Photocatalyzed elaboration of antibody-based bioconjugates

• Marine Le Stum,
• Eugénie Romero and
• Gary A. Molander

Beilstein J. Org. Chem. 2025, 21, 616–629, doi:10.3762/bjoc.21.49

• additionally generate an undesirable new stereocenter [26][27]. Few methods have been developed for the functionalization of tyrosine (Tyr) and tryptophan (Trp). With a low abundance (≈3%) in proteins, Tyr modifications are widely recognized for their ability to profoundly impact protein properties and

• of sensitive residues such as tryptophan (Trp), tyrosine (Tyr), cysteine (Cys), and histidine (His), as well as partial unfolding of the antibodies, exposing hydrophobic regions that promote nonspecific interactions and aggregate formation. Additionally, covalent cross-links may form, involving

Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

• Gianpaolo Gallo and
• Bartosz Lewandowski

Beilstein J. Org. Chem. 2025, 21, 541–546, doi:10.3762/bjoc.21.42

• Gianpaolo Gallo Bartosz Lewandowski Laboratory of Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093 Zürich, Switzerland 10.3762/bjoc.21.42 Abstract Tryptophan fulfills a plethora of important functions in nature both in its free form and as a component of peptides and proteins. Selective

• binding of tryptophan is therefore important for diagnostic and medicinal applications. Recently, we reported a glucose naphtho crown ether which is a chemoselective receptor for the esters of aromatic amino acids, in particular tryptophan, in water. Herein, we demonstrate that the same compound also

• binds free tryptophan selectively in aqueous media. Furthermore, it is capable of binding to tryptophan within model tripeptides. The naphthalene functionality in the glucose-derived receptor enables the study of guest binding using fluorescence spectroscopy. Keywords: amino acids; macrocyclic

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels

• Connor R. M. MacDonald and
• Emily R. Draper

Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220

• supramolecular helices [45]. SEM was used to investigate the structures resulting from the self-assembly of a bis-bipyridinium-based compound (1·4Br) resulting in helical supramolecular fibres with different chirality induced depending on the enantiomer of tryptophan present. The direct images obtained from SEM

• allowed the chirality of the resulting fibres to be easily observed, indicating that the hydrogel matrix induced by racemic tryptophan was comprised of racemic amounts of left-handed (M) and right-handed (P) helices (Figure 8) [45]. Due to the orientational averaging of scattering techniques, directional

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• [70]. The mildness of this reaction was demonstrated through the late-stage C–H trifluoromethylation of ascapheine, pentoxifylline, doxophylline, theobromine, methylethrone, and tryptophan derivatives. During the reaction, irradiation of the organic dye Mes-Acr+ leads to the formation of its oxidized

Computational toolbox for the analysis of protein–glycan interactions

• Ferran Nieto-Fabregat,
• Maria Pia Lenza,
• Angela Marseglia,
• Cristina Di Carluccio,
• Antonio Molinaro,
• Alba Silipo and
• Roberta Marchetti

Beilstein J. Org. Chem. 2024, 20, 2084–2107, doi:10.3762/bjoc.20.180

• mannose (Man) directly binds a tryptophan residue [30]; iv) the covalent attachment to core protein of glycosaminoglycans (GAGs), anchored to a Ser, or at lesser extent to Thr or Asn, forms proteoglycans. GAGs are complex negatively charged polysaccharides composed by disaccharide repeats of GlcNAc or

2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• solute carrier protein which is used as strategic target for blood–brain-barrier drug delivery. In general, the authors found the compounds less potent than the natural substrate ʟ-tryptophan, with exception of derivative 112 (Scheme 17). Tetrazoles: Taking advantage of using tetrazoles not as a phenyl

Methyltransferases from RiPP pathways: shaping the landscape of natural product chemistry

• Maria-Paula Schröder,
• Isabel P.-M. Pfeiffer and
• Silja Mordhorst

Beilstein J. Org. Chem. 2024, 20, 1652–1670, doi:10.3762/bjoc.20.147

• first RiPP to be isolated from Myxobacteria. It was specifically isolated from Chondromyces crocatus Cm C5. The core peptide is composed of only three amino acids: isoleucine, tyrosine, and tryptophan. It forms a tetracyclic core system that contains a tetrahydropyrroloindoline, which is unprecedented

• thiostrepton A, which is known to be produced by different Streptomyces strains [126][127]. During the maturation of thiostrepton A, a quinaldic moiety is formed from tryptophan. TsrM catalyses the initial step by transferring a methyl group from SAM to the electrophilic carbon atom C2 of tryptophan. In the

