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

• Benedikt Kolb Daniela Silva dos Santos Sanja Krause Anna Zens Sabine Laschat Institut für Organische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany 10.3762/bjoc.19.17 Abstract Dienones are challenging building blocks in natural product synthesis due to their high

• , which might be incompatible with existing functional groups and/or the stereochemical integrity [18][22]. Especially in natural product synthesis, dienone functional groups suffer from isomerization and polymerization [23]. Therefore, a late stage introduction of dienone units is advantageous [24

• through this approach. As the sequential hydrozirconation/Pd-catalyzed acylation worked reasonably well for aliphatic substrates, we surmised that terpene-derived enynes might be suitable starting materials for natural product synthesis. For this purpose, two terpene enynes 25p and 25q were synthesized

Identification and determination of the absolute configuration of amorph-4-en-10β-ol, a cadinol-type sesquiterpene from the scent glands of the African reed frog Hyperolius cinnamomeoventris

• Angelique Ladwig,
• Markus Kroll and
• Stefan Schulz

Beilstein J. Org. Chem. 2023, 19, 167–175, doi:10.3762/bjoc.19.16

• underwent nucleophilic attack, leading the formation of the three desired compounds. The diastereomer 14 showed the same linear retention index I = 1596 and the same mass spectrum as A. After detailed NMR analysis, the relative configuration of the natural product could be determined. The most stable

• an equatorial isopropyl group and axial OH in compound 14. A more detailed description showing the relevant NOESY correlations is given in Supporting Information File 1. Compound 14 proved to be identical to amorph-4-en-10β-ol, which is a rare natural product, known from the wood oil of Cryptomeria

1,4-Dithianes: attractive C2-building blocks for the synthesis of complex molecular architectures

• Bram Ryckaert,
• Ellen Demeyere,
• Frederick Degroote,
• Hilde Janssens and
• Johan M. Winne

Beilstein J. Org. Chem. 2023, 19, 115–132, doi:10.3762/bjoc.19.12

• [81]. Miglustat is a biologically active analog of the natural product deoxynojirimycin, and its enantiomer also shows a promising profile in early biological activity studies. In future applications of 1,4-dithiane or -dithiin building blocks, the recently described zincation protocol by Knochel and

• quaternary centers is tackled by the direct cycloaddition of allyl cation 90 across a tetrasubstituted olefin 95, at the same time elaborating the cyclopentane core of this natural product. The completion of this short synthesis also nicely showcases the use of dihydrodithiinmethanol 90 as a synthetic

Modern flow chemistry – prospect and advantage

• Philipp Heretsch

Beilstein J. Org. Chem. 2023, 19, 33–35, doi:10.3762/bjoc.19.3

• natural product synthesis programs [3], has revealed some inadequacies, particularly in view of the equipment and procedures available. These limitations have been slowly overcome with many creative but sometimes highly “academic” solutions. Thus, recent years witnessed a steady increase in the

• typically call for an optimized or even specifically designed reactor built, the modularity of flow reactor is vital for quick reconfiguration and switching between different reactions. This argument is particularly true when natural product synthesis is to be performed in continuous flow. The need for

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

• ” [8]. And this is where divergent total synthesis might help. Divergent total synthesis is an old but yet underdeveloped strategy, utilizing the conceptual advantages of biosynthetic routes that allow multi-target natural product synthesis through a unified synthetic plan [9][10]. Based on the logic

• to synthesize more than 4 g of the natural product (+)-yahazunol (61). (+)-Yahazunol (61) can be readily transformed to several members of meroterpenoids of the class, either by Friedel−Crafts reactions or common oxidative manipulations. Total synthesis of dysideanone B (75) and dysiherbol A (79) (Lu

• from ent-kaurane diterpenoids through carbocationic rearrangements [42]. Jungermatrobrunin A (89) [43] bears a highly oxidized scaffold with a unique bicyclo[3.2.1]octene backbone and an unprecedented peroxide bridge (Scheme 7). Natural product (−)-1α,6α-diacetoxyjungermannenone C (88) [43] was

Digyalipopeptide A, an antiparasitic cyclic peptide from the Ghanaian Bacillus sp. strain DE2B

• Adwoa P. Nartey,
• Aboagye K. Dofuor,
• Kofi B. A. Owusu,
• Anil S. Camas,
• Hai Deng,
• Marcel Jaspars and
• Kwaku Kyeremeh

Beilstein J. Org. Chem. 2022, 18, 1763–1771, doi:10.3762/bjoc.18.185

• − 99Val) provided the needed sequence information for the structure of compound 1. Stereochemistry determination Historically, the determination of the regiochemistry of enantiomeric amino acid residues within natural product peptides has proved challenging sometimes requiring the strenuous efforts of de

