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

• (GABA) at the N-terminus of the Lys pentamer peptide on resin. Using the optimal reaction conditions, three types of hydrophilic peptide pentamers on resin, oligo-Lys (2a), oligo-Glu (2b), and oligo-Arg (2c), were subjected to the reaction with 3 for the synthesis of C60–peptide conjugates 5a–c (Figure

• on resin, a GABA residue was attached to the N-terminus of the peptide in order to provide a less-hindered primary amine, enabling an efficient amide conjugation reaction with biscarboxylic acid-substituted C60 derivative 3. Compound 3 was prepared by Prato reaction of C60 and an N-glycine derivative

• a similar peptide (GABA-(Lys)5-peptide-PEG) on resin for the reaction with compound 3. Initial trials, using 2-(1H-7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HATU) and N-methylmorpholine (NMM), respectively, as a coupling reagent and a base, and 5 equiv of peptide on

Research progress on the pharmacological activity, biosynthetic pathways, and biosynthesis of crocins

• Zhongwei Hua,
• Nan Liu and
• Xiaohui Yan

Beilstein J. Org. Chem. 2024, 20, 741–752, doi:10.3762/bjoc.20.68

• and enhance the antiepileptic effect of diazepam. The mechanism of action involved γ-aminobutyric acid (GABA) [38][39][40]. The brain-derived neurotrophic factor (BDNF)–tropomyosin receptor kinase B (TrkB) pathway is closely associated with epilepsy. Crocin can increase the BDNF level in the cortex of

HPW-Catalyzed environmentally benign approach to imidazo[1,2-a]pyridines

• Luan A. Martinho and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2024, 20, 628–637, doi:10.3762/bjoc.20.55

•  1 [13] and include alpidem (anxiety disorders), minodronic acid (osteoporosis), miroprofen (non-steroidal anti-inflammatory drug, NSAID), necopidem (insomnia), olprinone (acute heart failure), saripidem (type A GABA receptor agonist), zolimidine (gastroesophageal reflux disease), and zolpidem

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

• de São Paulo, CP 780, CEP 13560-970, São Carlos, SP, Brazil 10.3762/bjoc.20.32 Abstract Several under-explored Aspergillus sp. produce intriguing heptapeptides containing a γ-aminobutyric acid (GABA) residue with as yet unknown biological functions. In this study, a new GABA-containing heptapeptide

• 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

• positions 1 (ᴅ-Ala) and 7 (GABA) are conserved but there is considerable variability at positions 2–6, including the incorporation of additional non-proteinogenic amino acids β-methylphenylalanine (βMePhe) and kynurenine (Kyn) [3][4]. So far, no significant biological activities have been reported for these

Cyanothioacetamides as a synthetic platform for the synthesis of aminopyrazole derivatives

• Valeriy O. Filimonov,
• Alexandra I. Topchiy,
• Vladimir G. Ilkin,
• Tetyana V. Beryozkina and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2023, 19, 1191–1197, doi:10.3762/bjoc.19.87

• molecules that attack and destroy lipids and protein membranes of weed cells [10]. Fipronil is an inhibitor of GABA receptors and affects the nervous system of insects as a broad-spectrum insecticide [11][12]. On the other hand, thioamides are an important class of organic compounds. 6-Thioguanine and

A new route for the synthesis of 1-deazaguanine and 1-deazahypoxanthine

• Raphael Bereiter,
• Marco Oberlechner and
• Ronald Micura

Beilstein J. Org. Chem. 2022, 18, 1617–1624, doi:10.3762/bjoc.18.172

• ]-pyrimidines) [7][8][9] have been in the center of attention and were found to be effective compounds for the inhibition of various molecular targets associated with dysfunction of the central nervous system (e.g., as GABA and serotonin receptor modulators, or as inhibitors of phosphodiesterase PDE10A

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• muscimol (I) and ibotenic acid (II) (Figure 1) have been isolated from several fungal species and are active on the γ-aminobutyric acid (GABA) and glutamate receptors of the central nervous system (CNS), respectively [8][9]. Various unnatural amino acids bearing a 1,2-oxazole moiety, such as

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• -disubstituted glutarates, and the type-IV Guareschi synthesis is used in the preparation of the conformationally constrained γ-aminobutyric acid (GABA) analogue gabapentin (2) [3], a blockbuster drug for the management of neuropathic pain also used for a range of off-label indications that includes hot flashes

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Effective microwave-assisted approach to 1,2,3-triazolobenzodiazepinones via tandem Ugi reaction/catalyst-free intramolecular azide–alkyne cycloaddition

