Synthesis of zearalenone-16-β,D-glucoside and zearalenone-16-sulfate: A tale of protecting resorcylic acid lactones for regiocontrolled conjugation

• Hannes Mikula,
• Julia Weber,
• Dennis Svatunek,
• Philipp Skrinjar,
• Gerhard Adam,
• Rudolf Krska,
• Christian Hametner and
• Johannes Fröhlich

Beilstein J. Org. Chem. 2014, 10, 1129–1134, doi:10.3762/bjoc.10.112

• rather harsh unfavorable demethylation with boron tribromide in the last step [26]. Without structure verification and characterization ZEN-16-β,D-glucoside (7, Figure 2B) was tentatively identified as a byproduct of the Königs–Knorr glucosylation of ZEN for preparation of ZEN-14-glucoside [27]. In the

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

• G. Gangadhararao,
• Ramesh Kotikalapudi,
• M. Nagarjuna Reddy and
• K. C. Kumara Swamy

Beilstein J. Org. Chem. 2014, 10, 996–1005, doi:10.3762/bjoc.10.99

• believed to proceed by the initial interaction of H+ with the α,β-allenic double bond to lead to V (Scheme 8) which on subsequent attack of oxygen of the ester group onto the β-position of allene forms VI. Intermediate VI on demethylation leads to phosphinoylisocoumarin VII. This product VII further

Synthesis of novel derivatives of 5-hydroxymethylcytosine and 5-formylcytosine as tools for epigenetics

• Anna Chentsova,
• Era Kapourani and
• Athanassios Giannis

Beilstein J. Org. Chem. 2014, 10, 7–11, doi:10.3762/bjoc.10.2

• (5hmC) and 5-formylcytosine (5fC) derivatives that can be used as tools in the emerging field of epigenetics for deciphering chemical biology of TET-mediated processes. Keywords: 3,6-dihydrodeoxycytidine derivatives; DNA demethylation; epigenetics; 5-hydroxymethylcytosine (5hmC) derivatives; TET

• is a densely studied field, its reverse process has not yet been deciphered. In trying to understand DNA demethylation several mechanisms involving new cytosine-modified bases as intermediates have been proposed (Scheme 1). (1) The most widely accepted pathway includes iterative oxidation of 5mC

• ) machinery [15][16][17][21]. (3) Among other putative demethylation mechanisms is the direct dehydroxymethylation of 5hmC to cytosine by action of DNA methyltransferases (DNMT). This enzymatic process was observed in vitro, whether it also works in vivo is yet to be elucidated [15][22]. (4) Lastly

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• substituted Grignard reagent 1.26. A Friedel–Crafts type acylation promoted by either triflic acid or polyphosphoric acid (PPA) furnishes the tricyclic structure 1.28 which upon N-demethylation affords clarinex (1.22). One of the top-selling classes of pharmaceuticals containing the pyridine ring are the

• moderate yield the benzoxazine 1.118; via the imine intermediate. This material can then be condensed with diethyl ethoxymethylenemalonate (1.123), and further cyclised via an intramolecular Friedel–Crafts acylation promoted by polyphosphate. Aluminium tribromide assisted demethylation of the pendant

Selective copper(II) acetate and potassium iodide catalyzed oxidation of aminals to dihydroquinazoline and quinazolinone alkaloids

• Matthew T. Richers,
• Chenfei Zhao and
• Daniel Seidel

Beilstein J. Org. Chem. 2013, 9, 1194–1201, doi:10.3762/bjoc.9.135

• , deoxyvasicinone (4) was obtained as the major product in a process that involved demethylation (Scheme 1, reaction 1). The demethylation of aminals has been previously reported in cases where the product achieves aromaticity [49][50][51], which is presumably the driving force for this transformation. Aminal 30

Amyloid-β probes: Review of structure–activity and brain-kinetics relationships

• Todd J. Eckroat,
• Abdelrahman S. Mayhoub and
• Sylvie Garneau-Tsodikova

Beilstein J. Org. Chem. 2013, 9, 1012–1044, doi:10.3762/bjoc.9.116

• amide 69, which was subsequently converted to the thioamide by using Lawesson’s reagent and cyclized to form the benzothiazole core 70 (Scheme 6B). Demethylation with BBr3 and protection of the resulting hydroxy moiety as the methoxymethyl (MOM) ether gave 71. Reduction of the nitro group to 72

