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