Syntheses of spliceostatins and thailanstatins: a review

• William A. Donaldson

Beilstein J. Org. Chem. 2020, 16, 1991–2006, doi:10.3762/bjoc.16.166

• with their complex structure, a number of total syntheses have been reported. This review will compare the synthetic strategies reported through the end of 2019. Keywords: antiproliferative; polyketide natural products; tetrahydropyrans; total synthesis; Introduction The spliceostatins/thailanstatins

• (Figure 1) are a family of linear peptide/polyketide natural products isolated from the bacteria Burkholderia sp. FERM BP-3421 [1][2][3] (originally identified as Pseudomonas sp. No 2663) and Burkholderia sp. MSMB 43 [4][5]. These compounds are of interest due to their ability to bind to a subunit of the

Fabclavine diversity in Xenorhabdus bacteria

• Sebastian L. Wenski,
• Harun Cimen,
• Natalie Berghaus,
• Sebastian W. Fuchs,
• Selcuk Hazir and
• Helge B. Bode

Beilstein J. Org. Chem. 2020, 16, 956–965, doi:10.3762/bjoc.16.84

• ), and polyketide synthases (PKS). Selected Xenorhabdus and Photorhabdus mutant strains were generated applying a chemically inducible promoter in front of the suggested fabclavine (fcl) biosynthesis gene cluster (BGC), followed by the analysis of the occurring fabclavines. Subsequently, known and

• ]. Fabclavines are hexapeptide/polyketide hybrids derived from nonribosomal peptide synthetases (NRPS) and a polyketide synthase (PKS), which are connected to an unusual polyamine derived from polyunsaturated fatty acid (PUFA) synthases [20]. Beside full-length fabclavines, also shortened derivatives were

• (Ala) and the sixth position (R2/R3) between proline (Pro), valine (Val) and threonine (Thr). The polyamine can differ in the length from three to five amine units (m) and is connected via one to three partially reduced polyketide C2 units (n) with the NRPS part. In this work, 22 yet unknown

Two new aromatic polyketides from a sponge-derived Fusarium

• Mada Triandala Sibero,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Ocky K. Karna Radjasa,
• Agus Sabdono,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2019, 15, 2941–2947, doi:10.3762/bjoc.15.289

• polyketide; Fusarium; marine fungus; secondary metabolite; sponge; Introduction Marine organisms have been known as a potential source of prospective bioactive compounds, and sponges are particularly emphasized as the most promising source among all marine invertebrates [1][2]. However, the collection of

Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

• David C. B. Siebert,
• Roman Sommer,
• Domen Pogorevc,
• Michael Hoffmann,
• Silke C. Wenzel,
• Rolf Müller and
• Alexander Titz

Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

• . aeruginosa [18]. Biotechnological engineering of producer strains aims to shutdown the natural substrate production and thereby increase the usually poor yields of the mutasynthesis products [19][20]. For bacterial natural products that originate from a polyketide synthase (PKS) or a nonribosomal peptide

• are quite challenging, e.g., as shown in previous studies on polyketide chain engineering in α-pyrone antibiotic biosynthesis [23]. We assumed that the insufficient/missing processing of the SNAc precursors by the NRPS subunit Arg3 is the main culprit for unsuccessful restoration of the argyrin

Bacterial terpene biosynthesis: challenges and opportunities for pathway engineering

• Eric J. N. Helfrich,
• Geng-Min Lin,
• Christopher A. Voigt and
• Jon Clardy

Beilstein J. Org. Chem. 2019, 15, 2889–2906, doi:10.3762/bjoc.15.283

• thiotemplated assembly lines, such as type I polyketide synthases (PKS) and nonribosomal peptide synthetases (NRPS), are modular, with each module contributing a distinct fragment to the final product’s core structure – a short-chain carboxylic acid (PKS) or an amino acid (NRPS). The modularly defined template

• thiotemplate biosynthetic pathways that enable relatively precise predictions of natural product core structures (e.g., the colinearity rule in NRPSs and cis-acyltransferase polyketide synthases [8]), no such rules exist for the predictions of the cyclic hydrocarbon backbone produced by TCs [1]. This is likely

