Solid-state studies and antioxidant properties of the γ-cyclodextrin·fisetin inclusion compound

• Joana M. Pais,
• Maria João Barroca,
• Maria Paula M. Marques,
• Filipe A. Almeida Paz and
• Susana S. Braga

Beilstein J. Org. Chem. 2017, 13, 2138–2145, doi:10.3762/bjoc.13.212

• their mass. This allows observing processes of dehydration, sublimation and decomposition [36]. The traces of γ-CD, fisetin, their 1:1 physical mixture and the γ-CD·fisetin inclusion compound are depicted in Figure 3. As can be seen from the TGA trace for fisetin no mass losses are observed between

• TG trace of the γ-CD·fisetin inclusion compound, that is, decomposition of the guest is not observed. The most striking difference between the trace of the inclusion compound and that of the physical mixture is observed in the dehydration profile. The mass loss from dehydration in γ-CD·fisetin is

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

• yield of the cyclic ether was still low (Table 2, entry 6). Microwave heating was not helpful (Table 2, entry 7). The non-nucleophilic base DBU was not effective in promoting the cyclization, either (Table 2, entry 8). We observed small amounts of products arising from the dehydration of 15 in the 1H

Iodoarene-catalyzed cyclizations of N-propargylamides and β-amidoketones: synthesis of 2-oxazolines

• Somaia Kamouka and
• Wesley J. Moran

Beilstein J. Org. Chem. 2017, 13, 1823–1827, doi:10.3762/bjoc.13.177

• -oxazolines, which are valuable heterocycles found in ligand scaffolds, natural products such as the leupyrrins [18][19], and potential pharmaceuticals (Figure 1) [20][21][22]. Traditional routes to this heterocycle include the dehydration of amino alcohols with carboxylic acids, however, this process

Aqueous semisynthesis of C-glycoside glycamines from agarose

• Juliana C. Cunico Dallagnol,
• Alexandre Orsato,
• Diogo R. B. Ducatti,
• Miguel D. Noseda,
• Maria Eugênia R. Duarte and
• Alan G. Gonçalves

Beilstein J. Org. Chem. 2017, 13, 1222–1229, doi:10.3762/bjoc.13.121

• presents a hydroxy and an aldehyde hydrate group. Yet obtaining this type of product is not an easy task because of its acid liability. Hydrolysis conditions must be mild to avoid dehydration leading to hydroxymethyl furaldehyde byproduct [22]. The crude agarose hydrolysate containing 2 was then directly

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• materials were obtained when the team used sucrose or starch as starting carbohydrate materials. In addition to microwave and acid reflux-mediated glucose dehydration reactions, the group of Wang developed an alternative protocol that combined glucose with monopotassium phosphate (KH2PO4) in a Teflon-lined

• ). In the absence of KH2PO4, irregular black carbon aggregates were obtained. Raman and TEM analysis showed both types of FCDs had graphitic crystallinity. This example highlights that an inorganic-based dehydrating agent could be used instead of a traditional diamine SPA to induce CD dehydration and

• improved materials with high QYs. Non-glucose monosaccharide-based fluorescent carbon dots In addition to glucose, different monosaccharides and polyols have also been utilised as carbon sources for the synthesis of FCD, although this approach is less common. The ability of glycerol to undergo dehydration

Isoxazole derivatives as new nitric oxide elicitors in plants

• Anca Oancea,
• Emilian Georgescu,
• Florentina Georgescu,
• Alina Nicolescu,
• Elena Iulia Oprita,
• Catalina Tudora,
• Lucian Vladulescu,
• Marius-Constantin Vladulescu,
• Florin Oancea and
• Calin Deleanu

Beilstein J. Org. Chem. 2017, 13, 659–664, doi:10.3762/bjoc.13.65

• situ by the oxidative dehydrogenation of aldoximes in the presence of various oxidants [26][27][28][29], or by the dehydrohalogenation of hydroxyiminoyl halides promoted by organic or inorganic bases [30][31][32]. A less used synthetic procedure involves the oxidative dehydration of primary nitro

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• , next alkenylrhodium 165 were formed as intermediates as a result of dehydration and β-H elimination followed by hydrorhodation, respectively. Then, rhodium 1,4-migration, alkylrhodation and finally rhodium elimination led to 1-indanones 162 via intermediates 166 and 167. Abicoviromycin (168) is an