Mining raw plant transcriptomic data for new cyclopeptide alkaloids

• Draco Kriger,
• Michael A. Pasquale,
• Brigitte G. Ampolini and
• Jonathan R. Chekan

Beilstein J. Org. Chem. 2024, 20, 1548–1559, doi:10.3762/bjoc.20.138

• tryptophan at the position for cyclization, indicating they may correspond to the stephanotic acid-type burpitides like moroidin (Trp-indole-C to carbon crosslink, Figure 3) [4]. Amaranthaceae family The Amaranthaceae family is home to the known moroidin producer, Celosia argentea var. cristata (Cockscomb

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• -(−)-tryptophan via the common intermediate, (+)-vellosimine (74). The protocol reflected the stereocontrolled formation of the C-16 quaternary center in 76 created via an intermolecular crossed-Cannizzaro reaction of 75, generated from 74, using 37% aqueous formaldehyde. The quaternization proceeded in excellent

Chemical and biosynthetic potential of Penicillium shentong XL-F41

• Ran Zou,
• Xin Li,
• Xiaochen Chen,
• Yue-Wei Guo and
• Baofu Xu

Beilstein J. Org. Chem. 2024, 20, 597–606, doi:10.3762/bjoc.20.52

• ]. Recent studies have revealed that certain fungi are also prolific sources of indole alkaloids, which are among the largest classes of nitrogen-containing secondary metabolites. Characterized by at least one indole moiety and derived from tryptophan or tryptamine, indole alkaloids are known for their

• cytochrome P450, pyridoxal-dependent decarboxylase, glutamine synthase, and tryptophan dimethyltransferase (Figure 5). These genes are likely crucial for the biosynthesis of the newly isolated alkaloids, 1 and 2. In examining the XL-F41 genome for methyltransferase domain-containing BGCs, we found a

• methyltransferase near BGC 7.3, suggesting its involvement in adding a methoxy group at the C16 position of compound 1. From these key enzyme genes, we propose a hypothetical biosynthetic pathway (Figure 5). Compounds 1 and 2 are hypothesized to be synthesized from a tryptophan precursor via a shared biosynthetic

Discovery of unguisin J, a new cyclic peptide from Aspergillus heteromorphus CBS 117.55, and phylogeny-based bioinformatic analysis of UngA NRPS domains

• Sharmila Neupane,
• Marcelo Rodrigues de Amorim and
• Elizabeth Skellam

Beilstein J. Org. Chem. 2024, 20, 321–330, doi:10.3762/bjoc.20.32

• , 7.33, 7.07 and 6.97 ppm, exhibiting key 1H,1H-COSY and HMBC correlations, suggested a tryptophan aromatic amino acid portion (Figure 3). The other six amino acid residues were assigned based on 2D NMR spectra (1H-1H COSY, HSQC and HMBC) as Ala (2 equiv), Phe (1 equiv), Leu (1 equiv), Val (1 equiv), and

• authentic amino acid samples determined the structure of 1 as cyclo(ᴅ-alanine-ᴅ-valine-ʟ-leucine-ᴅ-phenylalanine-ᴅ-alanine-ᴅ-tryptophan-GABA). Compound 1 was named as unguisin J. A second peptide was isolated from the same culture of A. heteromorphus CBS 117.55. Compound 2 was obtained as an amorphous white

Photoredox catalysis enabling decarboxylative radical cyclization of γ,γ-dimethylallyltryptophan (DMAT) derivatives: formal synthesis of 6,7-secoagroclavine

• Alessio Regni,
• Francesca Bartoccini and
• Giovanni Piersanti

Beilstein J. Org. Chem. 2023, 19, 918–927, doi:10.3762/bjoc.19.70

• carboxylate anion and/or reduction of the corresponding N-hydroxyphthalimide- (NHPI)-derived redox-active ester, although it destroys their stereochemical information [46][47][48][49][50][51]. In addition, the side-chains of aromatic amino acids (mainly electron-rich tryptophan and tyrosine) can be

• selectively targeted by photoredox catalysis to enable unprecedented modification of the amino acid. In this context, it is worth mentioning that the single-electron oxidation of the indole moiety in tryptophan provides the radical cation, which enables selective C-radical generation at the weaker benzylic

• position via a sequential electron transfer–proton transfer (ET/PT) [52][53][54][55][56][57][58][59]. With our ongoing interest of establishing new methods for the asymmetric synthesis of nonproteinogenic tryptophan derivatives as well as their associated indole alkaloid natural products [60][61][62][63

