(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• reduction. Deprotection of the alcohol followed by two-step oxidation to the carboxylic acid yielded the non-natural β-amino acid (±)-50, which could then be transformed into diamine (±)-51 by Curtius rearrangement. Recently, Mykhailiuk and co-workers also reported the synthesis of 1,2-BCHs using an

• , respectively (Scheme 12B) [58]. Saponification of the ester moieties in these species followed by Curtius rearrangements then led to amines 114 and 116. Non-natural amino acid derivatives 113 and 117 are intermediates prepared using these methods that could be of interest to medicinal chemistry. Alcohol 111

Activity assays of NnlA homologs suggest the natural product N-nitroglycine is degraded by diverse bacteria

• Kara A. Strickland,
• Brenda Martinez Rodriguez,
• Ashley A. Holland,
• Shelby Wagner,
• Michelle Luna-Alva,
• David E. Graham and
• Jonathan D. Caranto

Beilstein J. Org. Chem. 2024, 20, 830–840, doi:10.3762/bjoc.20.75

• physiological function of NNG are discussed below. Results Screening of Vs NnlA homologs for NNG degradation activity To select Vs NnlA homologs to test for NNG degradation activity, we performed a BLAST search of the Vs NnlA amino acid sequence in the NCBI database. This search resulted in retrieval of 99

• homologous amino acid sequences with an E-value of less than 1 × 10−10. A subset of 55 of these sequences was selected with a query cover of greater than 88%. From these sequences, we selected five homologs of the nnlA gene [Pseudovibrio denitrificans JCM 1230 (Pd), Pseudovibrio japonicus strain KCTC 12861

• (Pj), Pseudonocardia spinosispora DSM 44797 (Ps), Mycobacterium sp. 1465703.0 (Ms), Microbispora rosea subsp. nonnitritogenes strain NRRL B-2631 (Mr)], which were synthesized and cloned into E. coli recombinant expression vectors. These homologs ranged in amino acid sequence identity from 46 to 76

Synthesis and characterization of water-soluble C₆₀–peptide conjugates

• Yue Ma,
• Lorenzo Persi and
• Yoko Yamakoshi

Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71

•  1). Results and Discussion Syntheses of C60–oligopeptides 5a–c The oligopeptides 2a–c were synthesized on resin using Fmoc-protected amino acids with a standard SPPS method (Figure 1a) [43]. A moderate loading (0.4 mmol⋅g−1) of the initial amino acid was used. After synthesizing the pentamer of Lys

• acid-substituted C60 derivative 3 and the peptides on resin 2a–c were performed by SPPS to provide the C60–oligopeptides on resin 4a–c (Figure 1a). Subsequently, the last step of the reaction – the cleavage of the C60–peptide conjugate from the resin and the simultaneous deprotection of the amino acid

• the C60–peptide conjugates on resin 4a–c from 2a–c. The C60–oligopeptides 5a–c were obtained by cleavage from resin and simultaneous deprotection of the PGs on the amino acid side chains through the addition of by the addition of a mixture of TFA and TIPS in water. The most soluble conjugate, C60

Substrate specificity of a ketosynthase domain involved in bacillaene biosynthesis

• Zhiyong Yin and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2024, 20, 734–740, doi:10.3762/bjoc.20.67

• understanding of polyketide biosynthesis has been reached, including a detailed knowledge of the extender unit selection and the stereochemical implications that are predictable from amino acid sequences [5][6]. The polyene antibiotic bacillaene was first isolated from Bacillus subtilis [7]. This soil-dwelling

• , showing that the amino acid sequences of these KSs correlate with the structures of the processed PKS intermediates up to the β-carbon [20]. 13C NMR spectra of (R)-11 incubated with BaeJ-KS2 and BaeJ-KS2-C222A. A) Free 11 dissolved in incubation buffer; B) (R)-11 bound to BaeJ-KS2 after incubation and