• Maryna O. Mazur,
• Oleksii S. Zhelavskyi,
• Eugene M. Zviagin,
• Svitlana V. Shishkina,
• Vladimir I. Musatov,
• Maksim A. Kolosov,
• Elena H. Shvets,
• Anna Yu. Andryushchenko and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2021, 17, 678–687, doi:10.3762/bjoc.17.57

• of 1,2,4-triazolobenzodiazepines is the treatment of central nervous system (CNS) disorders. Such drugs as alprazolam and estazolam are used as anxiolytic agents, whereas adinazolam is known as an antidepressant [3]. Benzodiazepine molecules are ligands for GABA-receptors and act as positive

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• antitumor [27][28][29][30], antifungal [31][32] or GABA receptor antagonist activity [33]. The most common synthesis of a given functionalized P-heterocyclic compound comprises the synthesis of the heterocyclic core, followed by its functionalization [27][29][34][35]. This latter step is of special

Synthesis of non-racemic 4-nitro-2-sulfonylbutan-1-ones via Ni(II)-catalyzed asymmetric Michael reaction of β-ketosulfones

• Alexander N. Reznikov,
• Anastasiya E. Sibiryakova,
• Marat R. Baimuratov,
• Eugene V. Golovin,
• Victor B. Rybakov and
• Yuri N. Klimochkin

Beilstein J. Org. Chem. 2019, 15, 1289–1297, doi:10.3762/bjoc.15.127

• ) complexes as catalyst for the Michael addition of 1,3-dicarbonyl compounds to nitroalkenes [47][48][49][50][51][52][53][54]. This reaction was used as a key stage in the synthesis of non-racemic analogues of GABA and substituted pyrrolidinones with neurotropic activity [47][51][52][54]. It should be noted

Synthesis of functionalised β-keto amides by aminoacylation/domino fragmentation of β-enamino amides

• Pavel Yanev and
• Plamen Angelov

Beilstein J. Org. Chem. 2018, 14, 2602–2606, doi:10.3762/bjoc.14.238

• -ketoamides 11 The longer chain in compounds 4 precludes the favourable 5-exo-trig process discussed earlier (Scheme 3) and accordingly there was no competing formation of cyclic side products. A different type of unwanted cyclisation occurred with the GABA derivatives 4b,c,f,j (n = 2) but here the competing

• present in the CDCl3 solutions of all β-keto amides 5 and 11. Along with that, the 1H NMR spectra of the GABA-derivatives 11b,c,f,j (n = 2) in CDCl3 indicated a ring–chain tautomeric equilibrium with 55–75% share of the open chain form. Although an estimation of the tautomeric ratio was possible through a

Semi-synthesis and insecticidal activity of spinetoram J and its D-forosamine replacement analogues

• Kai Zhang,
• Jiarong Li,
• Honglin Liu,
• Haiyou Wang and
• Lamusi A

Beilstein J. Org. Chem. 2018, 14, 2321–2330, doi:10.3762/bjoc.14.207

• spinosyn molecule interacts with both gamma-aminobutyric acid (GABA) receptor and nicotine acetylcholine (NACh) receptors [9]. Spinosad and spinetoram can be degraded via a combination of photolysis and microbial action, ultimately producing CO2, H2O, and nitrogen oxides [10]. That suggests that along with

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• protected naturally occurring amines such as GABA and phenylethylamine as well as diamines with orthogonal protecting groups, cf. product 2c. The combination of this protocol with the diastereoselective reductive amination reported by Hughes and Devine [41], provides access to very high value chiral α

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• examples of such clinically drugs having enhanced effects on the neurotransmitter γ-aminobutyric acid (GABA) at the GABAA receptor and low toxicity (Figure 1) [15]. Although 1,4-benzodiazepines are widely prescribed medicines, side effects like drowsiness, drug resistance, addiction and withdrawal

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• response element (ARE) and the estrogen response element (ERE) was synthesized in 12–17% overall yield. Selective modifications could also be done on the GABA turn units, which showed improved cellular uptake properties. Sugiyama et al. designed and synthesized a series of telomere-targeting synthetically

Investigations towards the stereoselective organocatalyzed Michael addition of dimethyl malonate to a racemic nitroalkene: possible route to the 4-methylpregabalin core structure

• Denisa Vargová,
• Rastislav Baran and
• Radovan Šebesta

Beilstein J. Org. Chem. 2018, 14, 553–559, doi:10.3762/bjoc.14.42

• amino acids have also been investigated as treatments for ocular disorders [7]. However, the syntheses of this type of compounds were long and relied on the use of Evans chiral auxiliaries or chiral starting materials. Various GABA derivatives were synthesized using asymmetric organocatalysis