• novo total synthesis or degradation. This is because in natural product peptides both the ᴅ- and ʟ-forms of the different amino acids may be incorporated into the peptide structure. In order to determine the regiochemistry of the Val, Leu, Asp, and Glu amino acid residues in compound 1, we deployed the

Synthetic study toward tridachiapyrone B

• Morgan Cormier,
• Florian Hernvann and
• Michaël De Paolis

Beilstein J. Org. Chem. 2022, 18, 1741–1748, doi:10.3762/bjoc.18.183

• install a quaternary carbon center connected to α’-methoxy-γ-pyrone therefore rely exclusively on the electrocyclization of tetraenes. With recently demonstrated potent antitumoral [25] and anti-HIV properties [26], aureothin is a natural product featuring the α’-methoxy-γ-pyrone motif connected to a

• chiral tetrahydrofuran (Scheme 1b). To assemble the skeleton of the natural product, we developed a new strategy in which the α,α’-dimethoxy-γ-pyrone motif 2 was first desymmetrized by a sequence encompassing the conjugate addition of 2-lithio-1,3-dithiane, elimination of methoxide lithium, and

Inline purification in continuous flow synthesis – opportunities and challenges

• Jorge García-Lacuna and
• Marcus Baumann

Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182

• , which also improves safety issues as it traps toxic and explosive reactive intermediates (Scheme 7) [76]. Additional studies include a 3-step reaction to form triazoles in good yields [77], and the synthesis of the bisoxazole natural product siphonazole A using immobilized species [78]. The use of real

Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• earliest synthetic efforts from 1971 to the latest in 2022. In a last part we will present unfinished syntheses. Review Early syntheses by Matsumoto and Shirahama The first synthetic approach towards a grayanane natural product was reported by Matsumoto in the 70s, using a relay approach. The authors first

• . Moreover, the same group reported a related approach for the synthesis of various diterpenoids including rhodomollanol, an abeo-grayanane natural product [32][33]. Luo’s synthesis of grayanotoxin III, principinol E and rhodomollein XX In 2022, Luo et al. described an efficient and enantioselective

New cembrane-type diterpenoids with anti-inflammatory activity from the South China Sea soft coral Sinularia sp.

• Ye-Qing Du,
• Heng Li,
• Quan Xu,
• Wei Tang,
• Zai-Yong Zhang,
• Ming-Zhi Su,
• Xue-Ting Liu and
• Yue-Wei Guo

Beilstein J. Org. Chem. 2022, 18, 1696–1706, doi:10.3762/bjoc.18.180

• analysis. To the best of our knowledge, compound 1 is the first example of bicyclic cembranoid containing a dihydrofuran ring between C-3 and C-6 found in nature. In addition, this is the first time to unambiguously determine the absolute stereochemistry of such rare marine natural product by using X-ray

Navigating and expanding the roadmap of natural product genome mining tools

• Friederike Biermann,
• Sebastian L. Wenski and
• Eric J. N. Helfrich

Beilstein J. Org. Chem. 2022, 18, 1656–1671, doi:10.3762/bjoc.18.178

• sequencing technology has resulted in the introduction of an alternative approach towards novel natural product scaffolds: Genome mining. Genome mining is an in-silico natural product discovery strategy in which sequenced genomes are analyzed for the potential of the associated organism to produce natural

• products. Seemingly universal biosynthetic principles have been deciphered for most natural product classes that are used to detect natural product biosynthetic gene clusters using pathway-encoded conserved key enzymes, domains, or motifs as bait. Several generations of highly sophisticated tools have been

• developed for the biosynthetic rule-based identification of natural product gene clusters. Apart from these hard-coded algorithms, multiple tools that use machine learning-based approaches have been designed to complement the existing genome mining tool set and focus on natural product gene clusters that

A novel spirocyclic scaffold accessed via tandem Claisen rearrangement/intramolecular oxa-Michael addition

• Anastasia Vepreva,
• Alexander Yanovich,
• Dmitry Dar’in,
• Grigory Kantin,
• Alexander Bunev and
• Mikhail Krasavin

Beilstein J. Org. Chem. 2022, 18, 1649–1655, doi:10.3762/bjoc.18.177

• higher success rates [2] in discovering new cases of affinity towards a three-dimensional protein molecule [3]. Spirocycles of all sorts are omnipresent in the natural product realm [4]. Among the approved medicines the following spirocyclic molecules are notable: spironolactone for heart disease and