• receptor modulator, 3-[4-(1-piperidinoethoxy)phenyl]spiro[indene-1,1’-indane]-5,5’-diol hydrochloride (216) which may be used for a new treatment of hot flush [88]. In this synthesis, the reaction of 5-methoxyindan-1-one (212) with the Grignard reagent 217 followed by acid-catalyzed dehydration and

• 276 [106]. The new catalytic reaction which replaced a previously described four-step synthesis [107], involved a tandem aldol condensation/dehydration and cyclization of the intermediate 275 to 276 (Scheme 77). In 1999, Ikeda and Mori have presented a cyclotrimerization of enones (e.g

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

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

• introduced primarily by methyl transferase domains [18], with presumably defined the stereospecificity (the stereochemistry is not always evident, as it can be obscured by subsequent dehydration). The suite of processing reactions also introduces stereochemistry into the molecules: the hydroxy groups

• resulting from ketoreduction of the initially-formed C-3-ketones exhibit both configurations, dehydration of the hydroxy functionality generates both cis- and trans-double bonds, and finally, enoyl reduction can produce both configurations at the saturated C2-methyl centers. Other types of processing

• this proposal, the KRs ultimately determine whether or not dehydration can occur (it should not occur for intermediates in which the C-2 methyl is epimerized, because the C-2 proton is inaccessible to the DH catalytic apparatus) and the stereochemistry of the resulting double bonds (via A- or B-type

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• increased, the amount of 10 increased. When the parameter space was explored using the self-optimisation approach the selectivity to 10 was increased to 63%. The etherification/deamination pathway forming 9 could not be optimised above 11% as the dehydration or methylated products were present as the major

Revaluation of biomass-derived furfuryl alcohol derivatives for the synthesis of carbocyclic nucleoside phosphonate analogues

• Bemba Sidi Mohamed,
• Christian Périgaud and
• Christophe Mathé

Beilstein J. Org. Chem. 2017, 13, 251–256, doi:10.3762/bjoc.13.28

• catalytic hydrogenation of furfural; the latter is obtained from the dehydration of xylose, a 5-carbon sugar derived from vegetal biomass. Furfuryl alcohol finds widespread application in the chemical industries and for example is employed for the production of synthetic fibers, fine chemicals, etc. In fine

New approaches to organocatalysis based on C–H and C–X bonding for electrophilic substrate activation

• Pavel Nagorny and
• Zhankui Sun

Beilstein J. Org. Chem. 2016, 12, 2834–2848, doi:10.3762/bjoc.12.283

• directionality that might make these interactions of a great value to the field of organocatalysis [71][72][73]. Molecular iodine has been used for many decades as a mild catalyst or promoter of various organic transformations such as conjugate addition, imine formation or aldolate dehydration reactions [74][75

cis-Diastereoselective synthesis of chroman-fused tetralins as B-ring-modified analogues of brazilin

• Dimpee Gogoi,
• Runjun Devi,
• Pallab Pahari,
• Bipul Sarma and
• Sajal Kumar Das

Beilstein J. Org. Chem. 2016, 12, 2816–2822, doi:10.3762/bjoc.12.280

• acids was used as the key step. Our worries concerning the formation of cis–trans product mixtures and their probable conversion to naphthopyran derivatives via dehydration of the tertiary hydroxy group were laid to rest. Additionally, the angular hydroxy group of one of the synthesized products has

• group of 5 and/or 9, leading to the formation of a stable 3°carbocation that can undergo further dehydration reactions until full aromatization to the naphthalene ring is achieved. This study would serve to help us to find the real scenario. Finally, in the presence of Lewis/Brønsted acids, substrates 6

• mixture of 6a,7,8,12b-tetrahydro-6H-naphtho[2,1-c]chromen-6a-ols and their probable conversion to of naphthopyran derivatives via dehydration of tertiary –OH group were laid to rest. To the best of our knowledge, this is the first example of the generation of such type of chroman-fused tetralins. The easy

Computational methods in drug discovery

• Sumudu P. Leelananda and
• Steffen Lindert

Beilstein J. Org. Chem. 2016, 12, 2694–2718, doi:10.3762/bjoc.12.267

• [123]. Here the binding energy of a target–ligand complex is solely estimated by a hydrogen bond term and a dehydration energy term. ChemScore [122] and SCORE [124] are two other scoring functions that are also empirical. Consensus-based scoring functions Current scoring functions are not perfect and

