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

• step using milder conditions (Scheme 3). The newly developed synthesis started from 7 that was Boc-protected at the indole to yield 11. Removal of the benzyl group by catalytic hydrogenation to 12 was followed by coupling with benzyloxycarbonyl (Cbz) and methoxymethyl (MOM)-protected threonine to give

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

• broad peak corresponding to the proton of the secondary amino group (NH) at a chemical shift of 11.74 ppm. The intramolecular hydrogen bond led to the appearance of a resonance signal of the amino group at high chemical shift. Also, the coupling between the amino proton and methylene protons was

• observed. In addition, the methylene protons are diastereotopic and they show geminal coupling. As a consequence, the two methylene protons were observed as two doublets of doublets at 4.40 ppm and 4.49 ppm, respectively. Moreover, the HMBC 2D NMR spectrum of compound 10aa also exhibited the correlation

Heterogeneous metallaphotoredox catalysis in a continuous-flow packed-bed reactor

• Wei-Hsin Hsu,
• Susanne Reischauer,
• Peter H. Seeberger,
• Bartholomäus Pieber and
• Dario Cambié

Beilstein J. Org. Chem. 2022, 18, 1123–1130, doi:10.3762/bjoc.18.115

• (catalyst) separation in one step. The use of a packed bed simplifies the translation of optimized batch reaction conditions to continuous flow, as the only components present in the reaction mixture are the substrate and a base. The metallaphotoredox cross-coupling of sulfinates with aryl halides was used

• coupling between 4-iodobenzotrifluoride and sodium p-toluenesulfinate was chosen as the model reaction [28]. In contrast to other protocols, this reaction does not require any additives, such as a base, which allows for a straightforward proof-of-principle study on the long-term stability of the polymeric

• systematically study the cross-coupling using the packed-bed reactor, we decided to equip the continuous-flow setup with a dedicated tool for in-line analysis. Such techniques enable rapid investigations of process-related parameters [34]. In particular, the presence of a trifluoromethyl group in the substrate

Electrogenerated base-promoted cyclopropanation using alkyl 2-chloroacetates

• Kouichi Matsumoto,
• Yuta Hayashi,
• Kengo Hamasaki,
• Mizuki Matsuse,
• Hiyono Suzuki,
• Keiji Nishiwaki and
• Norihito Kawashita

Beilstein J. Org. Chem. 2022, 18, 1116–1122, doi:10.3762/bjoc.18.114

• (benzyltriethylammonium chloride) produced triethyl cyclopropane-1,2,3-tricarboxylate in 62% yield (Scheme 1, reaction 2) [11]. Both procedures are two-component coupling reactions. In contrast, a method involving a one-component reaction using alkyl 2-haloacetate has been developed by Abushanab in 1967, in which a

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

• dimers or cross-coupling products, starting from simple monomers [17][18][19]. Nevertheless, our knowledge of enzyme-mediated dimerization is still limited in contrast to the numerous reported dimeric natural products. Phenol coupling in plant polyphenol biosynthesis is one of the earliest documented

• and S4, Supporting Information File 1) suggested that 1 has a biaryl linkage between the two A-rings. The 1H,1H-COSY correlation of H-5’’ (δH 8.06, d) and H-6’’ (δH 7.03, d) revealed C-8’’ as one of the coupling sites. The methoxy group (δH 3.98, s) was assigned to the C-7 site because of the 1H,1H

Synthesis of N-phenyl- and N-thiazolyl-1H-indazoles by copper-catalyzed intramolecular N-arylation of ortho-chlorinated arylhydrazones

• Yara Cristina Marchioro Barbosa,
• Guilherme Caneppele Paveglio,
• Claudio Martin Pereira de Pereira,
• Sidnei Moura,
• Cristiane Storck Schwalm,
• Gleison Antonio Casagrande and
• Lucas Pizzuti

Beilstein J. Org. Chem. 2022, 18, 1079–1087, doi:10.3762/bjoc.18.110

• reaction of hydrazones and p-benzoquinones [16], and Co3+/Cu2+-catalyzed C−N/N−N coupling of imidates with anthranils as both aminating reagents and organic oxidants [17]. Additional established routes to 1H-indazoles comprise transition metal‐catalyzed [18][19][20] and metal-free [21][22] intramolecular

Electrochemical formal homocoupling of sec-alcohols

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masashi Shiota,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2022, 18, 1062–1069, doi:10.3762/bjoc.18.108

• Kosuke Yamamoto Kazuhisa Arita Masashi Shiota Masami Kuriyama Osamu Onomura Graduate School of Biomedical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan 10.3762/bjoc.18.108 Abstract Electrochemical pinacol coupling of carbonyl compounds in an undivided cell with a

• electrolysis; Introduction Carbon–carbon bond formation is one of the most fundamental and important reactions in synthetic organic chemistry. Reductive coupling of carbonyl compounds known as pinacol coupling would be a powerful method to construct vic-1,2-diol scaffolds through C–C bond formation [1][2

