Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• fluorescence quantum yields were determined by using quinine sulfate dihydrate in sulfuric acid (0.5 N) as a standard at λexc = 325 nm (ΦF = 0.546) and coumarin 540A in ethanol as a standard at λexc = 450 nm (ΦF = 0.544). Photochromic reactions were induced in situ by a continuous irradiation Hg–Xe lamp

Carbohydrate PEGylation, an approach to improve pharmacological potency

• M. Eugenia Giorgi,
• Rosalía Agusti and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2014, 10, 1433–1444, doi:10.3762/bjoc.10.147

• with activated hydrophilic PEG to enhance its stability (Figure 5) [61]. Bifunctional PEGs were used to introduce a bioactive molecule, for instance biotine, coumarin, cholesterol or mannose into the distal end of a PEG-chitosan complex (Figure 6) [62]. Fructans have been PEGylated by reaction of

Rapid pseudo five-component synthesis of intensively blue luminescent 2,5-di(hetero)arylfurans via a Sonogashira–Glaser cyclization sequence

• Fabian Klukas,
• Alexander Grunwald,
• Franziska Menschel and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 672–679, doi:10.3762/bjoc.10.60

• recorded in dichloromethane and the fluorescence quantum yields Φf were determined with coumarin 1 or p-terphenyl as references (Table 2). The most furans display intense, broad absorption bands between 321 and 358 nm with molar extinction coefficients between 21000 to 35000 L/mol cm−1. In addition

The myxocoumarins A and B from Stigmatella aurantiaca strain MYX-030

• Tobias A. M. Gulder,
• Snežana Neff,
• Traugott Schüz,
• Tammo Winkler,
• René Gees and
• Bettina Böhlendorf

Beilstein J. Org. Chem. 2013, 9, 2579–2585, doi:10.3762/bjoc.9.293

• . This observation thus firmly validated that the methyl ether had to be situated at C-5, as its alternative location at C-7 would have led to a strong increase in signal intensity of the protons bound to both, C-6 and C-7. Owing to its coumarin core structure and its biological origin, compound 7 was

• of existing coumarin structures in literature, the 5-hydroxy-7-nitro substitution pattern combined with the unusual long-chain, fully saturated alkyl substituent at C-4 are unique to the myxcoumarins 7 and 9. With the production of myxothiazol A (5) and aurachin A (6), the investigated strain

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• aromatic guests under controlled, homogenous reaction conditions. The quantum yields for unsubstituted anthracene, acenaphthylene, and coumarin complexed in these γ-CD thioethers were found to be up to 10 times higher than in the non-complexed state. The configuration of the photoproduct reflected the

• configuration of the dimeric inclusion complex of the guest. Anti-parallel orientation of acenaphthylene within the CD cavity led to the exclusive formation of the anti photo-dimer in quantitative yield. Parallel orientation of coumarin within the complex of a CD thioether led to the formation of the syn head

• -to-head dimer. The degree of complexation of coumarin could be increased by employing the salting out effect. Keywords: acenaphthylene; anthracene; coumarin; cyclodextrins; photodimerization; quantum yield; stereoselectivity; Introduction Photochemical reactions have been considered highly

Raman spectroscopy as a tool for monitoring mesoscale continuous-flow organic synthesis: Equipment interface and assessment in four medicinally-relevant reactions

• Trevor A. Hamlin and
• Nicholas E. Leadbeater

Beilstein J. Org. Chem. 2013, 9, 1843–1852, doi:10.3762/bjoc.9.215

• determine whether we could observe spectroscopically a slug of the coumarin passing through the flow cell. The Raman spectrum of 1 (Figure 2) exhibits strong Raman-active stretching modes at 1608 cm−1 and 1563 cm−1 while the salicylaldehyde and ethyl acetoacetate starting materials exhibit minimal Raman

• s in an automated fashion as the coumarin passed through the cell by using the “continuous-scan” function on our spectrometer. By subtracting the spectrum of the solvent mixture (1:1 ethyl acetate:acetone) from the spectra recorded, we were able to clearly see the growth of the signal due to 1

