Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• functionalized benzocoumarins to spirocyclic lactones. In 2015, Du and co-workers [74] reported a spirocyclization of diarylacetylenes to fused spiro polycyclic compounds through a hypervalent iodine-mediated cascade annulation reaction. In this reaction, the Lewis acid BF3·Et2O acts as catalyst which activates

Acyl-group specificity of AHL synthases involved in quorum-sensing in Roseobacter group bacteria

• Lisa Ziesche,
• Jan Rinkel,
• Jeroen S. Dickschat and
• Stefan Schulz

Beilstein J. Org. Chem. 2018, 14, 1309–1316, doi:10.3762/bjoc.14.112

• /bjoc.14.112 Abstract N-Acylhomoserine lactones (AHLs) are important bacterial messengers, mediating different bacterial traits by quorum sensing in a cell-density dependent manner. AHLs are also produced by many bacteria of the marine Roseobacter group, which constitutes a large group within the marine

• ; fatty acid composition; N-acylhomoserine lactones; quorum sensing; Phaeobacter inhibens; Introduction The Roseobacter group, a subgroup of the Rhodobacteraceae family, constitutes an important class of Gram-negative marine bacteria, occurring in many different habitats [1][2], in fresh water as well as

• on surfaces [3]. They can produce a variety of secondary metabolites, including antibiotics [4][5], volatile compounds [6][7], oligohydroxybutyrates [8] and a range of N-acylhomoserine lactones (AHLs) [8][9][10]. AHLs are quorum-sensing signaling compounds that are used for cell–cell communication to

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• a high level of enantioselectivity. Naphthol derivatives 31 were converted to spirocyclic lactones 32 in the presence of m-CPBA as co-oxidant for the in situ generation of the I(III) catalyst. Secondary n–π* and/or hydrogen-bonding interactions of the catalyst ensured remarkable enantioselectivities

• ) reagent 9b was used successively for the synthesis of δ-lactones 45 in a highly stereoselective manner starting from 44 [43]. The formation of cyclic iodonium 46 is the vital part of this difunctionalization process. Wirth et al. were the first to introduce asymmetric dioxytosylation of styrene (47) using

• displacement of the aryl iodide by the CO2R group in 77 leading to chiral lactones of type 78 [56]. Rearrangement strategy Wirth et al. used I(III) reagent 8b for the development of a stereoselective oxidative rearrangement method to synthesize α-arylated carbonyls 81 from α,β-unsaturated carbonyls 80 (Scheme

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system

• Toshifumi Dohi,
• Shohei Ueda,
• Kosuke Iwasaki,
• Yusuke Tsunoda,
• Koji Morimoto and
• Yasuyuki Kita

Beilstein J. Org. Chem. 2018, 14, 1087–1094, doi:10.3762/bjoc.14.94

• synthesis of lactones via the intramolecular oxidative cyclization of aryl carboxylic acids at the benzyl carbon under transition-metal-free conditions [52]. Based on our previous research and general interest in the unique reactivity of hypervalent iodine(III)–Br bonds [53][54][55][56], we report the

Preparation, structure, and reactivity of bicyclic benziodazole: a new hypervalent iodine heterocycle

• Akira Yoshimura,
• Michael T. Shea,
• Cody L. Makitalo,
• Melissa E. Jarvi,
• Gregory T. Rohde,
• Akio Saito,
• Mekhman S. Yusubov and
• Viktor V. Zhdankin

Beilstein J. Org. Chem. 2018, 14, 1016–1020, doi:10.3762/bjoc.14.87

• preparation of several bicyclic benziodoxoles 3 starting from 2-iodoisophthalic acid (2, Scheme 1b). These bicyclic benziodoxoles 3 can be used as efficient coupling reagents for the direct condensation reaction between carboxylic acids and alcohols or amines to provide esters, macrocyclic lactones, or amides

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• recycling. Polymeric nanoreactors were also used to perform ring-opening polymerization (ROP) in water. Nallani et al. reported on the enzymatic polymerization of lactones using CalB, which was immobilized in both the polymersome lumen and bi-layer [21]. Nanoreactors for ROP were prepared from polystyrene

Addition of dithi(ol)anylium tetrafluoroborates to α,β-unsaturated ketones

• Yu-Chieh Huang,
• An Nguyen,
• Simone Gräßle,
• Sylvia Vanderheiden,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2018, 14, 515–522, doi:10.3762/bjoc.14.37

• procedure for the synthesis of diene dithioacetals. A similar reaction using α-carbonyl substituted ketene dithioacetals for an addition to alkynes under iron catalysis was shown by Liu et al. before and was used for the synthesis of δ-lactams and lactones by 6-endo annulation [35]. Our approach reveals

The selective electrochemical fluorination of S-alkyl benzothioate and its derivatives

• Shunsuke Kuribayashi,
• Tomoyuki Kurioka,
• Shinsuke Inagi,
• Ho-Jung Lu,
• Biing-Jiun Uang and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2018, 14, 389–396, doi:10.3762/bjoc.14.27

