Studying specificity in protein–glycosaminoglycan recognition with umbrella sampling

• Mateusz Marcisz,
• Sebastian Anila,
• Margrethe Gaardløs,
• Martin Zacharias and
• Sergey A. Samsonov

Beilstein J. Org. Chem. 2023, 19, 1933–1946, doi:10.3762/bjoc.19.144

• essential to explain their biological functions. In this study, the umbrella sampling (US) approach is used to pull away a GAG ligand from the binding site and then pull it back in. We analyze the binding interactions between GAGs of three types (heparin, desulfated heparan sulfate, and chondroitin sulfate

• /pdb, [37]). The third complex is known to exist in two different binding poses which are experimentally well established. In this study, the umbrella sampling (US) approach is used to pull away a GAG ligand from the binding site and then pull it back in. The main focus of our study is to evaluate

• ligand from its bound position and allowing the ligand to approach the protein from a very distant position to the binding sites. Materials and Methods Structures and parameters Ligand preparation GAG structures used in the study consist of two parts: 1. the part from the experimental structure (heparin

N-Boc-α-diazo glutarimide as efficient reagent for assembling N-heterocycle-glutarimide diads via Rh(II)-catalyzed N–H insertion reaction

• Grigory Kantin,
• Pavel Golubev,
• Alexander Sapegin,
• Alexander Bunev and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 1841–1848, doi:10.3762/bjoc.19.136

• ][10], potentially opening a path for its use in treating KRAS-induced cancers. A common characteristic of the degraders elaborated in the literature involves the compulsory integration of an E3-ligase ligand motif into the PROTAC configuration [11]. The E3-ligase most frequently utilized in TPD

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• maintaining high selectivity for carbon products. Results and Discussion Synthesis and characterization of the new Co(II)-based catalyst The novel cobalt(II) complex 1 was synthesized in dry methanol (MeOH) by mixing in a 2:1 ratio, the chelating diimine ligand, 1-benzyl-4-(quinolin-2-yl)-1H-1,2,3-triazole

• chosen solvent for photocatalysis. The absorption profile evokes the structured band of the free ligand BzQuTr [42], with two intense π–π* ligand-centered transitions at circa 319 nm and 330 nm (Figure 3). The pink solid dissolves as an intense blue DMA solution. Nevertheless, the d–d transitions

• ), respectively. A more intense current arises with the third redox process occurring at −2.52 V, which could be assigned to the reduction localized on the ligand (compare with the cyclic voltammogram in Supporting Information File 1, Figure S8). We investigated the electrochemical properties also under a CO2

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• planar to an octahedral. The water molecule and the hydroxide anion occupied ligand positions on both sides of the median central-core plane, hydrogen bonding to the flexible crown ether part of 16 (Scheme 6). The intramolecular flexibility of compound 16 allowed for tightening/loosening of the cleft

• flexibility of macrocyclic ligands, as demonstrated by X-ray molecular structures. The helicates consisted of two metal centres, namely cobalt, manganese, or iron, each coordinated by two nitrogens and oxygen donors of the ligand. The metal centres adopted distorted octahedral geometries with slight

• deviations from the N3O plane. An intriguing feature of the helicates was their short metal–metal separation (3.151 Å [Fe], 3.521 Å [Mn], and 3.104 Å [Co]) enabled by the flexibility of the ligand incorporating the sp3-hybridised meso-carbons. Crownphyrins and similar systems In 2022 our group reported on

Cyclodextrins permeabilize DPPC liposome membranes: a focus on cholesterol content, cyclodextrin type, and concentration

• Ghenwa Nasr,
• Hélène Greige-Gerges,
• Sophie Fourmentin,
• Abdelhamid Elaissari and
• Nathalie Khreich

Beilstein J. Org. Chem. 2023, 19, 1570–1579, doi:10.3762/bjoc.19.115

• hydroxypropyl-β-CD (HPBCD, DS = 5.6) were provided by Roquette Frères (Lestrem, France). Sulfobutyl ether-β-CD (SBE-β-CD, DS = 6.5) was provided by LIGAND Pharmaceuticals (San Diego, CA, USA). Dipalmitoylphosphatidylcholine (DPPC) and trizma base (buffer reagent) were purchased from Sigma-Aldrich, Switzerland