Chemoenzymatic synthesis of macrocyclic peptides and polyketides via thioesterase-catalyzed macrocyclization

• Senze Qiao,
• Zhongyu Cheng and
• Fuzhuo Li

Beilstein J. Org. Chem. 2024, 20, 721–733, doi:10.3762/bjoc.20.66

• several positions and also form 6–14 residue cyclic peptides [37][38]. It should be noted that TycC TE was more sensitive to the amino acid changes near the site of ring closure. The alkyne-containing analogs were conjugated to a variety of azido sugars via copper(I)-catalyzed cycloaddition to obtain the

• developed to address this challenge to produce daptomycin and its derivatives. These approaches include biosynthetic [49], chemoenzymatic [50], solid-phase [51], and solution-phase methods [52], but most only encompass modifications of the lipid chain and specific amino acid mutations. Learning from the

New variochelins from soil-isolated Variovorax sp. H002

• Jabal Rahmat Haedar,
• Aya Yoshimura and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2024, 20, 692–700, doi:10.3762/bjoc.20.63

• serine (Ser), a β-hydroxyaspartic acid (Hya), and a unique γ-amino acid biosynthetically originating from an arginine and a methyl malonate (4-amino-7-guanidino-3-hydroxy-2-methylheptanoic acid), with the amino group acylated by a saturated fatty acid. Subsequent HMBC and MS/MS analyses indicated that

• C45H79O17N11, as suggested by the HRESIMS data (m/z 1044.5603 for the [M − H]− ion), indicating the loss of two methylene groups (C2H4) from 1. In addition, the MS/MS fragmentation profile of 3 was consistent with those of 1 and 2, except for the loss of 28 mass units in the N-terminal Nγ-acyl-γ-amino acid

• ][18]. The absolute configurations of the amino acid constituents, Pro, Ser and two modified ornithine residues, in 3–5 were assigned as ʟ, ᴅ, and ʟ, respectively (Figures S25, S33, and S41, Supporting Information File 1). The geometry of the olefins in 4 and 5 was determined to be Z based on the 13C

Palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines

• Geng-Xin Liu,
• Xiao-Ting Jie,
• Ge-Jun Niu,
• Li-Sheng Yang,
• Xing-Lin Li,
• Jian Luo and
• Wen-Hao Hu

Beilstein J. Org. Chem. 2024, 20, 661–671, doi:10.3762/bjoc.20.59

• -light-mediated palladium-catalyzed three-component radical-polar crossover carboamination of 1,3-dienes or allenes with diazo esters and amines, affording unsaturated γ- and ε-amino acid derivatives with diverse structures. In this methodology, the diazo compound readily transforms into a hybrid α-ester

• -amino acid derivative. This approach proceeds under mild and simple reaction conditions and shows high functional group tolerance, especially in the incorporation of various bioactive molecules. The studies on scale-up reactions and diverse derivatizations highlight the practical utility of this

• temperature (rt), the desired unsaturated ε-AA derivative 4a was obtained in 75% isolated yield (Table 1, entry 1). Isolation and NMR analysis demonstrated that this model reaction provided amino acid 4a with good E-selectivity and excellent regioselectivity (E/Z = 91:9, 1,4-/1,2-addition >20:1). Control

A myo-inositol dehydrogenase involved in aminocyclitol biosynthesis of hygromycin A

• Michael O. Akintubosun and
• Melanie A. Higgins

Beilstein J. Org. Chem. 2024, 20, 589–596, doi:10.3762/bjoc.20.51

• . Interestingly, this cluster is separated into two groups. All the sequences that group with Hyg17 are found in identical hygromycin A biosynthetic clusters. The second group has 12 of the 29 Hyg genes with greater than 30% amino acid identity (Figure 4b and Supporting Information File 1, Table S2). The strains

