Allostreptopyrroles A–E, β-alkylpyrrole derivatives from an actinomycete Allostreptomyces sp. RD068384

• Marwa Elsbaey,
• Naoya Oku,
• Mohamed S. A. Abdel-Mottaleb and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2024, 20, 1981–1987, doi:10.3762/bjoc.20.174

• many marine natural products [6][7], pyrroles substituted with long hydrocarbon chains (pyrrole lipids) are seldomly isolated, and their presence is limited to certain marine organisms [8]. A series of 3-alkylpyrrole-2-carbaldehydes/carboxylic acid/methylcarboxylate was reported from the marine sponge

• Oscarella lobularis (Figure 1 and Figure S54 in Supporting Information File 1) [7][9], but the actual position of the alkyl chains is very likely to be on the 5 position, as Stierle and Faulkner pointed in their study on a series of 5-alkylpyrrole-2-carbaldehydes from the sponge Laxosuberites sp. [10]. From

• and carboxyl functionalities. Furthermore, a β-alkyl substitution is not very common in pyrrolic secondary metabolites. The most related metabolites to 1–5 are the reported alkylpyrroles from a marine sponge Oscarella lobularis [7] and pyrroloterpenes from Streptomyces [12][13][14][15], although the

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

• dimethylated [81][123]. Polytheonamides are originally derived from the marine sponge Theonella swinhoei, which is colonised by various symbiotic bacteria. The polytheonamide encoding BGC poy includes two B12-dependent rSAM C-MTs, namely PoyB and PoyC. In silico modelling and alignment of the structures of

Polymer degrading marine Microbulbifer bacteria: an un(der)utilized source of chemical and biocatalytic novelty

• Weimao Zhong and
• Vinayak Agarwal

Beilstein J. Org. Chem. 2024, 20, 1635–1651, doi:10.3762/bjoc.20.146

• –12 against Staphlyococcus aureus indicated that 7 and 12 were bacteriostatic, while 9 and 10 were bactericidal. Compound 9 was also active towards another two commensal Gram-positive bacteria Bacillus sp. and Planococcus sp. isolated from the host sponge. Compound 9 can be detected in situ in the

• sponge collected at different times, suggesting it may serve an ecological role in the balance between bacterial community and the sponge host [13]. Jayanetti et al. investigated 16 Microbulbifer strains isolated from marine tunicate Ecteinascidia turbinate. Among these, one strain Microbulbifer sp. WMMC

• a sponge-derived Microbulbifer strain [73]. This deep purple pigment has been isolated from several other bacterial genera [129], including but not limited to the epiphytic commensal marine bacteria of the genus Pseudoalteromonas where the biosynthetic pathway was eventually established [130][131

A Diels–Alder probe for discovery of natural products containing furan moieties

• Alyssa S. Eggly,
• Namuunzul Otgontseren,
• Carson B. Roberts,
• Amir Y. Alwali,
• Haylie E. Hennigan and
• Elizabeth I. Parkinson

Beilstein J. Org. Chem. 2024, 20, 1001–1010, doi:10.3762/bjoc.20.88

• isolated from a sea sponge, Plakortis simplex [3][4]. Wortmannin, which also has a furan, was isolated from Penicillium wortmannin and shows anticancer activity via potent inhibition of phosphoinositide 3-kinase [5]. These are just a handful of the bioactive natural products containing furans that exist

Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

• Ekaterina V. Kolupaeva,
• Narek A. Dzhangiryan,
• Alexander F. Pozharskii,
• Oleg P. Demidov and
• Valery A. Ozeryanskii

Beilstein J. Org. Chem. 2024, 20, 243–253, doi:10.3762/bjoc.20.24

• , Pushkin str. 1a, 355017 Stavropol, Russian Federation 10.3762/bjoc.20.24 Abstract The possibility of functionalization of dipyrido[3,2-e:2′,3′-h]acenaphthene containing a quino[7,8-h]quinoline fragment and being a highly basic diazine analog of 1,8-bis(dimethylamino)naphthalene (“proton sponge”) has been

• forced to strongly repel each other in space, can lead to a sharp increase in basicity [8]. Thus, quino[7,8-h]quinoline (3), first obtained in the Staab group [9], already exceeds in basicity not only quinoline itself, but also 1,8-bis(dimethylamino)naphthalene (1, “proton sponge”) (Scheme 1; pKa values