C–H bond functionalization: recent discoveries and future directions

• Indranil Chatterjee

Beilstein J. Org. Chem. 2023, 19, 1568–1569, doi:10.3762/bjoc.19.114

• the abstraction of intramolecular hydrogen atoms. Radical chemistry is a viable alternative to the two-electron process, involving C–H bond functionalization in the absence of any ligand and using low-cost redox-active metals (Fe, Cu, Mn, etc.) rather than heavy metals (Rh, Ir, etc.). Although radical

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• intermediate III. Reductive elimination of Pd from III gave product 5 and species IV. Finaly, Pd(II) species were reproduced by ligand exchange to restart the next cycle (Scheme 4). In 2014, Fu and co-workers described a facile method for the C–H thiolation of phenols 7 with 1-(substituted phenylthio

• )pyrrolidine-2,5-diones 1 using FeCl3 or BF3·OEt2 as a catalyst (Scheme 5) [46]. A wide variety of thiolated phenols 8 were produced under mild reaction conditions without using any base, ligand, or additive. For both substrates, 7 and 1 aryl rings containing electron-donating groups exhibited a higher

• sulfide moieties 11 was performed by Fu et al. (Scheme 6) [47]. Iron(III) chloride was used as a catalyst for this coupling reaction without the need of any ligand and additive. Screening for other metal salts, such as Cu(OAc)2, Pd(OAc)2, AgOAc or CuI was not successful, although FeS·7H2O, FeS, Fe2(SO4)3

Application of N-heterocyclic carbene–Cu(I) complexes as catalysts in organic synthesis: a review

• Nosheen Beig,
• Varsha Goyal and
• Raj K. Bansal

Beilstein J. Org. Chem. 2023, 19, 1408–1442, doi:10.3762/bjoc.19.102

• copper(I) bromide in CH2Cl2 (Scheme 24) [31]. Nakamura et al. synthesized for the first time a copper complex with a 1,2,3-triazole carbene ligand in 2011. Complexes of copper with 1,4-diphenyl-, 1,4-dimesityl-, and 1-(2,6-diisopropylphenyl)-4-(3,5-xylyl)-1,2,3-triazol-5-ylidene were prepared through

• catalysts for hydrosilylation and [3 + 2] cycloaddition discussed later [39]. 1.4 By ligand displacement Corrigan and co-worker stabilized homoleptic copper- and silver bis(trimethylsilyl)phosphido compounds [M6{P(SiMe3)2}6] (M = Cu, Ag) through their coordination with NHC ligands. For this purpose, they

• the respective ligand with the copper salts in THF [43]. In the same year, Sanford and co-workers [44] synthesized the first isolable NHC–Cu(I)–difluoromethyl complexes 91 (Scheme 31). Owing to the low stability of [Cu(CHF2)] species, larger/bulky ligands like IPr, SiPr, etc. were used to obtain

One-pot nucleophilic substitution–double click reactions of biazides leading to functionalized bis(1,2,3-triazole) derivatives

• Hans-Ulrich Reissig and
• Fei Yu

Beilstein J. Org. Chem. 2023, 19, 1399–1407, doi:10.3762/bjoc.19.101

• (bromomethyl)benzene furnished geometrically differing bis(1,2,3-triazole) derivatives. The use of tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) as ligand for the click step turned out to be very advantageous. The compounds with 1,2-oxazinyl end groups can potentially serve as precursors of divalent

• presence of sodium ascorbate as reducing agent and sodium carbonate as base as well as ʟ-proline as ligand in a DMF/water mixture at 60 °C provided this promising result. These conditions applied are similar to those described by Fokin et al. [24], which had also been employed by other groups [37][38]. The

• we examined the influence of the ligand tris[(1-benzyl-1H-1,2,3-triazol-4-yl)methyl]amine (TBTA) which has been identified by Sharpless et al. [58] as a very beneficial component in CuAAC reactions. After comprehensive optimization, we found that the addition of 0.2 equiv of this ligand not only

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

•  1. Benzoguanidine has an extended π-conjugation compared with carbazole and is more nitrogen-rich (three N-atoms vs one in carbazole). Thompson et al. recently reported a series of carbene–metal–amide (CMA) (metal = Cu, Ag, Au) emitters employing a benzoguanidine ligand [10]. The extended π

• containing a rigid benzoguanidine ligand in its molecular structure. Results and Discussion Synthesis and structure 4BGIPN was prepared in 70% yield by aromatic nucleophilic substitution reaction from 2,4,5,6-tetrafluoroisophthalonitrile and 5H-benzo[d]benzo[4,5]imidazo[1,2-a]imidazole (benzoguanidine) after