Recent developments in the engineered biosynthesis of fungal meroterpenoids

• Zhiyang Quan and
• Takayoshi Awakawa

Beilstein J. Org. Chem. 2024, 20, 578–588, doi:10.3762/bjoc.20.50

• sequential reaction to produce the spirolactone 27. In contrast, PrhA dehydrogenates H-1 of 26 to form the heptadiene 28. Comparing the active centers, only three amino acid residues differ between AusE and PrhA: L150(AusE)/V150(PrhA), S232(AusE)/A232(PrhA), and V241(AusE)/M241(PrhA). By swapping these

• preandiloid C (58), and generates a radical leading to the construction of the bicyclo[2.2.2]octane skeleton of andiconin (59) (Figure 8) [36][37]. Two amino acid pairs, M119/N121 and A228/A230, in its substrate-binding pocket were mutated by saturation mutagenesis using degenerate primers, resulting in an

A new analog of dihydroxybenzoic acid from Saccharopolyspora sp. KR21-0001

• Rattiya Janthanom,
• Yuta Kikuchi,
• Hiroki Kanto,
• Tomoyasu Hirose,
• Arisu Tahara,
• Takahiro Ishii,
• Arinthip Thamchaipenet and
• Yuki Inahashi

Beilstein J. Org. Chem. 2024, 20, 497–503, doi:10.3762/bjoc.20.44

• HCl. The obtained amino acid (alanine) and authentic amino acids were modified using Nα-(5-fluoro-2,4-dinitrophenyl)-ᴅ-leucinamide (ᴅ-FDLA). The LC–MS analysis of ᴅ-FDLA derivatives revealed that the chiral center of the amino acid in 1 had ʟ configuration (Figure S7, Supporting Information File 1

Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells

• Fumihiro Ishikawa,
• Sho Konno,
• Hideaki Kakeya and
• Genzoh Tanabe

Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39

• arm in an adjacent peptidyl carrier protein (PCP). The amino acid loaded on the PCP then undergoes coupling with the amino acid loaded on the downstream PCP in the condensation (C) domain. Finally, the linear peptide on the PCP in the last module is either hydrolyzed or cyclized by a thioesterase (TE

• activities against the A-domain of MbtA, a component of mycobactin synthetase and antimicrobial activities against M. tuberculosis [7]. In addition, aminoacyl (AA)-AMS has been designed to inhibit the amino acid-activating A-domains in NRPSs and has been found to be a tight-binding inhibitor (Figure 2b) [8

• probes (AA-AMS-BPyne) can selectively label the A-domains corresponding to the amino acid of the ligand in both recombinant enzymes and proteomes. We recently reported that these probes can be used to label the A-domains of endogenous NRPSs in live bacterial cells [17][18][19]. The intracellular labeling

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

• 2 was determined by Marfey’s method. A biosynthetic gene cluster (BGC) encoding unguisins B and J was compared to characterized BGCs in other Aspergillus sp. Since the unguisin family of heptapetides incorporate different amino acid residues at different positions of the peptide, the A and C domains

• heptapeptides isolated predominantly from Aspergillus sp. [1][2][3][4][5][6][7][8]. Distinctive features of these cyclic peptides include the non-proteinogenic amino acid γ-aminobutyric acid (GABA) and the incorporation of up to five ᴅ-amino acids (Figure 1) [1][2][3][4][5][6][7][8]. The amino acids at

• , 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

Catalytic multi-step domino and one-pot reactions

• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25

• . Zhang, Ma, and W. Zhang reflects the state of the art in the α-amino acid-based [3 + 2] cycloaddition reactions of N–H-type azomethine ylides in multicomponent, one-pot, and stepwise reactions for the synthesis of diverse bioactive heterocyclic compounds and natural products [9]. Computational studies

Optimizations of lipid II synthesis: an essential glycolipid precursor in bacterial cell wall synthesis and a validated antibiotic target

• Milandip Karak,
• Cian R. Cloonan,
• Brad R. Baker,
• Rachel V. K. Cochrane and
• Stephen A. Cochrane