• -(ω-carboxy)alkyl benzothioates afforded intramolecular cyclization products like lactones instead of the corresponding α-fluorinated products. Experimental General information 1H, 13C and 19F NMR spectra were recorded on a JEOL JNM EX-270 (1H: 270 MHz, 13C: 67.8 MHz, 19F: 254.05 MHz) spectrometer in

Diastereoselective Mannich reactions of pseudo-C₂-symmetric glutarimide with activated imines

• Tatsuya Ishikawa,
• Tomoko Kawasaki-Takasuka,
• Toshio Kubota and
• Takashi Yamazaki

Beilstein J. Org. Chem. 2017, 13, 2473–2477, doi:10.3762/bjoc.13.244

• lactones in good to excellent yields [4][5]. One of the most intriguing features of this protocol is the fact that the enantiomers at the lactone part were readily obtained only by the selection of the tertiary amines employed in the reaction. It is quite apparent that this success is, at least in part

Regiodivergent condensation of 5-alkoxycarbonyl-1H-pyrrol-2,3-diones with cyclic ketazinones en route to spirocyclic scaffolds

• Alexey Yu. Dubovtsev,
• Maksim V. Dmitriev,
• Аndrey N. Maslivets and
• Michael Rubin

Beilstein J. Org. Chem. 2017, 13, 2179–2185, doi:10.3762/bjoc.13.218

• tested their reactivity with pyrrolediones 9 (Scheme 6). Gratifyingly, this reasoning was correct, as we obtained the corresponding lactones 23 as the sole products in reasonable yields (Scheme 6). The crystal structure of compound 23aa (CCDC 1546064) depicted in Figure 4 confirmed the formation of this

Are boat transition states likely to occur in Cope rearrangements? A DFT study of the biogenesis of germacranes

• José Enrique Barquera-Lozada and
• Gabriel Cuevas

Beilstein J. Org. Chem. 2017, 13, 1969–1976, doi:10.3762/bjoc.13.192

• possible explanation of the inhibition of Cope rearrangement by the lactone ring (proposed by Takeda) is that the lactone ring raises the Cope TS energy, as the lactone ring strains the germacrane ring. Contrary to what Takeda predicted, the relative energies of opened lactones, TS7-9 (50.8 kcal/mol) and

Pd(OAc)₂/Ph₃P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles

• Dominik Kellner,
• Maximilian Weger,
• Andrea Gini and
• Olga García Mancheño

Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175

• structures that can be further transformed into interesting potential biologically active heterocyclic derivatives such as terpenoid pyranes, lactones, (hydro)chromenes or pyridines, among others [23][24][25][26]. Depending on the connection of the two isoprene units, four different kinds of dimers can be

BODIPY-based fluorescent liposomes with sesquiterpene lactone trilobolide

• Ludmila Škorpilová,
• Silvie Rimpelová,
• Michal Jurášek,
• Miloš Buděšínský,
• Jana Lokajová,
• Roman Effenberg,
• Petr Slepička,
• Tomáš Ruml,
• Eva Kmoníčková,
• Pavel B. Drašar and
• Zdeněk Wimmer

Beilstein J. Org. Chem. 2017, 13, 1316–1324, doi:10.3762/bjoc.13.128

• control of a number of cytokines. Alternatively, lipopolysaccharide (endotoxin) is known as strong inducer of NO in macrophages. Since it is known that sesquiterpene lactones, Tg, Tb, as well as Tb derivatives [31], possess strong stimulating activity for NO production by immune cells [40][41], we

A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE

• Tue Heesgaard Jepsen,
• Emil Glibstrup,
• François Crestey,
• Anders A. Jensen and
• Jesper Langgaard Kristensen

Beilstein J. Org. Chem. 2017, 13, 988–994, doi:10.3762/bjoc.13.98

• synthetic procedures are extremely scarce. Herein, we wish to provide different strategies used to synthesize the CD fragment of DHβE as a general and simple method for the construction of [6,6]-bicyclic lactones which includes a stereoselective synthesis of vinyl halides, a regio- and stereoselective

• unfortunately this reaction proceeded without a trace of the desired lactone 9. Recently Szostak et al. have shown that 6-membered lactones undergo reduction with SmI2 [20] which may explain this result. However, upon treatment with sodium napthalenide lactone 7 was fully converted but all attempts to isolate

• challenging [6,6]-bicyclic lactone fragment in general through an expedient regio- and stereoselective Mizoroki–Heck cyclization approach. This method enabled the synthesis of the elusive and volatile CD fragments ([6,6]-bicyclic lactones 9 and 26) of the Erythrina alkaloid DHβE. This allowed the

Synthesis of D-manno-heptulose via a cascade aldol/hemiketalization reaction

• Yan Chen,
• Xiaoman Wang,
• Junchang Wang and
• You Yang

Beilstein J. Org. Chem. 2017, 13, 795–799, doi:10.3762/bjoc.13.79

• chain elongations of aldoses employing the Henry reaction, the aldol reaction, and the Wittig reaction for the preparation of ketoheptoses [20][21][22], sugar lactones were also often utilized for the synthesis of D-manno-heptulose via reactions with C-nucleophiles or conversion into exocyclic glycals