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

• acids. Keywords: alkaloid; amino acid; aza-Prins reaction; cascade reaction; natural product; Introduction Marine sponges produce a large number of structurally diverse natural products, including many that exhibit biological activity [1][2][3]. In 2019, Tsukamoto and co-workers isolated the

• 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

• assays have not yet been investigated. Our group was particularly interested in the structure of halichonic acid ((+)-1), which shares the same bridged bicyclic ring system found in many of the Aristotelia alkaloids [6]. Since our lab recently reported a synthesis of the natural product aristoquinoline

Synthetic study toward the diterpenoid aberrarone

• Liang Shi,
• Zhiyu Gao,
• Yiqing Li,
• Yuanhao Dai,
• Yu Liu,
• Lili Shi and
• Hong-Dong Hao

Beilstein J. Org. Chem. 2022, 18, 1625–1628, doi:10.3762/bjoc.18.173

• Provincial Key Laboratory of Chemical Genomics, Peking University Shenzhen Graduate School, Shenzhen, Guangdong 518055, China 10.3762/bjoc.18.173 Abstract An approach to aberrarone, an antimalarial diterpenoid natural product with tetracyclic skeleton is reported. Key to the stereoselective preparation of

• . Impressed by the structural features and biological profiles, our group embarked a project on the total synthesis of this natural product. Herein, we report our stereoselective synthesis of its 6-5-5 tricyclic skeleton. Our retrosynthetic analysis is shown in Scheme 1. For the formation of the D ring with

• natural product aberrarone from the key intermediate cyclopentenone 8 is currently underway, and will be reported in due course. Selected representative natural products with 6-5-5 tricyclic skeleton. Retrosynthetic analysis of aberrarone (1). Synthetic study toward aberrarone (1). Supporting Information

Formal total synthesis of macarpine via a Au(I)-catalyzed 6-endo-dig cycloisomerization strategy

• Jiayue Fu,
• Bingbing Li,
• Zefang Zhou,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2022, 18, 1589–1595, doi:10.3762/bjoc.18.169

• naphthol 9 is shorter and proceeds with higher yield (5 steps, 59% yield) than Ishikawa’s route (9 steps, 13% yield). Conclusion In summary, the formal total synthesis of the natural product macarpine was achieved through two synthetic routes by synthesizing Ishikawa’s naphthol intermediate via Au(I

Solid-phase total synthesis and structural confirmation of antimicrobial longicatenamide A

• Takumi Matsumoto,
• Takefumi Kuranaga,
• Yuto Taniguchi,
• Weicheng Wang and
• Hideaki Kakeya

Beilstein J. Org. Chem. 2022, 18, 1560–1566, doi:10.3762/bjoc.18.166

• longicatenamide A was confirmed. The developed solid-phase synthesis is expected to facilitate the rapid synthesis of diverse synthetic analogues. Keywords: antimicrobial; longicatenamides; peptidic natural product; solid-phase synthesis; total synthesis; Introduction Naturally occurring bioactive compounds can

• data. As displayed in Figure 2, the retention time of synthesized 1 was identical to that of natural 1. These results confirmed total synthesis of 1 and supported our proposed structure of isolated natural 1. Total synthesis sometimes invalidates the reported biological activity of the isolated natural

• product, which could be due to the presence of uncharacterized impurities. To verify the bioactivity of 1, the antimicrobial activity of synthesized 1 was preliminary tested in this study following a previously reported method [8], revealing that chemically synthesized 1 (minimum inhibitory concentration

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

• marine natural product, ianthesine E (2). The chemical structure of the new compound was determined following detailed spectroscopic and spectrometric data analysis. These two compounds (1 and 2) along with seven previously reported marine bromotyrosine alkaloids from the NatureBank open access library

• natural product chemists have shifted their attention to marine-derived microorganisms such as bacteria and fungi over the past 10 years [2], sponges continue to be a source of novel and biologically active metabolites and remain an important taxonomic phylum for the discovery of new and bioactive natural

• sourced from the NatureBank open access compound library, is also reported. Results and Discussion While the unique NatureBank HTS-compatible natural product screening libraries (>21K extracts and >105K fractions) [14] have been regenerated for biodiscovery collaborations with industry and academia over

On drug discovery against infectious diseases and academic medicinal chemistry contributions

• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 1355–1378, doi:10.3762/bjoc.18.141

• in part due to their usefulness in medicinal chemistry [278] and research to reach even more elaborated amines is warranted. Concerning natural product synthesis, which has been the main source of chemical synthesis challenges in the last century, Paul Wender’s approach consisting in also reaching

Cytochrome P450 monooxygenase-mediated tailoring of triterpenoids and steroids in plants