• experiment from 1.402(5) to 1.420(5), giving an average of 1.407(13) Å for 4BGIPN, which is closely similar to 1.405(8) Å reported for the benchmark 4CZIPN compound. Unlike carbazole, the benzoguanidine ligand lacks C2 rotational symmetry, thus enabling the benzoguanidine ligands to project above and below

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• have broad applications in synthesis. In 2019, Cai et al. developed a regioselective ligand-promoted CDC reaction between unactivated C(sp3)–H/C(sp3)–H bonds (Scheme 18) [79]. Different types of C(sp3)–H bond substrates, including cycloalkanes, cyclic ethers, and toluene derivatives without any

• directing groups could be used as coupling partners. The ligand acts as an activator of the catalyst to promote the reaction, and the iron-bound anion plays a crucial role in catalysis. This reaction might occur via a radical pathway, with the iron catalyst playing a significant role in electron transfer

• with Fe2(CO)9 as a catalyst and N1,N1,N2,N2-tetramethylethane-1,2-diamine (TMEDA) as bidentate ligand. A gram-scale alkylation reaction showed that the new procedure has excellent potential for synthetic applications. The mechanism study shows that radicals are the starting point of the coupling

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• engagement of alkyl radicals remains challenging. Among these functionalization approaches, a bio-inspired mechanistic paradigm known as radical ligand transfer (RLT) has emerged as a particularly promising and versatile means of forming new bonds catalytically to alkyl radicals. This development has been

• amenable to all radical generation approaches/substrate classes nor can they form all desired bonds from alkyl radical intermediates, limiting the toolkit of radical reactions. Recently, radical ligand transfer (RLT) [9][10][11] has emerged as a radical functionalization paradigm with the potential to

• overcome the challenges faced by other strategies (Scheme 1). At its core, RLT involves the outer sphere transfer of an anionic, X-type ligand coordinated to a redox-active metal to a radical intermediate, resulting in formation of a new C–ligand bond with concomitant single electron reduction of the metal

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• resulting in two different ligand coupling outcomes. While most of their reactions expel an iodoarene to produce functionalized β-dicarbonyl motifs, ligand coupling with the arene motif is also possible, such as in the (radio)fluorination of iodonium ylides. Finally, intramolecular σ-hole bonding offers the

• analogous free-carbene mediated reactions, and they instead proposed iodine to have engaged with Lewis basic ligands and coordinated their coupling within its ligand sphere. An ylide’s positively charged iodine was consistently proposed to accept ligands, via either concerted or ionic steps, ultimately

• such that they can undergo intramolecular reactions within the iodine’s ligand sphere. These EDA complexes have been proposed to then undergo single electron transfers from the Lewis base to the ylide, under both thermal or blue LED irradiation conditions, leading to C–H insertion products. Irradiating

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• cycle nor ii) *[Ir1]0 via a conPET mechanism. Rather, changes related to a chemical transformation of the dtbbpy ligand of the catalyst under the reaction conditions. Charge neutrality and diamagnetism of the new catalyst species, as well as loss of the C2v symmetry of [Ir1]+, indicated the nonsymmetric

• transformation of the dtbbpy ligand to a monoanionic ligand. Extensive NMR analysis confirmed that upon the formation of [Ir1]0 via SET from Et3N to *[Ir1]+, partial saturation of the dtbbpy ligand generates [Ir2]0 and initiates the second catalytic cycle (Figure 17A). Upon excitation with blue light, *[Ir2]0

• excited state lifetimes [95][96], most reactions employing such photocatalysts require special reaction design (e.g., coordination of substrates as ligands to enable intramolecular metal to ligand charge transfer (MLCT)). Only recently have a few examples been reported that observed bimolecular quenching

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• tuning of the ligand and base combinations [18][19]. Thereafter, copper-catalyzed C–N bond-formation reactions have experienced unprecedented development due to mild reaction conditions and the low cost of copper salts [20][21][22]. On the other hand, hypervalent iodine reagents serve as versatile tools

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• chelate environmental Fe3+. Ligand groups, such as hydroxamate, phenolate, catecholate, carboxylate, or oxazoline/thiazoline residues, confer siderophores their high affinity for the binding of Fe3+ [3][4][5]. Following the coordination of the metal, the Fe3+-loaded siderophore complex is transported back