• assist in refining our understanding of bacterial terpenoid biosynthesis. Examples of bioactive terpenoids. Repetitive electrophilic and nucleophilic functionalities in terpene and type II PKS-derived polyketide biosynthesis. a) Schematic representation. b) Type II PKS-derived polyketide biosynthesis. c

Nanangenines: drimane sesquiterpenoids as the dominant metabolite cohort of a novel Australian fungus, Aspergillus nanangensis

• Heather J. Lacey,
• Cameron L. M. Gilchrist,
• Andrew Crombie,
• John A. Kalaitzis,
• Daniel Vuong,
• Peter J. Rutledge,
• Peter Turner,
• John I. Pitt,
• Ernest Lacey,
• Yit-Heng Chooi and
• Andrew M. Piggott

Beilstein J. Org. Chem. 2019, 15, 2631–2643, doi:10.3762/bjoc.15.256

• ], triterpenoids [10] and prenylated polyketide meroterpenoids [11][12][13][14][15] isolated from soil, endophytes and marine strains. Of this genus, A. ustus [16], A. calidoustus [17], A. insuetus [17], A. insulicola [18], A. bridgeri [18], A. sclerotiorum [19], A. variecolor [19], A. parasiticus [20], A. oryzae

• side chains present in the (iso)nanangenines could be derived either from a fatty acid synthase (FAS) or polyketide synthase (PKS). For example, in aflatoxin biosynthesis, the hexanoyl started unit is supplied by a FAS [31], while in the meroterpenoid fumagillin biosynthesis, the unsaturated acyl chain

Isolation and biosynthesis of an unsaturated fatty acid with unusual methylation pattern from a coral-associated bacterium Microbulbifer sp.

• Amit Raj Sharma,
• Enjuro Harunari,
• Tao Zhou,
• Agus Trianto and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2019, 15, 2327–2332, doi:10.3762/bjoc.15.225

• corroborated by 3JHH vicinal coupling constant (JH4,H5 = 15.8 Hz). In fungi and certain kinds of bacteria, methyl substituents in the fatty acid carbon chain or the polyketide chain are derived from the methyl group of S-adenosylmethionine (SAM) (Figure 3A) [13][14]. This methylation reaction usually occurs at

• the nucleophilic carbons originated from the methyl carbon of acetate (C2) since SAM acts as an electrophilic methyl donor. In most of the bacteria including actinomycetes, methyl branching in polyketide chain is derived from methylmalonyl CoA, thereby the methylation position must be also the α

• intermediate, from which deprotonation occurs at C9 to give an internal olefin (Scheme 1). In the case of 1, methylation at the C3 carbon is inconsistent with the regular methylation pattern that occurs in fatty acids synthesized by the FAS (fatty acid synthase) or polyketides from the PKS (polyketide synthase

Synthesis of the polyketide section of seragamide A and related cyclodepsipeptides via Negishi cross coupling

• Jan Hendrik Lang and
• Thomas Lindel

Beilstein J. Org. Chem. 2019, 15, 577–583, doi:10.3762/bjoc.15.53

• Jan Hendrik Lang Thomas Lindel TU Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106 Braunschweig, Germany 10.3762/bjoc.15.53 Abstract The synthesis of the polyketide section present in the potently cytotoxic marine cyclodepsipeptide jasplakinolide and related natural products

• endeavour, a new synthesis of the polyketide section present in seragamides and most of jasplakinolides and geodiamolides. We also include the synthesis of the protected tripeptide section of seragamide A (2), even if the macrocycle still remains to be assembled. Seragamide A (2) from the marine sponge

• Suberites japonicus (Thiele) has been synthesized only once, with relay ring-closing metathesis being the key step [9]. Characteristically, seragamides A–E exhibit a L-threonine unit at the C-terminus of the peptide moiety. There is a considerable body of work on the synthesis of the C12 polyketide section

