A novel high-yield synthesis of aminoacyl p-nitroanilines and aminoacyl 7-amino-4-methylcoumarins: Important synthons for the synthesis of chromogenic/fluorogenic protease substrates

• Xinghua Wu,
• Yu Chen,
• Herve Aloysius and
• Longqin Hu

Beilstein J. Org. Chem. 2011, 7, 1030–1035, doi:10.3762/bjoc.7.117

• acid/peptide conjugates liberates the free chromophore or fluorophore, allowing the convenient determination of the rate of enzyme catalysis with a UV or fluorescence spectrophotometer. p-Nitroaniline (pNA) is one of the most commonly used chromogenic reagents. The synthesis of peptide-pNAs usually

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• transformation does not require H-atom abstraction from an external H-atom source such as CHD and DNA, and thus the DNA-damaging ability of this chromophore is not expected to be significant. Photophysics and kinetics of photoinduced electron transfer The fluorescence quenching by triethylamine (Et3N) was

• . A similar trend has been previously observed for the lifetimes of m-substituted enediynes [63]. The absorption spectra of all four acetylenes are shown in Figure 6. The core Ph-TFP-acetylene (Ph-TFP) chromophore without the amide group has no significant absorption at >320 nm. The lowest absorptions

• hydroxyl radical scavengers, glycerol and DMSO, protected DNA from the cleavage by 33 and 26%, respectively, whereas NaN3 showed ~43% protection. The large protecting effect of NaN3, the singlet oxygen scavenger, is consistent with the efficient photoaddition reaction of its chromophore via triplet

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• is due to the optical transition attributed to the presence of the auxochromic OH group, which increases the conjugation length [31] and becomes part of extended chromophore. This effect is absent in the other compounds. The photoluminescence spectra of the polymer solutions of series P1 and P2 in

Stereogenic boron in 2-amino-1,1-diphenylethanol-based boronate–imine and amine complexes

• Sebastian Schlecht,
• Walter Frank and
• Manfred Braun

Beilstein J. Org. Chem. 2011, 7, 615–621, doi:10.3762/bjoc.7.72

• = 395 nm, typical for the imine chromophore, as observed for other boronate–imine complexes. The imine 7 also served for the preparation of the boronate–amine complex 10. For this purpose, it was reduced [22] with cyanoborohydride in methanol in the presence of hydrochloric acid to give the salt of the

• 10 in 63% isolated yield. The lack of any absorption at wavelengths higher than 350 nm indicated the absence of the imine chromophore. Here again the formation of the complex can be deduced from the 11B NMR shift of 5.5 ppm [21]. Suitable crystals of compound 10·CH3OH were obtained from methanol

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• enthalpy of the radical ion pair formation, ΔEexcit = excitation energy of the chromophore, ΔEcoul = coulomb interaction energy of the radical ions and = half wave potential of donor and acceptor. If electron transfer pathways dominate, substitution reactions are found to prevail. However, if the electron

Photoinduced electron-transfer chemistry of the bielectrophoric N-phthaloyl derivatives of the amino acids tyrosine, histidine and tryptophan

• Axel G. Griesbeck,
• Jörg Neudörfl and
• Alan de Kiff

Beilstein J. Org. Chem. 2011, 7, 518–524, doi:10.3762/bjoc.7.60

• +, electronically excited phthalimides are potent electron acceptors [2]. The rich photochemistry of this chromophore has recently been reviewed [3][4]. Intramolecular hydrogen abstraction is an archetype process for electronically excited carbonyl groups (Norrish type II reaction). The 1,4-biradicals formed by γ

Supramolecular FRET photocyclodimerization of anthracenecarboxylate with naphthalene-capped γ-cyclodextrin

• Qian Wang,
• Cheng Yang,
• Gaku Fukuhara,
• Tadashi Mori,
• Yu Liu and
• Yoshihisa Inoue

Beilstein J. Org. Chem. 2011, 7, 290–297, doi:10.3762/bjoc.7.38

• of 7, where the included naphthalene chromophores are arranged in a right-handed screw [24]. As can be seen from Figure 3, naphthalene-capped γ-CD 6 gave only weak induced circular dichroism signals at the 1La and 1Bb bands of the naphthalene chromophore, the intensity of which was not concentration

• examination revealed that the FRET from the excited naphthalene on CD rim to AC included in the CD cavity is operative upon excitation of the naphthalene chromophore at 296 nm. Circular dichroism spectral studies revealed that the two AC molecules are arranged in a right-handed screw sense in the CD cavity

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• auxiliary strategy was developed by Scheffer et al. which allows to influence the stereoselectivity of solid-state photoreactions by chiral counter ions [34]. This is accomplished by providing the chromophore under investigation with a carboxylic acid functionality and then by attaching a chiral