• signals from the starting salicylaldehyde (9.84 ppm) and the coumarin product (8.45 ppm) [36]. Obtaining a relationship between signal strength and concentration: To obtain a calibration curve, spectra of 3-acetylcoumarin in 1:1 ethyl acetate/acetone were recorded at a range of concentrations by passing

Synthesis and spectroscopic properties of 4-amino-1,8-naphthalimide derivatives involving the carboxylic group: a new molecular probe for ZnO nanoparticles with unusual fluorescence features

• Laura Bekere,
• David Gachet,
• Vladimir Lokshin,
• Wladimir Marine and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2013, 9, 1311–1318, doi:10.3762/bjoc.9.147

• recorded using 1 cm quartz cells. The quantum yield of fluorescence was determined by using coumarin 153 as a reference in toluene and ethanol at 20 °C. Fluorescence lifetime measurements were performed by using time-correlated single photon counting (TCSPC) spectroscopy. Femtosecond pulses (150 fs, 80 MHz

A new synthetic protocol for coumarin amino acid

• Xinyi Xu,
• Xiaosong Hu and
• Jiangyun Wang

Beilstein J. Org. Chem. 2013, 9, 254–259, doi:10.3762/bjoc.9.30

• and relatively easy to prepare this kind of fluorescent amino acid with the new synthetic method. Furthermore, it can be applied to synthesize other derivatives of the coumarin amino acid with some specific properties. Keywords: coumarin; fluorescent probe; halogen derivatives; non-natural amino acid

• coumarin amino acid 1a (Figure 1) is sensitive to both pH and solvent polarity, which makes it a good probe to investigate protein functionalities and biological processes related to them. The following examples are several applications of it. Shan and co-workers used compound 1a to form a FRET pair with

• were then removed and racemic amino acid 1a was afforded. This approach prevents the tedious and costly HPLC purification step used in approach 1. However, it can only provide compound 1a as a racemic mixture, and some reagents used are not readily available. Due to the great importance of coumarin

Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

• Maddi Sridhar Reddy,
• Nuligonda Thirupathi and
• Madala Haribabu

Beilstein J. Org. Chem. 2013, 9, 180–184, doi:10.3762/bjoc.9.21

• moderate yields. Keywords: A3 coupling; cooperative catalysis; coumarin synthesis; cycloisomerization; transition-metal catalysts; Introduction An alkyne, an aldehyde and an amine coupling, referred to as A3 coupling [1], has been found as an efficient method for C–N and C–C bond formation that results

Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions

• Matthias Leven,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18

• mixture was subjected to column chromatography without quenching, and all yields were determined as isolated yields. The ee’s were established by chiral HPLC according to racemic standards and literature data [23]. 4-Hydroxy-3-(3-oxo-1-phenylbutyl)coumarin (warfarin). 1H and 13C NMR data were found to be

• )coumarin. 1H and 13C NMR data were found to be in agreement with the literature data [23]. Chiral HPLC: The measurements were performed with an eluent consisting of 80% hexanes and 20% isopropanol on a Diacel Chiralpak AD-H column with 0.8 mL/min flow. The detector wavelength was 254 nm. tR = 12.0 min

• (minor, (S)-enantiomer) and 13.3 min (major, (R)-enantiomer [23]. 4-Hydroxy-3-(3-oxocycloheptyl)coumarin. 1H and 13C NMR data were found to be in agreement with the literature data [23]. Chiral HPLC: The measurements were performed with an eluent consisting of 90% hexanes and 10% isopropanol on a Diacel

Thioester derivatives of the natural product psammaplin A as potent histone deacetylase inhibitors

• Matthias G. J. Baud,
• Thomas Leiser,
• Vanessa Petrucci,
• Mekala Gunaratnam,
• Stephen Neidle,
• Franz-Josef Meyer-Almes and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2013, 9, 81–88, doi:10.3762/bjoc.9.11

