A dynamic combinatorial library for biomimetic recognition of dipeptides in water

• Florian Klepel and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2020, 16, 1588–1595, doi:10.3762/bjoc.16.131

• slightly alkaline buffer (pH 7.4). An excess of our target molecules, the simple dipeptides AA, FF and YY (Y for tyrosine), were added to one sample each. An additional sample without dipeptide addition served as reference. After several hours of stirring in an open vial the thiol functions of the

• cysteines are converted quantitively to disulfides by oxidation with oxygen. Until fully oxidized library members can exchange building blocks in a thiol–disulfide exchange reaction. While a closed monomer can be observed in the beginning (Figure S1, Supporting Information File 1), exclusively cyclic

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• to the enone 63 and posterior hydrogen transfer from thiol to the intermediate 64 forms the ketone intermediate 65 (pathway 1). This ketone intermediate 65 is also accessible by an ionic addition in the dark (pathway 2). The tautomerization of the ketone 65 yields the enol form 66, which reacts with

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• tritiation of biologically relevant compounds using D2O and T2O as hydrogen isotope sources (Scheme 9) [60]. The SET oxidation of the thiol cocatalyst 9.2, triggered by the excited photocatalyst 4CzIPN (OD6), generates a sulfur-centered radical capable of driving the HAT process with the substrate 9.1. The

• trapping of the ensuing C(sp3) radical with the deuterated or tritiated thiol results in the incorporation of deuterium or tritium in multiple positions within the product 9.3. C(sp2) radicals Aryl radicals Considering the importance of arylation reactions in organic synthesis [61], aryl radicals are

• (Scheme 3 and Scheme 9) [41][60]. In stoichiometric amounts, they generally add efficiently to π-systems and can be applied in thiol-ene reactions. Recently, Dilman and co-workers published a hydrosulfenylation of the β-difluorostyrenes 41.2 for the synthesis of the thioethers 41.3 using 9-PhAcr (OD1) as

Copper-based fluorinated reagents for the synthesis of CF₂R-containing molecules (R ≠ F)

• Louise Ruyet and
• Tatiana Besset

Beilstein J. Org. Chem. 2020, 16, 1051–1065, doi:10.3762/bjoc.16.92

• ][30][31][32], a well recognized alcohol and thiol bioisoster, is particularly attractive due to its unique features [33][34][35][36]. Besides, this residue is present in several bioactive compounds such as Deracoxib and Thiazopyr. In comparison with trifluoromethylcopper complexes, the

Preparation and in situ use of unstable N-alkyl α-diazo-γ-butyrolactams in Rh^II-catalyzed X–H insertion reactions

• Maria Eremeyeva,
• Daniil Zhukovsky,
• Dmitry Dar’in and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2020, 16, 607–610, doi:10.3762/bjoc.16.55

• led to decomposition of the diazo compounds 4a–c), and addition of an alcohol, a thiol, or an aromatic amine along with a RhII catalyst resulted in a rapid insertion reaction and the isolation of the desired α-substituted γ-lactams 7a–o in modest yields (Scheme 1). It should be noted that, after some

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• magnetic nanoparticles Cl@CuFe2O4 (127). Subsequently, starch (128) was reacted with (3-mercaptopropyl)triethoxysilane in dry toluene to afford the starch-containing thiol-functionalized nanoparticles SH@starch (129). Next, 127 was grafted onto 129 in toluene at reflux conditions for 24 h to form the

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• with thiol moieties such as phenylmercapto and phenylmercapto-tetrazole substituents resulted in Φf of 7% (compare 64–68) and 3% (compare 78), respectively. Thus, one can roughly draw the following order for the decrease fluorescence quantum yields located at the meso-position: PhO-; Ph- ≥ barbiturate

Synthesis, liquid crystalline behaviour and structure–property relationships of 1,3-bis(5-substituted-1,3,4-oxadiazol-2-yl)benzenes

• Afef Mabrouki,
• Malek Fouzai,
• Armand Soldera,
• Abdelkader Kriaa and
• Ahmed Hedhli

Beilstein J. Org. Chem. 2020, 16, 149–158, doi:10.3762/bjoc.16.17

• thiol one 3b. The observed IR absorptions at 3387 cm−1 (νN-H) and 1263 cm−1 (νC=S) and the absence of absorptions in the 2600–2550 cm−1 region (νS-H) support the preference for the thione form in solution. This latter is obviously more solvated than thiol. Liquid crystal properties The structure of

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• , which showed half-lives ranging from 50 ms [25] to a few seconds [26][27]. Instead, compounds 4 and 5 exhibited photoswitching properties similar to those reported for tetra-ortho-thiol-substituted azobenzenes [17]. Conclusion Substitution of p-aminoazobenzene with ortho-bromo and ortho-methoxy groups