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• pathogenic against humans, they are widely used as biocontrol agents in agriculture [9]. Natural products produced by bacteria play an important role in the bacteria/nematode/insect life cycle and most natural products are non-ribosomal peptides (NRP), e.g., rhabdopeptides [10][11] and polyketide–NRP hybrids

Volatiles from the hypoxylaceous fungi Hypoxylon griseobrunneum and Hypoxylon macrocarpum

• Jan Rinkel,
• Alexander Babczyk,
• Tao Wang,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 2974–2990, doi:10.3762/bjoc.14.277

• derivatives. Their structures could only be unambiguously determined by comparison to all isomers with different substitution patterns. The substitution pattern of the main compound from H. griseobrunneum, the new natural product 2,4,5-trimethylanisole, was explainable by a polyketide biosynthesis mechanism

• (methyl-2H3)methionine. While the methylation pattern of the alternative structure 24c is difficult to understand via a polyketide biosynthesis mechanism, the formation of the assigned structure of 24 by a polyketide synthase (PKS) can be easily rationalised (Scheme 2). The acetate starter unit, bound to

• exhibited the mass spectra shown in Figure 4E and Figure 4F that were similar to database spectra of 2,5-dimethyl-p-anisaldehyde (25) and methyl 2,5-dimethyl-p-anisate (26). The substitution pattern of these compounds is well explained by polyketide biosynthesis logic (Scheme 3). Starting from ACP-bound

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• chiral hypervalent iodine catalyst [47][48]. Additionally, mCPBA and trifluoroacetic acid were utilized as terminal oxidants and activators, respectively. This reaction provided a series of 4-oxyisochroman-1-ones, which are found in natural products and bioactive polyketide metabolites. For example, the

Volatiles from the tropical ascomycete Daldinia clavata (Hypoxylaceae, Xylariales)

• Tao Wang,
• Kathrin I. Mohr,
• Marc Stadler and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2018, 14, 135–147, doi:10.3762/bjoc.14.9

• is shown in Scheme 7 that is likely performed by a typical fungal iterative polyketide synthase (PKS). Starting from acyl-carrier-protein (ACP) bound acetate a first elongation step with malonyl-SCoA (Mal-SCoA) catalysed by an acyl transferase (AT) and a ketosynthase (KS) domain yields acetoacetyl

Herpetopanone, a diterpene from Herpetosiphon aurantiacus discovered by isotope labeling

• Xinli Pan,
• Nicole Domin,
• Sebastian Schieferdecker,
• Hirokazu Kage,
• Martin Roth and
• Markus Nett

Beilstein J. Org. Chem. 2017, 13, 2458–2465, doi:10.3762/bjoc.13.242

• . Although the elemental composition does not necessarily exclude a polyketide origin, it perfectly matches a diterpene comprising four intact isoprene units. To obtain sufficient material for structure elucidation, the fermentation of H. aurantiacus 114-95T was repeated on a 50 L scale in VNY medium

Sulfation and amidinohydrolysis in the biosynthesis of giant linear polyenes

• Hui Hong,
• Markiyan Samborskyy,
• Katsiaryna Usachova,
• Katharina Schnatz and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2017, 13, 2408–2415, doi:10.3762/bjoc.13.238

• from Streptomyces mediocidicus), are near-identical giant linear polyenes apparently constructed from, respectively, a 4-guanidinobutanoate or 4-aminobutanoate starter unit and 27 polyketide extender units, and bearing a specific O-sulfonate modification at the C-29 hydroxy group. We show here that

• as donor, efficiently converted mediomycin B to mediomycin A in vitro. Thus, in the final steps of mediomycin A biosynthesis deamidination and sulfotransfer can take place in either order. Keywords: amidinohydrolase; clethramycin; mediomycin; polyketide synthase; sulfotransferase; Introduction

• Bacterial modular polyketide synthases (PKSs) follow an assembly-line paradigm for enzyme catalysis, in which each round of chain extension requires a different set, or module, of enzymatic activities [1][2][3][4]. Among the more remarkable natural products derived by this pathway is the giant linear