• for microbial communication processes [8]. Another unusual siderophore, gramibactin, is released by the rhizosphere bacterium Paraburkholderia graminis [9]. Gramibactin features an extremely rare diazeniumdiolate ligand with potent complexing properties [9][10]. Noteworthy is also bolagladin from

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• 10.3762/bjoc.19.65 Abstract We present here a stereoselective tandem reaction based on the asymmetric conjugate addition of dialkylzinc reagents to unsaturated acylimidazoles followed by trapping of the intermediate zinc enolate with carbocations. The use of a chiral NHC ligand provides chiral zinc

• . Results and Discussion For initial experiments, we have selected the conjugate addition of Me2Zn to acylimidazole 1a catalyzed by a chiral NHC ligand derived from imidazolium salt L1. This NHC precursor has been described previously by Gérard, Mauduit, Campagne and co-workers [19]. The ligand L1 is

• , the configuration at the position C-3 is determined by the chiral ligand L1 and was determined previously as (R) [19]. To gain insight into the reactivity of enolates formed in this transformation, we evaluated properties of Zn enolates by DFT calculations (Figure 2). The corresponding (E) and (Z

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• frameworks (MOFs) [16][54] has allowed the dynamics of the different counterparts in the solid state, as well as some advanced applications [55][56][57][58][59][60][61]. Berna and colleagues prepared a copper-organic framework (UMUMOF-(E)-3) containing the interlocked fumaramide (E)-3 as the organic ligand

• maleamides (Z)-3 in the solid state (Figure 3a), leading to an enhancement in the porosity of the metal-organic crystalline material. Noteworthy, a MOF having (Z)-3 as the only ligand was also prepared, showing a faster rotational dynamics of the threads within the crystalline array compared to that of

• atoms. The key colour of the cartoon representation is analogous to that of the chemical structures. Stick representations of the solid structures of: (a) U-CB[8]-MPyVB showing an interlocked ligand connected to two uranium clusters; and (b) the intertwined photodimerized product within the crystalline

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• challenge. In this context, a regioselective alkylation of ortho-unsubstituted or substituted unactivated pyridines with acrylates and acrylamides under Rh(I) catalysis has been demonstrated by Ellman and co-workers [59]. The authors observed that in the presence of [Rh(cod)Cl]2 as catalyst, dppe as ligand

• use of ligand dArFpe at reduced reaction temperature resulted in a significant increase in the yield of the branched alkylated product 41 (Scheme 9, reaction conditions c) compared to using the ligand dppe (Scheme 9, reaction conditions b). Moreover, when ethyl methacrylate was used as the coupling

• metals inhibits the metal–chiral ligand coordination, thus making the C–H alkylation of pyridine substrates challenging. In addition, transition-metal-catalyzed enantioselective C–H alkylation reactions of pyridine still remain a great challenge. In this regard, in 2022, Ye and co-workers [60] reported

Palladium-catalyzed enantioselective three-component synthesis of α-arylglycine derivatives from glyoxylic acid, sulfonamides and aryltrifluoroborates

• Bastian Jakob,
• Nico Schneider,
• Luca Gengenbach and
• Georg Manolikakes

Beilstein J. Org. Chem. 2023, 19, 719–726, doi:10.3762/bjoc.19.52

• corresponding R,R-iPrBox-ligand the second enantiomer, (R)-arylglycine 10l could be prepared with a similar yield and enantioselectivity. Conclusion In summary, we have reported a palladium-catalyzed enantioselective three-component reaction of aryltrifluoroborates, sulfonamides, and glyoxylic acid. This method

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• disorders) [16] (Figure 2). 10,11-Dihydrodibenzo[b,f]azepine-based ligand 7 and a methyl analogue thereof are known to form pincer complexes with Pd, Ir, Rh and Ln [5], whereas a copper(II) wagon wheel complex of 8 was reported in a molecular organic framework (MOF) (Figure 3) [6]. 4,4'-(5-(Pyridin-2-yl

• the synthesis of intermediate stilbenes 61 by Wittig coupling. The authors elected to use a Pd2dba3/DPEphos (L4)/Cs2CO3 system (dba = dibenzylideneacetone; DPEphos = bis[(2-diphenylphosphino)phenyl] ether) in toluene after catalyst and ligand screening. Cyclisation of several substituted 2,2