SnCl₄-catalyzed solvent-free acetolysis of 2,7-anhydrosialic acid derivatives

• Kesatebrhan Haile Asressu and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2019, 15, 2990–2999, doi:10.3762/bjoc.15.295

• can be transformed smoothly into thioglycoside [15][16][35] and sialyl halide [38][39] donors when treated with a thiol in the presence of triflic acid, BF3⋅OEt2, and HCl, respectively. Through comparison with the reported mechanism of Sc(OTf)3-catalyzed acetolysis of 1,6-anhydro-β-hexopyranoses [32

Chemical tuning of photoswitchable azobenzenes: a photopharmacological case study using nicotinic transmission

• Lorenzo Sansalone,
• Jun Zhao,
• Matthew T. Richers and
• Graham C. R. Ellis-Davies

Beilstein J. Org. Chem. 2019, 15, 2812–2821, doi:10.3762/bjoc.15.274

• absence of any thiol, the maleimide functionality was reasonably stable, with 80% hydrolysis occurring over 22 h (Figure S3, see also LC–MS in Supporting Information File 1). Reassured by these data, 1 was mixed with a stoichiometric amount of glutathione, at 37 °C rapid reaction gave peak with a shorter

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• chloroperoxidase catalyst. H2O2 generated in situ from the cathodic reduction of oxygen was proposed to be responsible for the enzyme-mediated thiol ether oxidation (Scheme 47) [82]. Vitamin B12-dependent enzymes are an exciting representative in the family of chiral inductors for electroorganic chemistry. These

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• covalently conjugates thiol groups of cysteine residues in proteins or peptides by the thio-Michael addition to the double bond of the maleimide to form a corresponding succinimidyl thioether. Conjugation of the cysteine sulfhydryl group with maleimide moieties allows us to prepare the bioconjugates

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

A novel three-component reaction between isocyanides, alcohols or thiols and elemental sulfur: a mild, catalyst-free approach towards O-thiocarbamates and dithiocarbamates

• András György Németh,
• György Miklós Keserű and
• Péter Ábrányi-Balogh

Beilstein J. Org. Chem. 2019, 15, 1523–1533, doi:10.3762/bjoc.15.155

• elemental sulfur and NaH generates a polysulfide anion that is able to attack the carbenoid carbon atom of isocyanide 1a yielding the isothiocyanate intermediate 8. Then, the present nucleophile (NuH, alcohol or thiol) undergoes a nucleophilic addition on 8 providing thiocarbamate 3a. Conclusion In summary

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• of the thiol addition [24]. In analogy to this reaction, the insertion of 1 into disulfide bonds has been discovered early, but only very few examples can be found in the literature [10][11][25][26][27][28]. In this work, the insertion of [1.1.1]propellane (1) into disulfide bonds was investigated

• formation of the 4-methoxybenzenethiyl radical, but the values are in the same region. To ascertain the main factor for this trend further investigations are necessary. We observed the same trend in the thiol addition to 1, when thiophenol and 4-methoxythiophenol were used in a competitive reaction [24

Synthesis of aryl cyclopropyl sulfides through copper-promoted S-cyclopropylation of thiophenols using cyclopropylboronic acid

• Emeline Benoit,
• Ahmed Fnaiche and
• Alexandre Gagnon

Beilstein J. Org. Chem. 2019, 15, 1162–1171, doi:10.3762/bjoc.15.113

• ) [21][22]. While these methods give access to highly substituted products, the requirement for a strong base could jeopardize their application in the context of synthesis of complex molecules. Furthermore, an electron-withdrawing group must be present on 18 to enable the Michael addition with thiol 14

Towards the preparation of synthetic outer membrane vesicle models with micromolar affinity to wheat germ agglutinin using a dialkyl thioglycoside

• Dimitri Fayolle,
• Nathalie Berthet,
• Bastien Doumeche,
• Olivier Renaudet,
• Peter Strazewski and
• Michele Fiore

Beilstein J. Org. Chem. 2019, 15, 937–946, doi:10.3762/bjoc.15.90

• , DCM UMR 5250, F-38000 Grenoble, France 10.3762/bjoc.15.90 Abstract A series of alkyl thioglycosides and alkyl thiodiglycosides bearing glucose and N-acetylglucosamine residues were prepared by thiol–ene coupling in moderate to good yields (40–85%). Their binding ability towards wheat germ agglutinin

• addition of thiols to alkenes – known as thiol–ene coupling, TEC – a very efficient metal-free click reaction [18][19]. We prepared n-alkyl 1-thio-β--glycosides from unprotected sugar anomeric thiols, commercial n-alkenes and one synthetic lipophilic scaffold presenting two reactive alkenyl ends. Although