Beilstein J. Org. Chem. 2024, 20, 220–227, doi:10.3762/bjoc.20.22

• mixture which were then purified to give the desired α-anomers. Thioglycosides 1c, 1d, and 1f were isolated purely as β-anomers due to anchimeric assistance from the C2 N-acetyl or N-Troc groups. In glycosyl acceptors, the first amino acid of the lipid II pentapeptide, Ala, was incorporated as a 2

Copper-catalyzed multicomponent reaction of β-trifluoromethyl β-diazo esters enabling the synthesis of β-trifluoromethyl N,N-diacyl-β-amino esters

• Youlong Du,
• Haibo Mei,
• Ata Makarem,
• Ramin Javahershenas,
• Vadim A. Soloshonok and
• Jianlin Han

Beilstein J. Org. Chem. 2024, 20, 212–219, doi:10.3762/bjoc.20.21

• over 50% of agricultural chemicals contain at least one fluorine atom, among which architectural motifs containing fluorine and amino acid residues are a fast-growing segment of modern pharmaceuticals [10][11][12][13]. Fluoroalkyldiazo compounds belong to the most versatile and valuable reagents in

• example, Wan and co-workers developed a cascade reaction of α-diazo esters, nitriles, and carboxylic acids via the generation of nitrile ylides and Mumm rearrangement affording unsymmetric diacyl α-amino acid esters as products (Scheme 1a) [39]. In 2017, Zhang, Hu, and co-workers developed a Cu-catalyzed

Identification of the p-coumaric acid biosynthetic gene cluster in Kutzneria albida: insights into the diazotization-dependent deamination pathway

• Seiji Kawai,
• Akito Yamada,
• Yohei Katsuyama and
• Yasuo Ohnishi

Beilstein J. Org. Chem. 2024, 20, 1–11, doi:10.3762/bjoc.20.1

• ) [13]. CmaA2 and CmaA3 showed relatively high amino acid sequence similarity to AvaA2 and AvaA3, respectively (≈50% identity; see Table S2 in Supporting Information File 1). In contrast, low similarities were observed between CmaA2 and AvaA3, and between CmaA3 and AvaA2 (Table S2, Supporting

• CmaA2 and CmaA3 for CmaA1) is a matter of interest. The fact that AvaA1 and CmaA1 recognized CmaA3 and AvaA3, respectively, as partner ACP suggests that there are some important residues conserved between AvaA3 and CmaA3 for the ligase–ACP interaction. Indeed, two amino acid residues (Trp38 and His41 of

Decarboxylative 1,3-dipolar cycloaddition of amino acids for the synthesis of heterocyclic compounds

• Xiaofeng Zhang,
• Xiaoming Ma and
• Wei Zhang

Beilstein J. Org. Chem. 2023, 19, 1677–1693, doi:10.3762/bjoc.19.123

• with arylaldehydes are much less explored. The [3 + 2] adducts of α-amino acids could be used for a second [3 + 2] cycloaddition as well as for other post-condensation modifications. This article highlights our recent work on the development of α-amino acid-based [3 + 2] cycloaddition reactions of N–H

• stereoselectivity which limits the synthetic utility of non-stabilized AMYs of type C. There are over 300 papers on the amino acid-based decarboxylative [3 + 2] cycloadditions of N–R-type AMYs B1 (such as that derived from proline) and B2 [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49

• aldehydes and alkenes. The first cycloaddition products 3c or 3d can also be used as intermediates for other transformations to synthesize novel heterocyclic rings via multicomponent, one-pot, and stepwise synthesis [63][64]. Presented in the following sections is our work on the development of amino acid

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

• complexes, the fragment originating from the porphyrinoid could form hydrogen bonds with a carboxyl group, while the crown ether cavity would allow interaction with the protonated amine group of an amino acid molecule. The choice of macrocycle size could enable the recognition of different biomolecules