• numerous Michael additions, as well as other reactions [11][12][13][14]. In this way, chiral thioureas, and squaramides were used to synthesize various GABA derivatives [15][16][17][18][19]. Interestingly, hydrogen-bonding activation of this kind of Michael additions worked well also in aqueous media [20

• ][21]. Other green chemistry concepts such as reusable media [22], immobilized catalysts [23], or flow set-ups have also been used with success for the synthesis of GABA derivatives [24]. Pregabalin is currently manufactured using enzymatic kinetic resolution [25], but an organocatalytic procedure

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

• Lingjun Xu,
• Shuwen Han,
• Linjie Yan,
• Haifeng Wang,
• Haihui Peng and
• Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

• pharmaceuticals, such as γ-aminobutyric acid (GABA) and γ-amino-β-hydroxybutyric acid (GABOB) analogues (baclofen HCl and pregabalin) [51][52][53][54], HMG-CoA reductase inhibitors (“statins”) [55][56][57], etc. The generality and scope of this methodology was further demonstrated in the alcoholysis of 8a with

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• formation inhibitors, GABA and benzodiazepine receptor agonists, and cardiotonic agents [7][8][9][10]. Further, the biological activities of imidazo[1,2-a]pyridines proved to be strongly depending upon the nature of substituents at C2 and C3 positions. For instance, the 3-aroylimidazo[1,2-a]pyridines 1c

Automating multistep flow synthesis: approach and challenges in integrating chemistry, machines and logic

• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2017, 13, 960–987, doi:10.3762/bjoc.13.97

Expression, purification and structural analysis of functional GABA transporter 1 using the baculovirus expression system

• Jing Hu,
• Chris Weise,
• Christoph Böttcher,
• Hua Fan and
• Jian Yin

Beilstein J. Org. Chem. 2017, 13, 874–882, doi:10.3762/bjoc.13.88

• Avenue1800, Wuxi 214122, China 10.3762/bjoc.13.88 Abstract The γ-aminobutyric acid (GABA) transporter 1 (GAT1) belongs to a family of Na+ and Cl−-coupled transport proteins and possesses 12 putative transmembrane domains. To perform structural analyses of the GAT1 protein, the GAT1/green fluorescent protein

• isolated in its monomeric form. Keywords: baculovirus expression system; chromatography; γ-aminobutyric acid (GABA); GABA transporter 1 (GAT1); Introduction γ-Aminobutyric acid (GABA) is the most abundant inhibitory neurotransmitter in the central nervous system (CNS) of vertebrate species. GABAergic

• neurotransmission is efficiently terminated through the quick removal of GABA from the synaptic cleft by GABA transporters (GATs). The activities of GATs are important for controlling the concentration and dwell time of GABA in the synaptic cleft and tightly regulating the synaptic inhibition of the GABA receptor

Contribution of microreactor technology and flow chemistry to the development of green and sustainable synthesis

• Flavio Fanelli,
• Giovanna Parisi,
• Leonardo Degennaro and
• Renzo Luisi

Beilstein J. Org. Chem. 2017, 13, 520–542, doi:10.3762/bjoc.13.51

• isolation of intermediates, separation of the catalyst or other work-up procedures can be considered sustainable [91]. The syntheses of (S)-rolipram and a γ-aminobutyric acid (GABA) derivative were accomplished. Readily available starting materials and columns containing chiral heterogeneous catalysts to

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• [29]. The corresponding amide 6 is a direct precursor of the GABA receptor agonist Baclofen (Scheme 5). Nitro compound 5 was continuously reduced in a 5 mL reactor and, after work-up under neutral conditions, chiral lactam 6 was isolated in 48% yield. Finally we explored the possibility of performing

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• -substituted esters 14a,b (λmax range from 319 to 325 nm) are substantially red-shifted relative to the pHP ester 4a (λmax at 287 nm) and exhibit molar extinction coefficients (ε) of ca. 104 M−1cm−1 in aq MeCN (Figure 2). For the 2,6-HNA DEP (10) and 2,6-HNA GABA, the λmax appears at 325 nm whereas the λmax

• for the 5,8-BQA phosphate 24 occurs at 321 nm in 10% aq MeCN. For the 2,6-HNA series, a strong fluorescence emission is observed at 470 nm as shown here for the more aqueous soluble GABA ester derivative. The 2,6-HNA GABA had better aqueous solubility for fluorescence studies. (See Supporting

• overall conversion to released substrate. The formation of competing chromophoric byproducts limits the conversion and yields [6][10][11][15]. For example, changing the leaving group for 10, i.e., photolysis of 6-hydroxy-2-naphthylacetyl GABA ester (Figure 2B) inefficiently released 4-aminobutyrate (GABA