• latter in solution. For that purpose the dibenzobarrelene chromophore was functionalized with ureido or thioureido substituents, since these functionalities are strong hydrogen bonding donors, which may associate with (chiral) anions [38][39]. Moreover, the versatile use of urea and thiourea derivatives

• the dibenzobarrelene unit, by comparison with the absorption of the resembling dibenzobarrelene derivative 1d [45]. This observation indicates that the complexation of the chloride anion has no significant influence on the dibenzobarrelene chromophore, but rather on the trifluoromethyl-substituted

Synthesis of cationic dibenzosemibullvalene-based phase-transfer catalysts by di-π-methane rearrangements of pyrrolinium-annelated dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 119–126, doi:10.3762/bjoc.7.17

• separated. Since the covalent attachment of a sensitizer unit to the dibenzobarrelene chromophore did not induce the desired triplet sensitization, the ionic auxiliary strategy [19] was applied to achieve triplet-sensitization in the solid-state, i.e., the sensitizer was introduced as counter anion. For

An easy assembled fluorescent sensor for dicarboxylates and acidic amino acids

• Xiao-bo Zhou,
• Yuk-Wang Yip,
• Wing-Hong Chan and
• Albert W. M. Lee

Beilstein J. Org. Chem. 2011, 7, 75–81, doi:10.3762/bjoc.7.11

• (i.e., chromophore or fluorophore) as sensing probes for dicarboxylates [8][9][10][11][12][13]. Additionally, chiral recognition of carboxylates has been actively explored in the sensor field [14][15][16]. By using cholic acid as the molecular scaffold for the construction of sensing probes, we have

Self-assembly and semiconductivity of an oligothiophene supergelator

• Pampa Pratihar,
• Suhrit Ghosh,
• Vladimir Stepanenko,
• Sameer Patwardhan,
• Ferdinand C. Grozema,
• Laurens D. A. Siebbeles and
• Frank Würthner

Beilstein J. Org. Chem. 2010, 6, 1070–1078, doi:10.3762/bjoc.6.122

• spectroscopy Self-assembly of T1 in solution was examined by UV-vis spectroscopy. Chloroform is known to be an excellent solvent for the study of rigid π-systems [20][21], and the oligothiophene chromophore T1 has good solubility in this solvent. However, as noted above, in nonpolar solvents such as n-heptane

Donor-acceptor substituted phenylethynyltriphenylenes – excited state intramolecular charge transfer, solvatochromic absorption and fluorescence emission

• Ritesh Nandy and
• Sethuraman Sankararaman

Beilstein J. Org. Chem. 2010, 6, 992–1001, doi:10.3762/bjoc.6.112

• . These results indicate that the fluorescence emission arises from excited state intramolecular charge transfer in these molecules where the triphenylene chromophore acts either as a donor or as an acceptor depending upon the nature of the substituent on the phenyl ring. HOMO–LUMO energy gaps have been

• and also by substituting donor-acceptor groups along the conjugation [23][24][25]. In addition, pyrene also exhibits excimer emission at a longer wavelength compared to monomer emission which can be used in sensing applications [26][27][28][29][30]. The pyrene chromophore can act as a donor or as an

• acceptor depending upon the substituent. Pyrene- π spacer-donor and pyrene- π spacer-acceptor type molecules have been widely studied and they have been used in sensing, photo and electro-luminescence applications [31][32][33][34][35][36]. Unlike pyrene, the triphenylene chromophore has not been widely

Conjugated polymers containing diketopyrrolopyrrole units in the main chain

• Bernd Tieke,
• A. Raman Rabindranath,
• Kai Zhang and
• Yu Zhu

Beilstein J. Org. Chem. 2010, 6, 830–845, doi:10.3762/bjoc.6.92

• fastness, deep colour, luminescence with large Stokes-shifts, and a brilliant red colour enabling technical applications in colouring of fibers, plastics and surface coatings such as prints or inks. The electron-withdrawing effect of the lactam units causes the chromophore to have a high electron affinity

• . Strong hydrogen bonding between the lactam units favors the chromophores forming physically cross-linked chain structures in the solid state, which is the origin for the poor solubility [7][8]. Short distances between the chromophore planes (0.336 nm) and phenyl ring planes (0.354 nm) enable π-π

• , and the chromophore requires to be functionalized with polymerizable groups. The solubility can be increased by N-alkylation [10], arylation [11] or acylation [12] of the lactam units thus preventing hydrogen bond formation between the chromophores. Polymerizable groups can be attached to the aryl

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

• polymers [2][3][4]. In general, there are two approaches for the synthesis of fluorescent polymers: First, the polymerization of a monomer that contains a fluorescent chromophore is possible. However, in some cases the new fluorophore-carrying polymer [1][5] is accompanied by a non-adequate effort