• could potentially be responsible for thioester hydrolysis. We prepared and used synthetic probe 10 [30] (Scheme 3) in order to test this hypothesis. Coumarin-based probe 10 is known to react extremely fast with thiols through a Michael addition reaction. While the fluorescence of 10 is efficiently

A chemist and biologist talk to each other about caged neurotransmitters

• Graham C.R. Ellis-Davies

Beilstein J. Org. Chem. 2013, 9, 64–73, doi:10.3762/bjoc.9.8

• expense of another property, such as the rate of release [7]. For example, GABA caged directly as an ester with coumarin chromophores is photoreleased quickly, but is quite unstable in (frozen) solution [60]. However, when caged via a carbamate, its release is orders of magnitude slower, but the compounds

Reactions of salicylaldehyde and enolates or their equivalents: versatile synthetic routes to chromane derivatives

• Ishmael B. Masesane and
• Zelalem Yibralign Desta

Beilstein J. Org. Chem. 2012, 8, 2166–2175, doi:10.3762/bjoc.8.244

• ) with tert-butyl acrylate (56) to give the Baylis–Hillman product 57, which was subsequently cyclized in the presence of acetic acid to give chromene 58 in a low yield of 24%, together with coumarin 59 in 40% yield (Scheme 20). An asymmetric amine-catalyzed reaction of salicylaldehyde (5) and α,β

• of 2,2-dimethylchromene 45. Synthesis of 2,3-disubstituted chromene 47 by Stukan and co-workers. Ravichandrans synthesis of 3-substituted chromenes 52–55. Synthesis of 3-substituted chromene 58 coumarin 59 by Paye and co-workers. Govender and co-workers asymmetric synthesis of 2-phenylchromenes 62

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

• elimination to coumarin (2) could be driven by aromatic stabilization (Scheme 2). In fact, a related stoichiometric two-step protocol has been proposed [36]. It appeared to us that the practical problem of developing a mild and convenient catalytic conversion of ortho-hydroxycinnamates to the corresponding

• coumarins could be an ideal test case to show the utility of using organocatalytic rationales for solving a synthetic problem. Results and Discussion The reaction of (E)-ethyl 2’-hydroxycinnamate (1) to coumarin (2) was chosen as the assay to find catalytic activity under mild conditions (Table 1). It was

• initially thought that hydro-heteroatomic nucleophiles such as thiols, which are known to easily undergo hetero-Michael additions [38], could be suitable candidates for the screen. However, coumarin was not formed in the presence of thiols (Table 1, entry 1). We turned our attention to nucleophiles that are

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

• Kalicharan Chattopadhyay,
• Erik Fenster,
• Alexander J. Grenning and
• Jon A. Tunge

Beilstein J. Org. Chem. 2012, 8, 1200–1207, doi:10.3762/bjoc.8.133

• the biologically active coumarin motif. This new method was utilized to prepare a 128-membered library of aminated coumarins for biological screening. Keywords: benzylation; catalysis; coumarin; chemical diversity; decarboxylative; palladium; substitution; Introduction Coumarins are privileged

• ]. Due to the ambiphilic nature of the heterocyclic ring of coumarin, this core-structure undergoes a diverse array of coupling reactions, such as halogenations [25], cycloadditions [26][27][28][29][30][31][32], conjugate additions [33][34][35][36][37] and transition-metal-catalyzed C–H activation

• ketone enolates to the exo-methyl position of the coumarin core by this method (Table 1). Screening of reaction conditions showed that, in contrast to common decarboxylative benzylation conditions (Table 1,entries 1 and 2) under which nonpolar solvents give the best DcB, the selective mono-alkylation of

Asymmetric total synthesis of smyrindiol employing an organocatalytic aldol key step