• catalyzed Suzuki coupling of the starting halide 73 and boronic acid 74 followed by N-methylation of 75 with [3H]methyl iodide and O-demethylation with sodium thiophenoxide (Scheme 6C). Compound 57 showed high affinity for Aβ1-40 fibrils in vitro (Kd = 8.4 nM) and lower background binding levels than 56c

• installation of a trifluoroacetamide and O-demethylation gave the intermediate 118 used in a Mitsunobu reaction with 2-hydroxyethyl tosylate (119). Amine deprotection to 120 and installation of the [18F] label gave the target compound 98. Both 97 and 98 showed good affinity for Aβ1-42 aggregates (Ki = 4.5 nM

Aqueous reductive amination using a dendritic metal catalyst in a dialysis bag

• Jorgen S. Willemsen,
• Jan C. M. van Hest and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2013, 9, 960–965, doi:10.3762/bjoc.9.110

• ). The first step involved demethylation of 4,4’-dimethoxy-2,2’-bipyridine (1) in 92% yield [31]. Monofunctionalization of the ligand will lead to the highest possible catalyst loading per dendrimer and also prevents cross-linking between dendrimers. Therefore, a 1:1 mixture of isopropyl mesylate (5) and

Isotopically labeled sulfur compounds and synthetic selenium and tellurium analogues to study sulfur metabolism in marine bacteria

• Nelson L. Brock,
• Christian A. Citron,
• Claudia Zell,
• Martine Berger,
• Irene Wagner-Döbler,
• Jörn Petersen,
• Thorsten Brinkhoff,
• Meinhard Simon and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 942–950, doi:10.3762/bjoc.9.108

• incorporation of a deuterium label into MeSH and DMS. Knockout of relevant genes from the known DMSP demethylation pathway to MeSH showed in both species a residual production of [2H3]MeSH, suggesting that a second demethylation pathway is active. The role of DMSP degradation pathways for MeSH and DMS formation

• was further investigated by using the synthetic analogue DMTeP as a probe in feeding experiments with the wild-type strain and knockout mutants. Feeding of DMTeP to the R. pomeroyi knockout mutant resulted in a diminished, but not abolished production of demethylation pathway products. These results

• further corroborated the proposed second demethylation activity in R. pomeroyi. Isotopically labeled [2H3]methionine and 34SO42−, synthesized from elemental 34S8, were tested to identify alternative sulfur sources besides DMSP for the MeSH production in P. gallaeciensis. Methionine proved to be a viable

Preparation of mixed trialkyl alkylcarbonate derivatives of etidronic acid via an unusual route

• Petri A. Turhanen,
• Janne Weisell and
• Jouko J. Vepsäläinen

Beilstein J. Org. Chem. 2012, 8, 2019–2024, doi:10.3762/bjoc.8.228

• etidronate and alkyl chloroformate was developed by utilizing unexpected demethylation and decarboxylation reactions. The reaction with the sterically more hindered isobutyl chloroformate at a lower temperature (90 °C) produced the P,P'-diester (2) as a stable intermediate product. A possible reaction

• ). Conclusion Novel mixed trialkyl alkylcarbonate ester derivatives of HEBPA (3a–d) were prepared with good yields (65–76%) via an unusual demethylation, decarboxylation and 1,5-migration route. In addition a novel P,P'-diester alkylcarbonate derivative 2 was isolated at a reasonable 62% yield and the

Cyclization of ortho-hydroxycinnamates to coumarins under mild conditions: A nucleophilic organocatalysis approach

• Florian Boeck,
• Max Blazejak,
• Markus R. Anneser and
• Lukas Hintermann

Beilstein J. Org. Chem. 2012, 8, 1630–1636, doi:10.3762/bjoc.8.186

• isomerization/cyclization [17]. (c) Lewis acid induced demethylation/cyclization [18]. Hypothetical catalytic cycle: Nucleophile-assisted cyclization of (E)-ethyl 2’-hydroxycinnamate (1) to coumarin (2). Proposed catalytic cycle, based on 31P NMR spectroscopic and color evidence. Screening of catalysts for

Synthesis of conformationally restricted glutamate and glutamine derivatives from carbonylation of orthopalladated phenylglycine derivatives

• Esteban P. Urriolabeitia,
• Eduardo Laga and
• Carlos Cativiela

Beilstein J. Org. Chem. 2012, 8, 1569–1575, doi:10.3762/bjoc.8.179

• . This is mainly due to the fact that the demethylation of the NMe2 unit shown in Scheme 4 is not a very favourable process, and the reaction can take a different outcome, especially if alternative pathways are accessible. Taking into account these facts, we can propose a sensible explanation for the