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• enzyme mppR is a pyruvate aldose that catalyses the dehydration/cyclisation of 20 to give cyclic guanidine 21 [52], where transamination by mppQ gives enduracididine (1). Further transformation to L-β-hydroxyenduracididine (5) is then catalysed by mppO [52][53]. Synthetic investigations Synthesis of

Isosorbide and dimethyl carbonate: a green match

• Fabio Aricò and
• Pietro Tundo

Beilstein J. Org. Chem. 2016, 12, 2256–2266, doi:10.3762/bjoc.12.218

• isosorbide with green reagents and solvent dimethyl carbonate (DMC) is reported. Dehydration of D-sorbitol via DMC in the presence of catalytic amounts of base is an efficient and viable process for the preparation of the industrially relevant anhydro sugar isosorbide. This procedure is “chlorine-free”, one

• terms of sustainability, applications and market value. In fact, dehydration of D-sorbitol (Scheme 1) produces anhydro sugar alcohols, including sorbitan (mono-anhydrosorbitol) and isosorbide (dianhydrosorbitol). Both these products have achieved commercial importance and can be used to synthesize

• glucose via biotechnological and chemocatalytic depolymerization of polysaccharides. The conversion of D-sorbitol into isosorbide via sorbitan is then usually performed by a twofold dehydration reaction using different types of catalysts (Scheme 1) [49][50][51][52][53][54][55][56][57][58][59][60]. In 1968

TBHP-mediated highly efficient dehydrogenative cross-oxidative coupling of methylarenes with acetanilides

• Cui Chen,
• Weibing Liu and
• Peng Zhou

Beilstein J. Org. Chem. 2016, 12, 2250–2255, doi:10.3762/bjoc.12.217

• the control experiments, intermediate 6 also could be obtained from the reaction of benzaldehyde with 2a under the standard conditions. Then, intermediate 6 underwent a sequence of steps including fast oxidation and dehydration to give N-acetyl-N-phenylbenzamide (8) under the stipulated conditions

Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products

• Dmitry S. Ryabukhin,
• Dmitry N. Zakusilo,
• Mikhail O. Kompanets,
• Anton A.Tarakanov,
• Irina A. Boyarskaya,
• Tatiana O. Artamonova,
• Mikhail A. Khohodorkovskiy,
• Iosyp O. Opeida and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 2125–2135, doi:10.3762/bjoc.12.202

• protonation of the carbonyl oxygen and hydroxy group of 5-HMF (1a) in strong acids gives rise to cationic species A, the dehydration of the latter may result in the formation of heteroaromatic benzyl-type dication B (Scheme 1). Protonation of the aldehyde groups in 2,5-DFF (2) leads to cation C and dication D

• . This means that dehydration of this group does not occur in TfOH and cation B is not formed. For comparison, chemical shifts of carbocationic centers in various benzyl cations (R2)ArC+ lie in a much more down-field range of ~182–270 ppm [50][51][52][53][54][55][56][57]. Comparison of 1H and 13C NMR

Solvent-free synthesis of novel para-menthane-3,8-diol ester derivatives from citronellal using a polymer-supported scandium triflate catalyst

• Lubabalo Mafu,
• Ben Zeelie and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 2046–2054, doi:10.3762/bjoc.12.193

• the acylation reaction with acid anhydrides (Scheme 3). It needs to be clarified that earlier attempts to perform classic esterifications by reaction of the alcohols with a carboxylic acid were not particularly successful, as very complex reaction mixtures were produced as a result of dehydration of

• presentation of PMD 3 conversion to the desired product at various temperatures. It can be seen on the graph in Figure 1 that the PMD 3 conversion to diesters has its optimum at lower temperatures. When the reaction is operated at 70 °C and above, dehydration of the substrate starts to occur, leading to

• any dehydration or mono acetate 13 formation. Effect of molar ratio The effects of the molar ratio toward the conversion of 3 and the selectivity for 9 were further evaluated at the optimum conditions as highlighted above. The acetic anhydride to para-menthane-3,8-diol molar ratio ranging from 2 to 6

Microwave-assisted cyclizations promoted by polyphosphoric acid esters: a general method for 1-aryl-2-iminoazacycloalkanes