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• , partial least square (PLS) modeling was used for the determination of the composition of solutions containing tryptophan methyl ester, phenylalanine, norephedrine, N,N’-bis-(α-methylbenzyl)sulfamide, sulfaguanidine or sulfamethoxazole using the spectral data of the corresponding CD host–guest complexes

Synthesis of tryptophan-dehydrobutyrine diketopiperazine and biological activity of hangtaimycin and its co-metabolites

• Houchao Xu,
• Anne Wochele,
• Minghe Luo,
• Gregor Schnakenburg,
• Yuhui Sun,
• Heike Brötz-Oesterhelt and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1159–1165, doi:10.3762/bjoc.18.120

• , People's Republic of China Institute of Inorganic Chemistry, University of Bonn, Gerhard-Domagk-Straße 1, 53121 Bonn, Germany 10.3762/bjoc.18.120 Abstract An improved synthesis for tryptophan-dehydrobutyrine diketopiperazine (TDD), a co-metabolite of the hybrid polyketide/non-ribosomal peptide

• hangtaimycin, starting from ʟ-tryptophan is presented. Comparison to TDD isolated from the hangtaimycin producer Streptomyces spectabilis confirmed its S configuration. The X-ray structure of the racemate shows an interesting dimerisation through hydrogen bridges. The results from bioactivity testings of

• ]. Another hangtaimycin co-metabolite in S. spectabilis [9] is tryptophan-dehydrobutyrine diketopiperazine (TDD, 4) that was already isolated several decades before the discovery of 1, and likewise reported to have no antibacterial activity [9]. The initially published structure was that of (E)-4 [9], but

Morita–Baylis–Hillman reaction of 3-formyl-9H-pyrido[3,4-b]indoles and fluorescence studies of the products

• Nisha Devi and
• Virender Singh

Beilstein J. Org. Chem. 2022, 18, 926–934, doi:10.3762/bjoc.18.92

• large number of natural products are reported representing this scaffold [9][10][11][12][13][14][15][16]. The key precursor used in the biosynthesis of β-carboline is ʟ-tryptophan which forms the basis of great abundance of β-carboline-containing natural products [17]. A broad spectrum of biological

• ) condensation of ʟ-tryptophan (1) with different aldehydes (a–e) in dry DCM at room temperature yielded tetrahydro-β-carboline derivatives 2a–e, which were then oxidized with KMnO4 in anhydrous DMF for 45 minutes to yield β-carboline derivatives 3a–e. It was encouraging to observe that the P-S condensation with

• ʟ-tryptophan (1) was much faster than with the tryptophan ester, taking only 45 minutes to complete. Interestingly, KMnO4 oxidation was selective, with no decarboxylation seen. Within 15 minutes, further treatment of 3a–e with methyl iodide in the presence of K2CO3 provided the corresponding methyl

Efficient production of clerodane and ent-kaurane diterpenes through truncated artificial pathways in Escherichia coli

• Fang-Ru Li,
• Xiaoxu Lin,
• Qian Yang,
• Ning-Hua Tan and
• Liao-Bin Dong

Beilstein J. Org. Chem. 2022, 18, 881–888, doi:10.3762/bjoc.18.89

• produce IPP and DMAPP [19][20][21]. Notably, this pathway successfully bypassed the limitations of native isoprenoid biosynthetic pathways, resulting in the overproduction of multiple (mero)terpenoids such as lycopene, cis-abienol, and prenylated tryptophan [15][19][22][23]. The clerodane and ent-kaurane

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• peptide macrocyclisation of the two above mentioned side chain residues of the natural amino acids. However, these Pd-mediated stapling reactions were performed only on an analytical scale and the secondary structures of the cyclic peptides were not studied. Since tryptophan has only an incidence of about

• of macrocycles [49]. The macrocyclisation technique by tryptophan C2–H activation has been further improved showing structurally constrained peptides bearing a side chain connection of tryptophan and phenylalanine or tyrosine [50]. Moreover, a similar Pd-mediated approach for C(sp3)–H activation of

• phthaloyl-protected N-terminal alanine was also used for macrocyclisation in peptide stapling [51][52]. Besides addressing the indole C2, the regioselective enzymatic halogenation at C5, C6, or C7 using FAD-dependent tryptophan halogenases opens a broad area of Pd-catalysed late-stage diversifications [53

Unsaturated fatty acids and a prenylated tryptophan derivative from a rare actinomycete of the genus Couchioplanes