• % yield directly from diamine 4 [15]. This result is contrary to the initial report [16]. Compound 5 still has the properties of a rather strong heterocyclic base, having higher basicity than “proton sponge” (Scheme 1) [15]. Although the physicochemical properties of acenaphthene 5, including structure

Synthesis of 7-azabicyclo[4.3.1]decane ring systems from tricarbonyl(tropone)iron via intramolecular Heck reactions

• Aaron H. Shoemaker,
• Elizabeth A. Foker,
• Elena P. Uttaro,
• Sarah K. Beitel and
• Daniel R. Griffith

Beilstein J. Org. Chem. 2023, 19, 1615–1619, doi:10.3762/bjoc.19.118

• , entry 2) and Vanderwal [17] (Table 1, entry 3) in the synthesis of other bridged azapolycycles gave poor yields when applied to vinyl bromide 7. The best result was obtained using the combination of Pd(PPh3)4, K2CO3, and proton sponge in refluxing toluene [18][19]. Although this catalyst system proved

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• , which exploit the carbon-rich nature, porous framework, and expanded π-electron system of these compounds [11]. And this is not a complete list. Recently, we reported on the synthesis of 1,4-diaryl-1,3-butadiynes 1–4 based on the “proton sponge” [1,8-bis(dimethylamino)naphthalene, DMAN] (Figure 1) [15

• ]. In the present work we describe the synthesis of a new family of proton sponge-based butadiynes 5 bearing arylethynyl substituents of different electronic nature. Oligomers 5 having electron-withdrawing groups on the aryl termini are interesting as push–pull A–π–D–π–D–π–A systems, whereas the

• counterpart with an electron-donating methoxy group can be converted into a D–π–A–π–A–π–D system by protonation of the proton sponge fragments (Figure 2). Moreover, oligomers 5 are cross-conjugated π-systems. “A cross-conjugated compound may be defined as a compound possessing three unsaturated groups, two 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

• Indonesian sponge Haliclona sp. [108]. Their synthesis takes advantage of the same tandem procedure that gives β-ketoester 219. The asymmetric conjugate 1,4-addition and subsequent acylation provided good stereocontrol and the authors could revise the thus far incorrectly assigned configuration of the target

Sequential hydrozirconation/Pd-catalyzed cross coupling of acyl chlorides towards conjugated (2E,4E)-dienones

• Benedikt Kolb,
• Daniela Silva dos Santos,
• Sanja Krause,
• Anna Zens and
• Sabine Laschat

Beilstein J. Org. Chem. 2023, 19, 176–185, doi:10.3762/bjoc.19.17

• from a haliclona marine sponge [4], and vertinolide (5) from Verticillium intertextum [5] (Scheme 1). As outlined in Scheme 2, a variety of methods has been reported for the synthesis of conjugated dienones, mostly via addition/elimination reactions such as Knoevenagel condensation or Claisen–Schmidt

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• 2021) [37]: Dysideanone B (75), isolated from the South China Sea sponge Dysidea avara, possesses an unprecedented 6/6/6/6-fused tetracycle with interesting anticancer properties against HeLa and HepG2 cancer cell lines (Scheme 6) [38]. The structurally similar dysiherbols 79 and 80, bearing a 6/6/5/6

Synthesis of (−)-halichonic acid and (−)-halichonic acid B

• Keith P. Reber and
• Emma L. Niner

Beilstein J. Org. Chem. 2022, 18, 1629–1635, doi:10.3762/bjoc.18.174

• aminobisabolene sesquiterpenoid halichonic acid ((+)-1) from the sponge Halichondra sp. (Figure 1) [4]. This amino acid natural product features a rigid 3-azabicyclo[3.3.1]nonane ring system containing four stereogenic centers within the piperidine ring. In 2021, the same group re-isolated (+)-1 from the sponge

• [7], we viewed the halichonic acids as ideal targets to extend the scope of our synthetic methodology. Given the structural similarity between compounds (+)-1 and (+)-2 (and the fact that they were co-isolated from the same sponge), Tsukamoto et al. proposed that these natural products could be

• , antifungal, and antimicrobial properties [10][19][20][21][22]. Notably, (+)-4 was also co-isolated with compounds (+)-1 and (+)-2 in sponge extracts, suggesting that these compounds may share a common biosynthetic pathway [4][5]. Both enantiomers of 4 have been previously synthesized [9][23][24], and this

Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library

• Sasha Hayes,
• Aya C. Taki,
• Kah Yean Lum,
• Joseph J. Byrne,
• Merrick G. Ekins,
• Robin B. Gasser and
• Rohan A. Davis

Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164

• , 3010, Australia Biodiversity and Geosciences, Queensland Museum, Grey Street, Brisbane, 4101, Australia 10.3762/bjoc.18.164 Abstract In order to further expand the NatureBank open access compound library, chemical investigations of the Australian marine sponge, Ianthella basta, were undertaken since

• UHPLC–MS analysis of the extract from this sponge indicated the presence of a new alkaloid. Large-scale extraction and mass-directed isolation studies on the CH2Cl2/MeOH I. basta extract resulted in the purification of a new bromotyrosine-derived alkaloid, 5-debromopurealidin H (1), along with the known

• (6), hexadellin A (9) and bastadin 4 (5) showed inhibition towards larval motility after 72 h of exposure with IC50 values of 1.6 µM, 10.0 µM and 33.3 µM, respectively. Keywords: alkaloid; anthelmintic; biodiscovery; bromotyrosine; 5-debromopurealidin H; Ianthella; NatureBank; sponge; Introduction

Vicinal ketoesters – key intermediates in the total synthesis of natural products

• Marc Paul Beller and
• Ulrich Koert

Beilstein J. Org. Chem. 2022, 18, 1236–1248, doi:10.3762/bjoc.18.129

• Palau’amine (45), a dimeric pyrrole-imidazole-bisguanidine alkaloid, was first isolated from the marine sponge Stylotella aurantium in 1993 [16][17]. It received considerable attention from the synthetic community because of its broad range of biological activities and complex structure. In an early endeavour

Anti-inflammatory aromadendrane- and cadinane-type sesquiterpenoids from the South China Sea sponge Acanthella cavernosa

• Shou-Mao Shen,
• Qing Yang,
• Yi Zang,
• Jia Li,
• Xueting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 916–925, doi:10.3762/bjoc.18.91

• , namely (+)-maninsigin D [(+)-4], (+)- and (−)-ximaocavernosin Q [(+)- and (−)-5], together with five related known ones [2, 3, (−)-4, 6, and 7], were isolated from the Hainan sponge Acanthella cavernosa. Compounds 4 and 5 were isolated as racemic forms, which were further separated to the corresponding

• anti-inflammatory activity by the inhibition of LPS-induced TNF-α and CCL2 release in RAW 264.7 macrophages. Keywords: Acanthella cavernosa; anti-inflammatory; biosynthetic pathway; chiral separation; marine sponge; sesquiterpenoid; Introduction Marine sponges of the genus Acanthella (class

• diterpenes [7][8], alkaloids [9], and steroids [10], have been isolated and characterized. In connection with our continuing studies of Chinese marine invertebrates to search for novel and bioactive secondary metabolites, we have recently studied the sponge A. cavernosa collected from Ximao Island of Hainan

Four bioactive new steroids from the soft coral Lobophytum pauciflorum collected in South China Sea

• Di Zhang,
• Zhe Wang,
• Xiao Han,
• Xiao-Lei Li,
• Zhong-Yu Lu,
• Bei-Bei Dou,
• Wen-Ze Zhang,
• Xu-Li Tang,
• Ping-Lin Li and
• Guo-Qiang Li

Beilstein J. Org. Chem. 2022, 18, 374–380, doi:10.3762/bjoc.18.42

• Supporting Information File 62: Crystal data and structure refinement for compounds 1–3 and NMR, MS, and IR spectra of compounds 1–4. Acknowledgements Special thanks are given to Dr. Pingjyun Sung (National Museum of Marine Biology and Aquarium (NMMBA), Checheng, Pingtung 944, Taiwan, China), for the sponge

Cryogels: recent applications in 3D-bioprinting, injectable cryogels, drug delivery, and wound healing

• Luke O. Jones,
• Leah Williams,
• Tasmin Boam,
• Martin Kalmet,
• Chidubem Oguike and
• Fiona L. Hatton

Beilstein J. Org. Chem. 2021, 17, 2553–2569, doi:10.3762/bjoc.17.171

• , gelatin sponge, gauze, and QCSG/CNT0 [116]. Cryogels comprising the natural biopolymers silk fibroin and chitosan, with tannic acid and ferric ions (Fe3+) incorporated have been reported as multifunctional devices for wound healing providing hemostasis, exudate absorbance, antibacterial effects, and