Lipids: fatty acids and derivatives, polyketides and isoprenoids

• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2017, 13, 793–794, doi:10.3762/bjoc.13.78

• another important consequence for signaling compounds that travel with high speed in aqueous environments – an effect that is immediately recognizable if a drop of oil is spilled on a water surface. An impressive example is reported in this Thematic Series with the use of highly apolar lactones from the

Phosphazene-catalyzed desymmetrization of cyclohexadienones by dithiane addition

• Matthew A. Horwitz,
• Elisabetta Massolo and
• Jeffrey S. Johnson

Beilstein J. Org. Chem. 2017, 13, 762–767, doi:10.3762/bjoc.13.75

• nucleophile. Mild reaction conditions allow the formation of diversely functionalized fused bicyclic lactones. The products participate in facially selective additions from the convex surface, leading to allylic alcohol derivatives. Keywords: conjugate addition; cyclohexadienones; dearomatization

• desymmetrizing intramolecular conjugate addition of a tethered dithiane moiety to para-cresol-derived cyclohexadienones. The substrates are easily accessible from cheap starting materials and the reaction provides functionalized bicyclic lactones as a single diastereomer. The products of the reaction were able

Exploring endoperoxides as a new entry for the synthesis of branched azasugars

• Svenja Domeyer,
• Mark Bjerregaard,
• Henrik Johansson and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2017, 13, 644–647, doi:10.3762/bjoc.13.63

• ready access to the two lactol isomers 29,30 in quantitative yield (≈1:1 ratio of isomers) [10][22][23]. Lactol isomers 29,30 could potentially serve as precursors for the formation of substituted piperidines via reductive amination or be oxidised to yield lactones or lactam derivatives. Conclusion

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• unepimerized methyl configuration) to generate a hybrid PKS called TKS-AR1, and the stereochemistry of the resulting triketide lactones 15 and 16 established by NMR. This analysis showed that the methyl group arising from the hybrid 1/5 module was epimerized in 50% of the product 16 and that this change in

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

• isoprenyl side chain is an influential factor of the group- (or species-) specific pheromonal activity [25]. Intriguingly, the same applies for group- (or species-) specificity in Gram negative bacteria because the chemical structure and length of the acyl side chain in acylhomoserine lactones, which are

• in boldface and colored blue. (B) Chemical structures of acyl homoserine lactones. The acyl side chains are shown in boldface. (A) Schematic representation of the signal transduction cascade of quorum sensing stimulated by the ComX pheromone in B. subtilis. (B) Amino acid sequences of the aspartate

The reductive decyanation reaction: an overview and recent developments

• Jean-Marc R. Mattalia

Beilstein J. Org. Chem. 2017, 13, 267–284, doi:10.3762/bjoc.13.30

• monodecyanated products 69a,b. Bicyclic lactones 70a,b are then obtained in 3 steps in 41% and 51% yields, respectively, from 69a,b. Later Curran’s group discovered that NHC-boryl radicals, generated from NHC-boranes (N-heterocyclic carbene boranes), abstracted the cyano group from various organic nitriles and

• [106]. Synthesis of bicyclic lactones [119][120]. Reductive decyanation of malononitriles and cyanoacetates using NHC-boryl radicals (9 examples). For 74 and 75, isolated or NMR yields are given from 71 [121]. Proposed mechanism for the reduction by NHC-boryl radicals. The other possible pathway

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• , is usually not possible from an EI mass spectrum. In the article, we present the synthesis and for the first time elucidate the structure of macrolides from the frog family Hyperoliidae. Keywords: chemical communication; chiral gas chromatography; macrocyclic lactones; ring-closing metathesis

• ; pheromones; Introduction The lactone motif is found in many compounds that are used in chemical communication. Among them, macrocyclic lactones are an important class because of their biosynthetic availability and their inherent compound properties. During the biosynthesis of macrocyclic lactones, a fatty

• from Madagascar also use chemical cues. Macrocyclic lactones such as phoracantholide I (3), phoracantholide J (4) or gephyromantolide A (5), are released by males from femoral glands to serve as signals, often accompanied by secondary alcohols (Figure 1) [2][3][4]. Another frog family most likely using

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• supramolecular polymerization catalyst capable of inserting the monomer between the active and binding sites can be designed. Based on this concept, we have reported that CDs can include and activate lactones to yield a polymer with a single CD at the end of the polymer chain [61][62][63][64]. Subsequently, we

Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase

• Hui Hong,
• Yuhui Sun,
• Yongjun Zhou,
• Emily Stephens,
• Markiyan Samborskyy and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2016, 12, 2164–2172, doi:10.3762/bjoc.12.206

• or module of enzymes. Examples of deviation from this paradigm, in which a module catalyses either multiple extensions or none are of interest from both a mechanistic and an evolutionary viewpoint. We present evidence that in the biosynthesis of the 36-membered macrocyclic aminopolyol lactones

• iteration on the first extension module of the PKS for the marginolactone azalomycin. Given the identical gene arrangement in the kanchanamycin gene cluster, we propose that iteration also operates there. The structures of marginolactones azalomycin and kanchanamycin, and of the β-lactones ebelactone A and