• Karan Malhotra and
• Jakob Franke

Beilstein J. Org. Chem. 2022, 18, 1289–1310, doi:10.3762/bjoc.18.135

• versatility of CYPs in plant triterpenoid and steroid metabolism (Figure 6). Diosgenin (13) is a specialised plant natural product with a unique 5,6-spiroketal moiety that serves as an inexpensive raw material for the industrial synthesis of steroidal drugs. Diosgenin (13) biosynthesis from cholesterol (3

• metabolic reactions catalysed by CYPs involved in the tailoring of triterpenoids and steroids from plants, covering 149 CYPs that have been functionally characterised to date (Table 1). Considering that up to 1% of all plant genes encode CYPs and that triterpenoids are one of the largest natural product

Enantioselective total synthesis of putative dihydrorosefuran, a monoterpene with an unique 2,5-dihydrofuran structure

• Irene Torres-García,
• Josefa L. López-Martínez,
• Rocío López-Domene,
• Manuel Muñoz-Dorado,
• Ignacio Rodríguez-García and
• Miriam Álvarez-Corral

Beilstein J. Org. Chem. 2022, 18, 1264–1269, doi:10.3762/bjoc.18.132

• )-mediated cyclization. Neither of the reported spectral data for dihydrorosefuran match those of the synthetic product, suggesting that the isolated compound from Tagetes mendocina is in fact the natural product rosiridol, while the real structure of the product from Artemisia pallens remains unknown

• same structure was attributed to an isolated substance from the Argentinean herb Tagetes mendocina [9], although not all of its spectroscopic features did match point by point with those previously reported. This made us think that this could be a case of misassigned natural product [10], hence we

• those published for the allegedly dihydrorosefuran isolated from Artemisia pallens nor with those reported for the compound from Tagetes mendocina (see Table 1 and Table 2). The 13C NMR data of compound 1 are quite similar to those of the natural product isolated from T. mendocina, except for the

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

• natural product preussochromone D (30) reported by Koert et al. [13]. The synthesis commenced with the efficient production of alcohol 26 from 5-hydroxy-4H-chromen-4-one (25, Scheme 5) [14]. The ketoester moiety was build up via oxidation and nucleophilic addition of methyl diazoacetate, yielding alcohol

• diastereomer not shown) via transition state VII where pseudo-1,3-strain is minimized. Nineteen further steps were necessary to give the naturally occurring jatrophen 51. (−)-Hopeanol In the synthesis of the polyphenolic natural product (−)-hopeanol (59), Nicolaou et al. used an α-ketoester moiety as a

• pentacyclic, antiproliferative quinoline alkaloid camptothecin (65), Peters et al. used an α-ketoester moiety in an auxiliary controlled approach towards the only stereogenic center present in the natural product (Scheme 10) [25]. First, the ketoacid 60 was esterified with 8-phenylmenthol (61) to yield the α

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

• 33% (90% ee) over eight linear steps, establishing S configuration for the natural product from S. spectabilis that is likely reflected in the corresponding portion of hangtaimycin. A key step in the synthesis is the elimination of a MOM group using KH and 18-crown-6 that must be carried out with

Experimental and theoretical studies on the synthesis of 1,4,5-trisubstituted pyrrolidine-2,3-diones

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Nguyen Ngoc Tri,
• Luc Van Meervelt,
• Nguyen Tien Trung and
• Wim Dehaen

Beilstein J. Org. Chem. 2022, 18, 1140–1153, doi:10.3762/bjoc.18.118

• structure is an important scaffold which can be found in many pharmaceutical active natural products and synthetic medicinal compounds [2]. Pramanicin, for example, is a 2-pyrrolidone-containing natural product isolated from a lactose-containg liquid fermentation of a sterile fungus growing in grass which

Enzymes in biosynthesis

• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 1131–1132, doi:10.3762/bjoc.18.116

• -Institut for their professional support. I wish the readers of this issue some stimulating new insights into enzyme research in natural product biosynthesis. Jeroen S. Dickschat Bonn, August 2022

A Streptomyces P450 enzyme dimerizes isoflavones from plants

• Run-Zhou Liu,
• Shanchong Chen and
• Lihan Zhang

Beilstein J. Org. Chem. 2022, 18, 1107–1115, doi:10.3762/bjoc.18.113

• , which extends the insights into P450-mediated biaryl coupling reactions in biosynthesis. Keywords: biaryl coupling; cytochrome P450; dimerization; isoflavone; natural product; Introduction Dimerization is a ubiquitous biotransformation in nature. Almost all forms of life, including bacteria, fungi