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

• , based on studies investigating the stability of M. ulcerans extracts towards different chemicals and enzymes [31]. The true nature of the toxin, however, remained elusive until 1998, when Small and co-workers identified a polyketide isolated from acetone-soluble M. ulcerans lipid extracts as the key

• activity. Further purification of this material by reversed-phase HPLC and subsequent characterization by high-resolution mass spectrometry and two-dimensional NMR spectroscopy unveiled a 12-membered macrolactone substituted with two polyketide-derived side chains (Figure 1). Based on its mycobacterial

• origin and its chemical structure, this compound was named mycolactone. It is worth noting that mycolactone represented the first polyketide macrolide isolated from a mycobacterial species and was also the first example of a polyketide acting as the virulence factor of a human pathogen [34]. The purified

Strategies in megasynthase engineering – fatty acid synthases (FAS) as model proteins

• Manuel Fischer and
• Martin Grininger

Beilstein J. Org. Chem. 2017, 13, 1204–1211, doi:10.3762/bjoc.13.119

• Megasynthases are large multienzyme proteins that produce a plethora of important natural compounds by catalyzing the successive condensation and modification of precursor units. Within the class of megasynthases, polyketide synthases (PKS) are responsible for the production of a large spectrum of bioactive

• engineering strategies in the light of the newly emerging structural information on megasynthases, and argue that fatty acid synthases (FAS) are and will be valuable objects for further developing this field. Keywords: fatty acid synthases; megasynthases; metabolic enzyme engineering; polyketide synthases

• antineoplastic doxorubicin and by the antiparasitic avermectin (Figure 1a) [1]. PK are assembled from acyl-coenzyme A (acyl-CoA) units via a series of Claisen-type condensation reactions catalyzed by polyketide synthases (PKS) (Figure 1b). PKS occur as large multifunctional enzymes, termed megasynthases, which

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• the archazolids, complex polyketide macrolides which present the most potent V-ATPase inhibitors known to date, rendering these macrolides important lead structures for the development of novel anticancer agents. The limited natural supply of these metabolites from their myxobacterial source renders

• of these multimeric enzymes also in cancer development and progression was discovered and has been increasingly unraveled. The archazolids, polyketide macrolides from the myxobacterium Archangium gephyra, have played a key role in these studies. They present the most potent V-ATPase inhibitors known

• full stereochemistry in the first place. The various approaches discussed within this manuscript show the various tactics and strategies that may be employed in complex polyketide synthesis. Notable features of the total synthesis by the Menche group include the robustness of boron mediated aldol

Lipids: fatty acids and derivatives, polyketides and isoprenoids

• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2017, 13, 793–794, doi:10.3762/bjoc.13.78

• biosynthetically related polyketide pathways, and terpenoid biosynthesis. I hope that the present Thematic Series of the Beilstein Journal of Organic Chemistry on the interdisciplinary topic of “Lipids” will cover many topics of high interest to readers from chemistry, biochemistry, biophysics, medicine, pharmacy

Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces

• Enjuro Harunari,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47

• , Kisarazu, Chiba 292-0818, Japan 10.3762/bjoc.13.47 Abstract Butyrolactol A is an antifungal polyketide of Streptomyces bearing an uncommon tert-butyl starter unit and a polyol system in which eight hydroxy/acyloxy carbons are contiguously connected. Except for its congener butyrolactol B, there exist no

• valine and its C-methylation with methionine and the polyol carbons are derived from a glycolysis intermediate, possibly hydroxymalonyl-ACP. Keywords: biosynthesis; butyrolactol; contiguous polyol; hydroxymalonyl-ACP; polyketide; Streptomyces; tert-butyl; Introduction Actinomycetes produce structurally

• /carbohydrate/nucleic acid derivatives [1][2]. One of the largest groups of bacterial secondary metabolites is polyketide from which a range of clinically used drugs have been developed. Polyketides still remain in the focus of drug development because of their structural complexity that can provide attractive

Polyketide stereocontrol: a study in chemical biology

• Kira J. Weissman

Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39

• biosynthesis of reduced polyketides in bacteria by modular polyketide synthases (PKSs) proceeds with exquisite stereocontrol. As the stereochemistry is intimately linked to the strong bioactivity of these molecules, the origins of stereochemical control are of significant interest in attempts to create