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• amino acid sequence of mfp-1, mfp-3, and mfp-5 (Y: DOPA, K: lysine). B) Scheme showing examples of the adhesive and cohesive properties of catechol-containing proteins. R represents the remainder of the mfp’s. Scheme 3 redrawn from [10]. Activation–deactivation equilibrium in nitroxide-mediated

Functions of enzyme domains in 2-methylisoborneol biosynthesis and enzymatic synthesis of non-natural analogs

• Binbin Gu,
• Lin-Fu Liang and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1452–1459, doi:10.3762/bjoc.19.104

• diphosphate synthase (FPPS) and 2MIBS from Streptomyces coelicolor [26] (Scheme 1B). Crystal structures of both enzymes have been obtained [27][28] and allowed for a deep structure-based investigation of 2MIBS through site-directed mutagenesis [29]. The predicted amino acid sequences of 2MIBS homologs from

• alignment with the short 2MIBS from Longispora albida DSM 44784 (WP_018349754) the border between domains A and B in the 2MIBS from S. coelicolor was identified. Domain A spans the amino acid residues 1–115 and domain B includes the amino acid residues 115–440. The gene sequences for both domains were

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• . Trapping of this enolate would lead to β-amino acid units, a class of compounds that has attracted a great deal of attention [19][20][21][22][23][24]. An obvious possible shortcoming that had to be considered was still that the generated zinc enolate III having a β-amino group could undergo β-elimination

• . Importantly, the protocol was found to be similarly applicable with enoates 8b (Table 3, entry 6) and 8c (entry 7) having tert-butyl and benzyl ester groups, which, as the methyl ester unit, are typical in the context of amino acid synthesis. ZnBu2 was also amenable to 1,4-addition (Table 3, entry 8), but not

•  5). Product (RS)-14b (85:15 dr), i.e., a mixture of two enantiomerically pure diastereomers, was obtained from (RS)-tert-butylsulfinamide upon allylation with tert-butyl α-(bromomethyl)acrylate followed by 1,4-addition with Et2Zn. It was then converted into the known β2-amino acid 17 by TFA-promoted

Functional characterisation of twelve terpene synthases from actinobacteria

• Anuj K. Chhalodia,
• Houchao Xu,
• Georges B. Tabekoueng,
• Binbin Gu,
• Kizerbo A. Taizoumbe,
• Lukas Lauterbach and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2023, 19, 1386–1398, doi:10.3762/bjoc.19.100

• synthase homologs from diverse actinobacteria that were selected based on a phylogenetic analysis of more than 4000 amino acid sequences were investigated for their products. For four enzymes with functions not previously reported from bacterial terpene synthases the products were isolated and their

• , Supporting Information File 1). The closest characterised terpene synthase with an amino acid sequence identity of 25% is the (1(10)E,4E,6S,7R)-germacradien-6-ol synthase from Streptomyces pratensis [33]. The recombinant enzyme efficiently converted FPP into one sesquiterpene alcohol whose electron

• . brevicatena (Table 1, entry 5) showed the highly conserved motifs with a modified aspartate-rich region (86DDHRN) and the NSE triad 227NDLHSMPKE (Figure S33, Supporting Information File 1). This enzyme is closely related to the epi-isozizaene synthase from S. coelicolor (EIZS) [24], but is with an amino acid

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

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• as H-bond donor to the catalyst (see transition state 97, Scheme 22a) [51]. Recently, the same research group documented another aza-Friedel–Crafts reaction between indoles 4 and 95 that frames aza-quaternary stereocenter at the α-carbon of unnatural amino acid derivatives 96. Enantiocontrol was

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• ). This reaction has been successfully used for common amines using acetic acid and water, but benzylamines and benzamides show no reaction under aqueous conditions. In the case of amino acid ester hydrochlorides, the reaction to give pyrrole can be carried out without the need for the two-phase