviews report on the latest synthetic methodologies for aminocyclitols and related compounds [1][2][3][16]. Many methods have been previously reported for the synthesis of aminocyclitols containing five- and six-membered rings, along with their diverse

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• -membered rings of C60 were calculated to be 3.541 and 3.702 Å, respectively. These results suggest significant host–guest π–π interactions between TBTQ-(OG)6 and C60 [57]. In order to intuitively assess the hydrophilicity and hydrophobicity of the complex, the hydrophobic surface diagram was generated and

• -fullerene can be embedded between the six arms of TBTQ-(OG)6 and the distance between the center of one benzene ring of the host and the closest five-membered ring of the guest was calculated to be 3.224 Å. The distances between the center of a triazole ring of TBTQ-(OG)6 and the adjacent five and six

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and ⁶Li/¹³C NMR spectroscopic data

• Jürgen Vollhardt,
• Hans Jörg Lindner and
• Hans-Joachim Gais

Beilstein J. Org. Chem. 2020, 16, 2057–2063, doi:10.3762/bjoc.16.172

• four-membered rings, while two lithium atoms, a sulfur atom, and three oxygen atoms form two six-membered rings. Because of the presence of C–Li and O–Li bonds in (2a)4·(THF)6, the dicarbanions are both C,C- and O,Li-dilithiated species. The C–Li, C–S, and O–Li bond lengths (Table 1) of the tetramer

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• attractive because the reagents involved in the reaction process are simple and inexpensive, plus they only require molecular oxygen or air. In addition, disulfide-catalyzed cyclization reactions are also very effective for the generation of five- and six-membered rings. The unique high selectivity and

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• from the oxymethine H-25 to C-1 established a macrolactone structure, and a spiroacetal structure with two six-membered rings was deduced from a series of HMBC correlations of the protons in the spiro rings to C-27, illustrating the oligomycin-class structure. The remaining six carbons from C-42 to C

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• annulation was favorable for the formation of six-membered rings. Nevertheless, the existence of several rotamers of 1 derived from the restricted rotation of the peripheral phenyl ring substituents and its nonplanar geometry prevented the structure elucidation by proton NMR analysis [35]. Single crystals of

Palladium-catalyzed synthesis and nucleotide pyrophosphatase inhibition of benzo[4,5]furo[3,2-b]indoles

• Hoang Huy Do,
• Saif Ullah,
• Alexander Villinger,
• Joanna Lecka,
• Jean Sévigny,
• Peter Ehlers,
• Jamshed Iqbal and
• Peter Langer

Beilstein J. Org. Chem. 2019, 15, 2830–2839, doi:10.3762/bjoc.15.276

• was noticed that both five and six-membered rings of the benzofuran moiety were linked via π–π stacked relation with His483. However, the aromatic ring of indole demonstrated π–alkyl bonding by Leu239. The additional π–anion interaction was observed with the phosphate group and benzofuran. The 3D

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• hormonal ones. All steroids are based on a common skeleton containing three fused six-membered rings and one five membered ring. This fused-ring system provides a readily available source of rigidity and chirality, whose substituents can be oriented either towards the α- or the β-face. Steroids feature a

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• : asymmetric organocatalysis; axial chirality; biaryls; hydrogen bond; oxo-Diels–Alder reaction; Introduction The Diels–Alder (DA) reaction is a useful and easy-to-perform method for the synthesis of six-membered rings through the direct formation of C–C bonds between a diene and a dienophile (a substituted

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• manifests in six-membered rings when 1JC–Hax < 1JC–Heq [8][9]. A similar effect on 1JC–F has been observed on fluorinated six-membered rings and then called the (reverse) fluorine Perlin-like effect [10]. Despite some controversies on the origin of such effects [11][12][13][14], the anomeric-like

Synthesis, biophysical properties, and RNase H activity of 6’-difluoro[4.3.0]bicyclo-DNA

• Sibylle Frei,
• Adam K. Katolik and
• Christian J. Leumann

Beilstein J. Org. Chem. 2019, 15, 79–88, doi:10.3762/bjoc.15.9

• obtained crystal structure of derivative 6 (Table S1, Supporting Information File 1). The reason for that can be attributed to the different conformations of the six-membered rings in these two structures. Apart from that, the two structures were very similar. Synthesis of the modified oligonucleotides and

Ring-closing-metathesis-based synthesis of annellated coumarins from 8-allylcoumarins

• Christiane Schultze and
• Bernd Schmidt

Beilstein J. Org. Chem. 2018, 14, 2991–2998, doi:10.3762/bjoc.14.278

• which a heterocycle is annellated to the benzene ring of the coumarin skeleton. In particular the latter group is often further divided into sections according to ring size (five-membered rings: furanocoumarins; six-membered rings: pyranocoumarins) and location of the annellated ring (linear vs angular

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• Cyclization by anodic oxidation In initial experiments, the electrochemical behavior of the methyl-substituted derivative bearing six-membered rings (sDTE66-Me) was investigated. For both configurational isomers, i.e., E- and Z-sDTE66-Me, an irreversible oxidation wave corresponding to the transfer of two

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• to form a five-membered metallacycle, subtending N(2)–Ni(1)–N(3) and N(5)–Ni(2)–N(6) angles of 81.53° and 80.34°, respectively. Additionally, the nitrogen atoms on the oxazoline and amide moieties form six-membered rings with the nickel(ΙΙ) center with N(1)–Ni(1)–N(2) and N(4)–Ni(2)–N(5) angles of

• °, respectively. The coordination of the nitrogen atoms on oxazoline and amide moieties with the two zinc centers forms six-membered rings with N(3)–Zn(1)–N(2) and N(6)–Zn(2)–N(5) angles of 87.05° and 88.55°, respectively. All of the Zn–N distances are within 2.023–2.177 Å, as expected for such complexes

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• with similar intramolecular etherifications to make five- and six-membered rings [40], and our own preparation of an analogous seven-membered cyclic ether [41], we examined Pd(0) catalyst precursors with the Q-Phos ligand. The reaction with Pd(dba)2 with Q-Phos and sodium tert-butoxide produced cyclic

Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience

• Serge Pérez and
• Daniele de Sanctis

Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114

• and six membered rings, anomeric mixture, etc.). It is also true that much less effort has been devoted to the production of organic crystals of medium sized biomolecules compared to biological macromolecules. Nevertheless, in many instances, ordered samples may be obtained, either in the form of