• Jimena E. Díaz,
• María C. Mollo and
• Liliana R. Orelli

Beilstein J. Org. Chem. 2016, 12, 2026–2031, doi:10.3762/bjoc.12.190

• acid type. They have been widely used for several synthetically useful transformations like dehydration of amides leading to nitriles [23][24] or the Beckmann rearrangement [23][25]. They have also been employed in the synthesis of heterocycles such as benzimidazoles, benzothiazoles, benzoxazoles [23

• heterocycles. In this case no dehydration would be involved and PPA esters, due to their Lewis acid nature, would solely increase the electrophilicity of the cyano group towards an intramolecular nucleophilic attack. This approach would avoid the use of strong protic acids, which may be disadvantageous for

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

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

• to a histidine or an asparagine residue in their active site. This exchange avoids the dehydration reaction and might facilitate the activation of the hydroxy group for nucleophilic attack on the Michael system by proton abstraction. PS domains also form a distinct phylogenetic clade compared to DH

• domains. Within a module, PS domains are usually located adjacent to DH domains and act on their transiently formed dehydration product [14]. The arrangement is somewhat different in the case of AmbDH3 from ambruticin biosynthesis (Scheme 4) [15]. This bifunctional domain catalyses both steps, dehydration

• of a 3-hydroxythioester intermediate 25 and subsequent cyclisation to a tetrahydropyran ring 27. AmbDH3 is currently the only known case of a pyran-forming domain in a cis-AT PKS. Hahn et al. showed that AmbDH3 catalyses dehydration of only the 2-D,3-D-configured precursor 25 to the E-configured

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• residues [47][48][49]. Lanthipeptides are divided into four distinct classes (I–IV) based on the differences between the biosynthetic enzymes that carry out dehydration and cyclisation [44]. Dehydration in class I lanthipeptide pathways is catalysed by a LanB dehydratase (NisB for nisin) and cyclisation is

• precursor peptide NisA showed that dehydration involves the glutamylation of Ser and Thr side chains prior to elimination of glutamate [50]. This mechanistic proposal was established due to the observation that three NisB mutants (R786A, R826A and H961A) were able to transfer multiple glutamates to NisA

• aminoacyl-tRNA may actually be common across nature. Interestingly, a subset of these proteins lack the elimination domain and are commonly associated with NRPSs rather than RiPPs, but the function of these small LanBs is not yet known [52][53]. In contrast to class I lanthipeptides, both dehydration and

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• phenols, the reactions exclusively gave the para-substituted products. Mechanistically, in the presence of a catalytic amount of Lewis acid, the 3-hydroxyoxindole was converted to the intermediate A through dehydration, which was then tapped by the electron-rich phenol. para-Substituted products were

Scope and mechanism of the highly stereoselective metal-mediated domino aldol reactions of enolates with aldehydes

• M. Emin Cinar,
• Bernward Engelen,
• Martin Panthöfer,
• Hans-Jörg Deiseroth,
• Jens Schlirf and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 813–824, doi:10.3762/bjoc.12.80

• temperature, the condensation product 6ac emerges from the dehydration of 6a, taking place via an irreversible reaction, which is accountable for the decrease of the yield at higher temperatures. The mechanism depicted in Scheme 6 is in agreement with the following set of requirements with regard to the metal

Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins

• Guozheng Huang,
• Simon Schramm,
• Jörg Heilmann,
• David Biedermann,
• Vladimír Křen and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 662–669, doi:10.3762/bjoc.12.66

• , Prague 4, CZ-14220, Czech Republic 10.3762/bjoc.12.66 Abstract Various Mitsunobu conditions were investigated for a series of flavonolignans (silybin A, silybin B, isosilybin A, and silychristin A) to achieve either selective esterification in position C-23 or dehydration in a one-pot reaction yielding

• the biologically important enantiomers of hydnocarpin D, hydnocarpin and isohydnocarpin, respectively. This represents the only one-pot semi-synthetic method to access these flavonolignans in high yields. Keywords: dehydration; flavonoid; hydnocarpin; Mitsunobu; silybin; Introduction Flavonolignans

• alcohols and bulky acids: Cherney and Wang observed an elimination of a serine derivative during esterification experiments [23]. During conversion of substituted benzyl alcohols to amines under Mitsunobu conditions, elimination also occurred [24]. Dehydration under Mitsunobu conditions has been applied in