• Dieter Enders,
• Jeanne Fronert,
• Tom Bisschops and
• Florian Boeck

Beilstein J. Org. Chem. 2012, 8, 1112–1117, doi:10.3762/bjoc.8.123

• intramolecular aldol reaction as the key step, is described. Smyrindiol was synthesized from commercially available 2,4-dihydroxybenzaldehyde in 15 steps, with excellent stereoselectivity (de = 99%, ee = 99%). In the course of this total synthesis a new and mild coumarin assembly was developed. Keywords: aldol

• intramolecular aldol reaction of O-acetonyl-salicylaldehydes was described by our research group (Scheme 3) [10]. We envisaged that this 5-enolexo aldolization could be utilized to construct the 1,3-diol moiety of smyrindiol, if a coumarin derivative of the O-acetonyl-salicylaldehyde were to be used. The

• probably the result of unwanted intermolecular side reactions of the keto group of one molecule on the coumarin system of another molecule, as an NMR analysis of the reaction mixture showed that an aldehyde signal was still present after the reaction and had, thus, not taken part in the aldol reaction. For

Dioxane dibromide mediated bromination of substituted coumarins under solvent-free conditions

• Subrata Kumar Chaudhuri,
• Sanchita Roy and
• Sanjay Bhar

Beilstein J. Org. Chem. 2012, 8, 323–329, doi:10.3762/bjoc.8.35

• detailed results are summarized in Table 1. When an unsubstituted coumarin (1a) was subjected to bromination with DD under solvent-free conditions, vicinally anti-dibromide 2a was obtained exclusively through electrophilic addition of bromine across the electron-deficient double bond of the conjugated δ

• in 1e and 1f, vinylic bromination occurred regioselectively to furnish 2e and 2f in high yield without further bromination at C6 and C8, when a stoichiometric amount of DD was used (Table 1, entries 6 and 7). Interestingly, 7-(allyloxy)coumarin (1g) underwent chemoselective addition of bromine across

• 6.27 with J = 9.4 Hz and olefinic hydrogen at C4 appeared at δ 7.65 with J = 9.5 Hz, corresponding to the mutually cis-orientation of the two hydrogens across the C3–C4 olefinic linkage of the coumarin system. Three peaks in the ratio 1:2:1 as the molecular ion peaks in the mass spectrum also

Synthesis and characterization of new diiodocoumarin derivatives with promising antimicrobial activities

• Hany M. Mohamed,
• Ashraf H. F. Abd EL-Wahab,
• Ahmed M. EL-Agrody,
• Ahmed H. Bedair,
• Fathy A. Eid,
• Mostafa M. Khafagy and
• Kamal A. Abd-EL-Rehem

Beilstein J. Org. Chem. 2011, 7, 1688–1696, doi:10.3762/bjoc.7.199

• ]. Moreover, coumarin-based dyes and pigments are organic fluorescent materials exhibiting unique photochemical and photophysical properties, which render them useful in a variety of applications such as dye lasers, anion sensors, organic light-emitting diodes and solar cells [9][10]. Iodo-organic derivatives

• intensity): 460 (M+, 2.6), 459 (M – 1, 30.4), 425 (83.4), 341 (19.3), 214 (10.9), 87 (100). 6,8-Diiodo-3-(piperidine-1-carbonyl)coumarin (4). A solution of compound 1 (0.47 g, 10 mmol) in absolute ethanol (30 mL) was refluxed with piperidine (0.9 g, 10 mmol) for 1 h. After cooling, the solid formed was

Cationic gold(I) axially chiral biaryl bisphosphine complex-catalyzed atropselective synthesis of heterobiaryls

• Tetsuro Shibuya,
• Kyosuke Nakamura and
• Ken Tanaka

Beilstein J. Org. Chem. 2011, 7, 944–950, doi:10.3762/bjoc.7.105

• corresponding quinolinone and coumarin derivatives 2d–g in high yields with perfect regioselectivity, while the observed ee values were very low (<10% ee). However, interestingly, the use of (R)-BINAP as a ligand improved the enantoselectivity (14–32% ee, Table 2, entries 4–7). In the previously reported