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

• White’s oxidation method as the final step in the first total synthesis of gracilioether F (75) [157], a natural polyketide with an unusual tricyclic core and five contiguous stereocenters, part of the family of gracilioethers 71–74 (Scheme 26A) extracted from the marine sponge Plakinastrella mamillaris

• action of Meerwein’s salt (Me3OBF4) and a mild base (proton sponge) to afford a methoxy cedrene derivative. Next, oxidative cleavage of the double bond using NaIO4/RuCl3·xH2O enabled a ring opening, followed by lactonization promoted by CuBr2 via an intramolecular acyloxylation. The 5,5-fused ring system

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• shown promising biological activities in preclinical and clinical studies (Figure 1) [2][3][4][5][6]. The pyrimidine-γ-carboline alkaloid ingenine B (isolated from an Indonesian sponge) exhibits a pronounced cytotoxicity against a murine lymphoma cell line [7] and several isocanthine analogs are

Structural effects of meso-halogenation on porphyrins

• Keith J. Flanagan,
• Maximilian Paradiz Dominguez,
• Zoi Melissari,
• Hans-Georg Eckhardt,
• René M. Williams,
• Dáire Gibbons,
• Caroline Prior,
• Gemma M. Locke,
• Alina Meindl,
• Aoife A. Ryan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2021, 17, 1149–1170, doi:10.3762/bjoc.17.88

• few decades. Byrn et al. were the first to observe that porphyrins have a high propensity to form “porous” clathrates and suggested that they can be used as a “porphyrin sponge” [1]. They reported that 5,10,15,20-tetraphenylporphyrin could act like a ‘host’ which could trap a variety of solvent

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

• Joseane A. Mendes,
• Paulo R. R. Costa,
• Miguel Yus,
• Francisco Foubelo and
• Camilla D. Buarque

Beilstein J. Org. Chem. 2021, 17, 1096–1140, doi:10.3762/bjoc.17.86

• alkaloids that were isolated in the mid-1990s from the Caribbean sponge bataella sp. From a biological point of view, the batzelladines have received attention due to their reported activity as inhibitors of HIV gp120-human CD4 binding. Chiral N-tert-butanesulfinyl aldimine (SS)-58 was used as a precursor

Identification of volatiles from six marine Celeribacter strains

• Anuj Kumar Chhalodia,
• Jan Rinkel,
• Dorota Konvalinkova,
• Jörn Petersen and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2021, 17, 420–430, doi:10.3762/bjoc.17.38

• marine organisms, e.g., Thalassococcus halodurans DSM 26915T has been isolated from the marine sponge Halichondria panicea [5], and Phaeobacter gallaeciensis DSM 26640T is an isolate from the scallop Pecten maximus [6]. Important interactions are also observed between bacteria from the roseobacter group

The preparation and properties of 1,1-difluorocyclopropane derivatives

• Kymbat S. Adekenova,
• Peter B. Wyatt and
• Sergazy M. Adekenov

Beilstein J. Org. Chem. 2021, 17, 245–272, doi:10.3762/bjoc.17.25

• isomerization [36]. Several nitrogen nucleophiles have been evaluated as catalysts to promote the difluorocarbene formation from TFDA in order to bring about the cyclopropanation of a 2-siloxybuta-1,3-diene derivative; 1,8-bis(dimethylamino)naphthalene (proton sponge) was found to be particularly effective [37

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• last, carbazole-based heterohelicenes were found in nature, for example, purpurone [55] isolated from the marine sponge Iotrochota sp. and having an inhibitory effect on the ATP-citrate lyase, and the marine alkaloid ningalin D produced by Didemnum sp., Dictyodendrins [56] isolated from Dictyodendrilla

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• but provides a new insight into the structural/biosynthetic diversity in microbial secondary metabolites. Finally, it should be noted that the R-enantiomer-rich anteisoalkyl group is extremely rare: only two ceramides, each from the dinoflagellate Coolia monotis [33] and the sponge Ephydatia syriaca

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• an endosomal pathway. The low pKa value of the four GCP moieties could result in an improved buffering capacity, which could facilitate endosomal escape by the proton-sponge effect [28]. Significant inhibition of DNA transfection by bafilomycin (a macrolide antibiotic that can block the endosomal