• this approach to provide answers to fundamental biological questions. Keywords: chemical biology; polyketide synthases; reduced polyketides; stereocontrol; Introduction Reduced polyketides and their derivatives form the basis for a number of medicines in current clinical usage, notably anti

• functionality in a defined way in three dimensions, allowing them to bind their biological targets with useful affinity (10−7 to 10−9 M [4]). Erythromycin A (1, Figure 1) is the prototypical polyketide, as its biosynthesis has been studied most heavily to date. The structure incorporates 10 stereocenters, and

A non-canonical peptide synthetase adenylates 3-methyl-2-oxovaleric acid for auriculamide biosynthesis

• Daniel Braga,
• Dirk Hoffmeister and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 2766–2770, doi:10.3762/bjoc.12.274

• microorganism as a promising source of natural products. Genes for nonribosomal peptide synthetases (NRPSs) were found to be preponderant, either solely or organised in combination with polyketide synthase (PKS) genes, representing four and five clusters, respectively. Two PKS and three putative bacteriocin

Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase

• Hui Hong,
• Yuhui Sun,
• Yongjun Zhou,
• Emily Stephens,
• Markiyan Samborskyy and
• Peter F. Leadlay

Beilstein J. Org. Chem. 2016, 12, 2164–2172, doi:10.3762/bjoc.12.206

• , and Wuhan University School of Pharmaceutical Sciences, Wuhan 430071, People’s Republic of China 10.3762/bjoc.12.206 Abstract The assembly-line synthases that produce bacterial polyketide natural products follow a modular paradigm in which each round of chain extension is catalysed by a different set

• (marginolactones) azalomycin and kanchanamycin, isolated respectively from Streptomyces malaysiensis DSM4137 and Streptomyces olivaceus Tü4018, the first extension module catalyses both the first and second cycles of polyketide chain extension. To confirm the integrity of the azl gene cluster, it was cloned intact

• produced azalomycin, showing that the polyketide synthase genes in the sequenced cluster are sufficient to accomplish formation of the full-length polyketide chain. This provides strong support for module iteration in the azalomycin and kanchanamycin biosynthetic pathways. In contrast, re-sequencing of the

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• of the present review is to assemble key results of these applications and illustrate scope and limitations. Review Oxidative cyclizations in the synthesis of carbohydrates, amino acids and polyketide natural products (+)-Anhydro-D-glucitol and (+)-D-chitaric acid (+)-Anhydro-D-glucitol (6) was

• of this polyketide. At this point it has to be mentioned that in 1987 the group of Weiler also used such a permanganate-promoted oxidative cyclization for the stereoselective synthesis of the THF unit in ionomycin [63]. Similarly, in 1980 Walba et al. reported on the B/C-ring fragment synthesis of

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• Bayreuth, Germany 10.3762/bjoc.12.148 Abstract This review highlights the biosynthesis of heterocycles in polyketide natural products with a focus on oxygen and nitrogen-containing heterocycles with ring sizes between 3 and 6 atoms. Heterocycles are abundant structural elements of natural products from

• ]. Polyketides Polyketide natural products are biosynthesised by polyketide synthases (PKSs) of the types I–III. Type I PKS are multimodular megaenzyme complexes that produce linear, reduced polyketides in an assembly line process that uses acyl carrier proteins (ACP), ketosynthase (KS) and acyl transferase (AT

• their standard catalytic repertoire (Scheme 1). They transacylate the thioester of a PKS-bound polyketide onto a nucleophile. If the nucleophile is water, this leads to carboxylic acids. The reactions of backbone hydroxy groups or amines consequently give lactones and lactams. TE domains mostly form

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• annotation software, which means that some putative RiPP precursors are not even listed in databases. Furthermore, novel classes are difficult to identify precisely due to their novelty compared to known pathways. This is in contrast to terpenes, polyketide synthases or NRPSs, whose pathways are all clearly