• heterocycle 8-oxo-8H-acenaphtho[1,2-b]pyrrol-9-carbonitrile (1) is a type of novel fluorescent chromophore with long-wavelength absorption and fluorescence, the excitation and emission wavelengths of which can reach 530 nm and 590 nm, respectively [36]. It is well known, that carbonitrile 1 is able to react

• with the thiolated RGD peptide cyclo(Arg-Gly_Asp-Phe-Lys(mpa))(c(RGDFK)-SH) leads to a fluorescent sensor for imaging tumor cells [37]. In this paper we report our current studies on the functionalization of PVAm with carbonitrile 1 to introduce a chromophore as well as a fluorophore into the polymer

RAFT polymers for protein recognition

• Alan F. Tominey,
• Julia Liese,
• Sun Wei,
• Klaus Kowski,
• Thomas Schrader and
• Arno Kraft

Beilstein J. Org. Chem. 2010, 6, No. 66, doi:10.3762/bjoc.6.66

• produced slightly higher polydispersities (1.56). For comparison, some copolymers such as S20CH15 were also prepared with a molecular weight of ~3000 g mol−1. Titrations were first carried out by UV–vis spectroscopy with cytochrome C, a protein carrying a chromophore. Second derivative spectra were

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

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

• Nile Blue chromophore was incorporated into oligonucleotides using “click” chemistry for the postsynthetic modification of oligonucleotides. These were synthesized using DNA building block 3 bearing an alkyne group and reacted with the azide 4. (R)-3-amino-1,2-propanediol was applied as the linker

• between the phosphodiester bridges. Two sets of DNA duplexes were prepared. One set carried the chromophore in an A-T environment, the second set in a G-C environment. Both were characterized by optical spectroscopy. Sequence-dependent fluorescence quenching was applied as a sensitive tool to compare the

• the chromophore to intercalate. The major difference between the 3-amino-1,2-propanediol linker and the 2′-deoxyribofuranoside is the number of carbon atoms between the phosphodiester bridges in the corresponding modified oligonucleotides which has been reduced from 3 (in normal nucleosides) to 2

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• to, or deprotonation/protonation of, the indolocarbazole moiety might modulate the electronic properties of chromophore [46] and give rise to significant color changes. The interaction of receptor 1 (c = 1.1 × 10−4 M) with F− was investigated in aqueous CH3CN solvent in more detail by UV–vis

An enantiomerically pure siderophore type ligand for the diastereoselective 1 : 1 complexation of lanthanide(III) ions

• Markus Albrecht,
• Olga Osetska,
• Thomas Abel,
• Gebhard Haberhauer and
• Eva Ziegler

Beilstein J. Org. Chem. 2009, 5, No. 78, doi:10.3762/bjoc.5.78

• exhibits Λ2 conformation in solution, too. The positive Cotton effect at 295 nm as well as the negative Cotton effect at 280 nm are found in both spectra. These effects derive from an exciton coupling [38] of the 8-hydroxyquinoline chromophore and therefore they can be used for the unambiguous

Synthesis of rigidified flavin–guanidinium ion conjugates and investigation of their photocatalytic properties

• Harald Schmaderer,
• Mouchumi Bhuyan and
• Burkhard König

Beilstein J. Org. Chem. 2009, 5, No. 26, doi:10.3762/bjoc.5.26

• catalytic efficacy, flavin derivatives bearing a guanidinium ion as oxoanion binding site were prepared. Chromophore and substrate binding site are linked by a rigid Kemp’s acid structure. The molecular structure of the new flavins was confirmed by an X-ray structure analysis and their photocatalytic

• ][25][26][27][28][29][30]. A general drawback of photochemical processes in homogeneous solution is the limited preorganization of the reactants and the chromophore, which may lead to low selectivities and slow conversions in diffusion controlled reactions. To overcome this problem, Kemp’s acid [31

• flavin chromophore, the guanidinium substrate binding site and a Kemp’s acid derived rigid linker, starts from Kemp’s acid anhydride (5) [50][51][52]. The anhydride 5 was allowed to react with previously prepared flavins 4 and 8 [21] in the presence of DMAP as catalyst. The amide formation of the

Convenient methods for preparing π-conjugated linkers as building blocks for modular chemistry

• Jiří Kulhánek,
• Filip Bureš and
• Miroslav Ludwig

Beilstein J. Org. Chem. 2009, 5, No. 11, doi:10.3762/bjoc.5.11

• ], organic light-emitting diodes (OLED) [9] or functional polymers [10][11][12][13]. A typical push-pull chromophore consists of a polar A-π-D system with a planar π-system end-capped by a strong electron donor (D) and a strong electron acceptor (A). The π-conjugated system ensuring charge-transfer (CT

• the extension or shortening of the π-conjugated path between the donor and acceptor [19][21][23][24][25]. Thus, the latter modular synthetic approach seems to be more suitable for the property tuning described above. The final combination, C–C bond formation, of the donor and acceptor chromophore