• thiyl-radical-mediated reactions have been extensively investigated for the preparation of carbohydrate derivatives [20] and some dithioether phospholipid and glycolipid analogues [21][22], no examples were reported for the synthesis of n-alkyl thioglycosides by using thiol–ene coupling [18][19]. In

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• shaking and stirring [89]. Peptide-chain containing distal thiol groups underwent an aerial oxidation process to give different disulfide-containing macromolecules. They observed that under mechanical shaking conditions preferentially the cyclic hexamer 33 is formed, whereas stirring resulted in formation

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• the parent benzene chromophore utilizing Clar’s notation [26], assuming that the electron-donating alkyl and thiol substituents exert a bathochromic effect. The spectral properties of the nickel complexes differ from those of the zinc and cadmium counterparts in that they exhibit two additional

Thiol-free chemoenzymatic synthesis of β-ketosulfides

• Adrián A. Heredia,
• Martín G. López-Vidal,
• Marcela Kurina-Sanz,
• Fabricio R. Bisogno and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2019, 15, 378–387, doi:10.3762/bjoc.15.34

• ; sulfoxide; thiol-free; Introduction Throughout the years, several strategies have been developed to build up organic compounds bearing a sulfide moiety [1][2]. Often, thiols (or the corresponding thiolate anions) are employed as nucleophilic sulfur reagents in order to react with a suitable electrophile [3

• ][4], however, there are certain negative aspects of thiols that need to be taken into account (i.e., foul smell, easy oxidation into disulfide, participation as donors in one-electron events, reaction with olefins through ene-type reactions, etc) [5][6][7][8]. Hence, the development of thiol-free

• further preparation of valuable ketosulfoxides and ketosulfones. Selected examples of valuable β-ketosulfides. A: bioactive synthetic compounds, B: natural products. Time-course plot for the CAL-B catalysed hydrolysis of 1a. Different strategies for the preparation of β-ketosulfides. Thiol-free

Metal-free C–H mercaptalization of benzothiazoles and benzoxazoles using 1,3-propanedithiol as thiol source

• Yan Xiao,
• Bing Jing,
• Xiaoxia Liu,
• Hongyu Xue and
• Yajun Liu

Beilstein J. Org. Chem. 2019, 15, 279–284, doi:10.3762/bjoc.15.24

• -catalyzed C–H thiolation of benzothiazole or benzoxazole with a disulfide and a thiol provides easy access to the corresponding sulfides [26][27][28][29][30][31][32][33][34]. However, the examples using C–H functionalization for preparing 2-mercaptobenzoxazoles or 2-mercaptobenzothiazoles are still rare. In

• 2009, the Daugulis group reported that benzoxazole was converted to 2-mercaptobenzoxazoles in the presence of sulfur and potassium tert-butoxide, but only one example was shown [35]. In 2017, the Lei group reported a copper catalyzed C–H mercaptalization strategy using elementary sulfur as thiol source

• benzoxazoles to the corresponding thiols through direct C–H mercaptalization using 1,3-propanedithiol as thiol source. Results and Discussion Previous studies in our group revealed that small aliphatic diols and dithiols are promising reagents for the synthesis of phenols and arylthiols, respectively [23][37

Synthesis of a tubugi-1-toxin conjugate by a modulizable disulfide linker system with a neuropeptide Y analogue showing selectivity for hY1R-overexpressing tumor cells

• Rainer Kufka,
• Robert Rennert,
• Goran N. Kaluđerović,
• Lutz Weber,
• Wolfgang Richter and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2019, 15, 96–105, doi:10.3762/bjoc.15.11

• )-inspired peptide [K4(C-βA-),F7,L17,P34]-hNPY, acting as NPY Y1 receptor (hY1R)-targeting peptide, to form a tubugi-1–SS–NPY disulfide-linked conjugate. The cytotoxic impacts of the novel tubugi-1–NPY peptide–toxin conjugate, as well as of free tubugi-1, and tubugi-1 bearing the thiol spacer (liberated from

• potency of the liberated tubugi-1 that, however, still bears the thiol spacer (tubugi-1-SH) was restored and up to 10-fold higher compared to the entire peptide–toxin conjugate. The conjugate shows toxic selectivity to tumor cell lines overexpressing the hY1R receptor subtype like, e.g., the hard to treat

• -1)-βA),F7,L17,P34]-hNPY (8), was synthesized by reacting the tubugi-1-SSPy (3) with the free thiol function of a β-alanine–cysteine dipeptide (βAC) linked to the side chain of Lys4 of the targeting peptide. For this purpose, 1 mol equiv of the tubugi-1-SSPy building block 3 and one molar equivalent