• Shun Saito,
• Kanji Indo,
• Naoya Oku,
• Hisayuki Komaki,
• Masashi Kawasaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2021, 17, 2939–2949, doi:10.3762/bjoc.17.203

• -octadienoic acid (5), and one prenylated tryptophan derivative, 6-(3,3-dimethylallyl)-N-acetyl-ʟ-tryptophan (6). The enantiomer ratio of 4 was determined to be approximately S/R = 56:44 by a recursive application of Trost’s chiral anisotropy analysis and chiral HPLC analysis of its methyl ester. Compounds 1–5

• were weakly inhibitory against Kocuria rhizophila at MIC 100 μg/mL and none were cytotoxic against P388 at the same concentration. Keywords: Couchioplanes; prenylated tryptophan; rare actinomycete; unsaturated fatty acid; Introduction Actinomycetes, a subgroup of filamentous Gram-positive bacteria

• -hydroxy-2,4,7-trimethyl-2,4-octadienoic acid (5), as well as one new prenylated tryptophan derivative, 6-(3,3-dimethylallyl)-N-acetyl-ʟ-tryptophan (6) (Figure 1). Results and Discussion The producing strain RD010705 was shake-cultured in A16 liquid medium at 30 °C for 8 days, and the whole culture was

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• and Dockendorf prepared the corresponding 2,2’-sulfur-substituted compounds 90 by reacting tryptophan amines 89 and 90 with S2Cl2 under neutral and acidic conditions, respectively (Scheme 11b and Scheme 11c) [77][78]. Kamal took a different approach using a CuO nanoparticle-supported graphene-oxide

• )-tryptophan amide 129 (Scheme 17a) [92]. Bis(indol-2-yl)selane 130 was found as a byproduct having very low such bioactivity. The polyselanes formed were separated by treating them with NaBH4, which did not affect the monoselane 130. On the other hand, selenopyrans structurally resemble indolocarbazoles

• opening attempt of chiral oxirane 153 in the presence of BF3.Et2O (Scheme 20) [104]. The synthetic route to the desired product was smoothly brought to its course by employing CuCN in the medium. Amines The enzymes indoleamine 2,3-dioxygenase 1 (IDO1) and tryptophan 2,3-dioxygenase (TDO) are responsible

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• full agonists (54 and 55, Scheme 20A) [139]. Ackermann and co-workers presented a manganese(I)-catalyzed C–H allylation, installing α,β-unsaturated esters in peptide analogues bearing indole motifs (Scheme 22B) [140]. Starting with tryptophan, the enantioselective allylation reaction afforded the

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• (19) is a tryptophan-derived indole alkaloid which was so far only shown to be produced by A. fumigatus while other fumigaclavines can for example also be found in Penicillium ssp. (fumigaclavine A (18) and B (17)) [66][158]. In all fungi, alkaloid biosynthetic pathways share a common basis, starting

• with the prenylation of ʟ-tryptophan to dimethylallyltryptophan (DMAT). During several steps DMAT is converted to chanoclavine-I aldehyde, the last mutual intermediate. Branching into different pathways after this intermediate is mainly due to differences in the function of EasA, the enzyme catalysing

• . They occur most often in Aspergillus and Penicillium species [160]. Fumitremorgin A (20), B (21) and C (22) can all be found in A. fumigatus (Figure 7). They are based on the precursers ʟ-tryptophan and ʟ-proline and are further derived from breviamide F, proposedly via tryprostatin B which is

Sustainable manganese catalysis for late-stage C–H functionalization of bioactive structural motifs

• Jongwoo Son

Beilstein J. Org. Chem. 2021, 17, 1733–1751, doi:10.3762/bjoc.17.122

• -economical approach to several tryptophan-containing peptides with significant potential for drug discovery and medicinal chemistry. Positional selectivity was observed at the C2 position due to the presence of the pyrimidine directing group. Interestingly, alkynylative conjugation of tryptophan to a steroid

• ]. Based on an initial optimization study, manganese(I) pentacarbonyl bromide was deemed as the optimal catalyst, enabling a robust racemization-free allylation process. In addition to tryptophan-containing peptides, diazepam and nucleoside analogues were found to be viable allylation substrates, affording

• peptide–carbohydrate conjugation was achieved using tryptophan-containing peptides 29 and sugar-containing allyl carbonates 30 in chemo- and site-selective manners using a pyridyl directing group. The optimized reaction conditions entailed the use of dimanganese decacarbonyl as the catalyst and sodium

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116