• different reactivity. Therefore, the attack of the oxygen of an O-bonded alcohol on the electrophilic acyl carbon in our complexes seems to be favoured, since no demethylation is involved, and the C–O coupling occurs selectively instead of the intramolecular C–N bond formation. It seems that the reaction is

• driven by the pathway that tends to avoid the demethylation, while the comparison of the different nucleophilic abilities of the species coordinated to the metal (O-bonded alcohols versus N-bonded amines) plays in this case only a minor role. Using the same arguments we can explain the different

Synthesis and characterization of Sant-75 derivatives as Hedgehog-pathway inhibitors

• Chao Che,
• Song Li,
• Bo Yang,
• Shengchang Xin,
• Zhixiong Yu,
• Taofeng Shao,
• Chuanye Tao,
• Shuo Lin and
• Zhen Yang

Beilstein J. Org. Chem. 2012, 8, 841–849, doi:10.3762/bjoc.8.94

• -substituted precursor 7c by the reduction of the nitro group to an amino group using an FeCl3–Zn system [41]. Subsequently, capping the amino group with a sulfonyl or acetyl group led to 7n and 7o, respectively. In regard to hydroxy or acid modification, the demethylation or hydrolysis released the

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols

• Marcin Jasiński,
• Dieter Lentz and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2012, 8, 662–674, doi:10.3762/bjoc.8.74

• yield (75%) by using ion-exchange resin DOWEX-50 at 50 °C (Table 2, entry 4). As shown for compound 8, simultaneous cleavage was also possible, and the analytically pure compound 14 was isolated in comparable yield (Table 2, entry 3). Alternatively, demethylation of 12 by treatment with boron tribromide

Synthesis of 5-(2-methoxy-1-naphthyl)- and 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene as 2,2'-disubstituted 1,1'-binaphthyls via benzannulated enyne–allenes

• Yu-Hsuan Wang,
• Joshua F. Bailey,
• Jeffrey L. Petersen and
• Kung K. Wang

Beilstein J. Org. Chem. 2011, 7, 496–502, doi:10.3762/bjoc.7.58

• )-11H-benzo[b]fluorene 20a and 20b. Synthesis of 5-[2-(methoxymethyl)-1-naphthyl]-11H-benzo[b]fluorene 20c. Demethylation of 22b to form 5-(2-hydroxy-1-naphthyl)-11H-benzo[b]fluorene 24. Supporting Information Supporting Information File 142: Experimental procedures, spectroscopic data, and 1H and/or

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

An expedient synthesis of 5-n-alkylresorcinols and novel 5-n-alkylresorcinol haptens

• Kirsti Parikka and
• Kristiina Wähälä

Beilstein J. Org. Chem. 2009, 5, No. 22, doi:10.3762/bjoc.5.22

• reduced AR, the lack of stereochemical control was of no consequence. Following the Wittig reaction, catalytic hydrogenation and demethylation gave AR and AR haptens in ca. 40% overall yield. The Wittig product 7b was a practical starting material for the C23 hapten (2d), for which commercial alkanal or

Diels- Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

• Natsuno Etomi,
• Takuya Kumamoto,
• Waka Nakanishi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2008, 4, No. 15, doi:10.3762/bjoc.4.15

• indanetrione 8, but attempts with bromoindanone 18 resulted in no reaction even under reflux. Utilization of a milder oxidant phenyliodosyl bis(trifluoroacetate) (PIFA) [33] for the oxidation of phenolic indanone 20, derived from 18 by selective demethylation with magnesium iodide (MgI2) [34], gave

Colchitaxel, a coupled compound made from microtubule inhibitors colchicine and paclitaxel

• Karunananda Bombuwala,
• Thomas Kinstle,
• Vladimir Popik,
• Sonal O. Uppal,
• James B. Olesen,
• Jose Viña and
• Carol A. Heckman

Beilstein J. Org. Chem. 2006, 2, No. 13, doi:10.1186/1860-5397-2-13

• , is essential for microtubule binding activity, as change of the keto group to a thioketo group or demethylation of the OMe group in this ring reduced the activity [31](reviewed in [2]). Demethylation of the OMe group in ring A also decreased the activity, indicating the importance of this ring for