Synthesis of the fluorescent amino acid rac-(7-hydroxycoumarin-4-yl)ethylglycine

• Manfred Braun and
• Torsten Dittrich

Beilstein J. Org. Chem. 2010, 6, No. 69, doi:10.3762/bjoc.6.69

• proteins, has been synthesized in five steps from commercially available (7-hydroxycoumarin-4-yl)acetic acid. The key step involves the alkylation of a glycine–enolate equivalent. Keywords: alkylation; coumarin; fluorescent probe; glycine; protecting group; Introduction The incorporation of non-natural

• selective protection of the phenolic hydroxyl group, the tert-butyl(dimethyl)silyl group [14] was chosen. Thus, coumarin 3 was treated with one equivalent of sodium hydride to generate the phenolate by selective deprotonation without abstraction of the proton from the primary alcohol moiety. Subsequent

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• substituent will influence the binding. The co-ordination of primary ammonium ions salts with varying steric demand was investigated. The sensing ability of fluorescently labelled 1,10-diaza-18-crown-6 (16) was compared to the analogous monoaza-18-crown-6 coumarin sensor (15) [130]. The co-ordination

Synthetic incorporation of Nile Blue into DNA using 2′-deoxyriboside substitutes: Representative comparison of (R)- and (S)-aminopropanediol as an acyclic linker

• Daniel Lachmann,
• Sina Berndl,
• Otto S. Wolfbeis and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2010, 6, No. 13, doi:10.3762/bjoc.6.13

• basic conditions of automated DNA phosphoramidite chemistry and/or DNA workup. We recently presented the postsynthetic incorporation of Nile Blue and a coumarin dye as representatives of base-labile fluorophores by the “click” ligation strategy [17]. Several other fluorophores (spanning the whole

Novel base catalysed rearrangement of sultone oximes to 1,2-benzisoxazole- 3-methane sulfonate derivatives

• Veera Reddy Arava,
• Udaya Bhaskara Rao Siripalli,
• Vaishali Nadkarni and
• Rajendiran Chinnapillai

Beilstein J. Org. Chem. 2007, 3, No. 20, doi:10.1186/1860-5397-3-20

• was developed by Dianippon of Japan. Compounds 1 were originally prepared from the rearrangement of coumarin-4-one oximes 3 as shown in Scheme 1. The 1,2-benzisoxazole-3-acetic acids were converted into halogenated compounds, then reacted with various different nucleophiles to generate the compounds 1

• Supporting Information File 1 for full experimental data. Conversion of coumarin-4-one oximes to 3-alkyl-1,2-benzisoxazole derivatives. Reactions of 3-halomethyl derivatives with other nucleophiles. Sultone oximes and its precursor ketones. Synthesis of 1,2-benzoxathiin-4(3H)-one-2,2-dioxide 6 from

Synthesis of coumarin or ferrocene labeled nucleosides via Staudinger ligation

• Ivana Kosiova,
• Andrea Janicova and
• Pavol Kois

Beilstein J. Org. Chem. 2006, 2, No. 23, doi:10.1186/1860-5397-2-23

• nucleic acids. Results A new approach for the preparation of labeled nucleosides via intermolecular Staudinger ligation is described. Reaction of azidonucleosides with triphenylphosphine lead to iminophosphorane intermediates, which react subsequently with derivatives of coumarin or ferrocene to form

• coumarin or ferrocene labeled nucleosides. Fluorescent properties of coumarin labeled nucleosides are determined. Conclusion New coumarin and ferrocene labeled nucleosides were prepared via intermolecular Staudinger ligation. This reaction joins the fluorescent coumarin and biospecific nucleoside to the

• , [22][23] including specific labeling of nucleic acids, [24] proteomic studies [25][26] and modification of cell surfaces. [17][18] We applied the Staudinger ligation for nucleoside labeling procedures, using coumarin and ferrocene derivatives as labels. According to our knowledge, applications of this