• final Mizoroki–Heck reaction will be discussed in the following section. The Buchwald group [59] reported a ligand-controlled divergent synthesis involving intramolecular cyclisation, allowing for the formation of several heterocycles, including dibenzo[b,f]azepines 89, in two steps. Screening of

Enolates ambushed – asymmetric tandem conjugate addition and subsequent enolate trapping with conventional and less traditional electrophiles

• Péter Kisszékelyi and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 593–634, doi:10.3762/bjoc.19.44

• high diastereoselectivity and good to excellent yields. In most cases, the authors detected only a single diastereomer in the crude reaction mixture (NMR). Using the enantiomeric form of the ligand or the chiral sulfoximine reagent, four diastereomeric β-aminoketones can be produced in excellent

• stereoselective methodologies have been published that demonstrate the Cu- or Ni-catalyzed conjugate addition of organozincs to α,β-unsaturated ketones 14 followed by the reaction of the metal enolate with a nitroolefin (20) (Table 1) [30][31][32][33]. These reactions were facilitated by different ligand families

• –Jung vinylsilane reagents 33. Kawamura et al. performed zinc enolate trapping reactions using ligand L10, a chiral quinoline-based N,N,P-ligand (Scheme 8A) [35]. The authors have concluded that the strict control of the amount of organozinc reagent added is essential to avoid side-product formation

C3-Alkylation of furfural derivatives by continuous flow homogeneous catalysis

• Grédy Kiala Kinkutu,
• Catherine Louis,
• Myriam Roy,
• Juliette Blanchard and
• Julie Oble

Beilstein J. Org. Chem. 2023, 19, 582–592, doi:10.3762/bjoc.19.43

• . Unfortunately, with this catalyst, repeatability problems were detected (yield fluctuation of approximately 20%) which could be assigned to the low solubility of this catalyst in toluene. In order to overcome these problems, we synthesized triruthenium carbonyl complexes with phosphine ligand(s), namely

• Information File 1 for the reaction kinetic curves of catalysts). In addition, the catalyst with a single L1 ligand (comp1) was found to be more reactive than the one with two ligands (comp2), and was therefore selected for further optimization. In contrast, comparison of its reaction kinetic curve with that

• °C in toluene for 1 h with 0.33 equiv of comp4 [Ru3(CO)11(PPh3)], a catalyst analogue to comp1 but bearing a less expensive phosphine ligand (Scheme 5A). The chosen ratio of imine to catalyst was consistent with the stoichiometric amounts needed to form the postulated intermediate. The temperature of

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• Alena V. Dmitrieva Oleg A. Levitskiy Yuri K. Grishin Tatiana V. Magdesieva Lomonosov Moscow State University, Dept. of Chemistry, Leninskie Gory 1/3, Moscow 119991, Russia 10.3762/bjoc.19.41 Abstract A new oxidatively stable (S)-N-benzylproline-derived ligand ((S)-N-(2-benzoyl-5-tert-butylphenyl

• complex. Solubility of the t-Bu-containing ligand and its Schiff base complexes is increased, facilitating scaling-up the reaction procedure and isolation of the functionalized amino acid. Keywords: asymmetric synthesis; chiral auxiliaries; cysteine derivatives; Ni–Schiff base complexes; voltammetry

• ][17][18]). In early works, the chiral tridentate ligand based on (S)-N-benzylproline (L1) was used [19][20]. Though the original Belokon complex derived from N-benzylproline and o-aminobenzophenone showed sufficiently high efficiency and is still the most widely used template, considerable efforts on

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• electrostatic binding of the dye along the polynucleotide backbone. The reorganized intramolecular conformation of the ligand could explain the quenching of excimer fluorescence and/or redistribution of chromophore charges upon binding since fluorescence quenching is sensitive to factors that affect the rate

• -site binding model (Figure 7, Table 3). ITC experiments confirmed the binding of the ligand with human DPP III mutant E451A. The experiment resulted in positive peaks as a result of an endothermic reaction, which took place with an increase in entropy (Figure 7C, Table 3). This means that the binding

• the ligand was stacked prior to binding, and unstacked during binding, so entropic loss relating with ligand flexibility was avoided upon binding. Interestingly, the guanidiniocarbonylpyrrole–phenanthridine conjugate bound to human DPP III mutant E451A with the similar thermodynamical pattern as Phen