• ]. Such scaffolds are widely utilized as versatile building blocks in the synthesis of biologically active compounds [3][4][5][6][7], chiral auxiliaries [8][9], and chiral ligands [10][11][12][13]. Traditional pinacol coupling reactions are performed with a stoichiometric or even excess amount of low

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• with two (diphenylamino)carbazole-thiophene units as D (electron-donating group)–π (π-conjugated bridge) moiety and the (D–π)2Ph-type fluorescent dye OTK-2 with the two D–π moieties connected through a phenyl ring were derived by oxidative homocoupling of a stannyl D–π unit and Stille coupling of a

• orbital (MO) calculations. Results and Discussion Using a toluene solution containing 1,3-diiodobenzene and (diphenylamino)carbazole-thiophenestannane derivative 1 [33] in the presence of Pd(PPh3)4, the (D–π)2-type and (D–π)2Ph-type fluorescent dyes OTK-2 [33] and OTT-2 were obtained by Stille coupling of

Electrochemical Friedel–Crafts-type amidomethylation of arenes by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborate

• Hisanori Senboku,
• Mizuki Hayama and
• Hidetoshi Matsuno

Beilstein J. Org. Chem. 2022, 18, 1040–1046, doi:10.3762/bjoc.18.105

• plate cathode and a Pt wire anode (a quasi-divided cell) [24][25][26][27][28] in the presence of carbon dioxide resulted in reductive carboxylation at the cathode and selective formation of N-acyliminium ions of DMF at the anode to produce coupling products, N-phenylacetoxymethyl-N-methylformamides, in

• likely nucleophile in this reaction medium was the trifluoroacetate ion, which was produced by electrochemical reduction of TFA at the cathode, although we could not detect the coupling product of trifluoroacetate and the corresponding N-acyliminium ion due to the high solubility in water. In addition to

New azodyrecins identified by a genome mining-directed reactivity-based screening

• Atina Rizkiya Choirunnisa,
• Kuga Arima,
• Yo Abe,
• Noritaka Kagaya,
• Kei Kudo,
• Hikaru Suenaga,
• Junko Hashimoto,
• Manabu Fujie,
• Noriyuki Satoh,
• Kazuo Shin-ya,
• Kenichi Matsuda and
• Toshiyuki Wakimoto

Beilstein J. Org. Chem. 2022, 18, 1017–1025, doi:10.3762/bjoc.18.102

• nitrogen radical coupling mechanism in the biosynthesis of azoxymycins [12][13], which are aromatic azoxy natural products. A similar mechanism has been envisioned for the autoxidation and spontaneous dimerization of aliphatic hydroxylamines via the azoxy linkage in malleobactin D biosynthesis [14]. A

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

• halides are valuable compounds with potent bioactivities [1][2][3][4][5] (Figure 1) and are utilized as crucial precursors for various metal-catalyzed cross-coupling reactions [6][7][8][9]. They are frequently used as synthetic intermediates in several value-added syntheses of natural products

• of monoiodo derivatives was successfully prepared in high to excellent yields from phenols and anilines by adding 1.1 equiv of NIS with PEG-400 as the LAG agent (product 2aa–ag, Scheme 3). Notably, both Br- and I-substituents are mainly used as the substrates for cross-coupling reactions indicating

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• DPX400 (400 and 101 MHz, respectively) spectrometer. Chemical shifts are reported on the δ scale in ppm and were referenced to residual solvent (CDCl3: 7.27 ppm for 1H NMR spectra and 77.0 ppm for 13C NMR spectra). Coupling constants (J) were given in Hz and matched where possible. The following

Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

• Naoki Kise and
• Toshihiko Sakurai

Beilstein J. Org. Chem. 2022, 18, 956–962, doi:10.3762/bjoc.18.95

• Naoki Kise Toshihiko Sakurai Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori University, 4-101, Koyama-cho Minami, Tottori 680-8552, Japan 10.3762/bjoc.18.95 Abstract The electroreductive coupling of 2-acylbenzoates with acrylonitrile in the presence of TMSCl

• studied using DFT calculations. Keywords: 2-acylbenzoates; chlorotrimethylsilane; 3-(3-cyanoethyl)phthalides; 2-cyanonaphthalen-1-ols; electroductive coupling; Introduction The electroreductive coupling between carbon–heteroatom and carbon–carbon double bonds is one of the promising methods for carbon

• –carbon bond formation [1][2][3][4]. Recently, we reported the electroreductive coupling of phthalic anhydrides with α,β-unsaturated carbonyl compounds in the presence of chlorotrimethylsilane (TMSCl) and subsequent treatment with 1 M HCl to give 1,4-dihydroxynaphthalenes and 2-methyl-2,3

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• [34], dibromodithienothiophene 24 is lithiated with n-butyllithium at −90 °C, and the resulting species is reacted in situ with triisopropyl borate. After aqueous workup, dithieno[3,2-b:2’,3’-d]thiophene-2,6-diylboronic acid (25) is obtained, enabling subsequent Suzuki–Miyaura cross-coupling [36

• ]. This palladium-catalysed cross coupling is preferred over a Stille cross-coupling due to the high toxicity of organotin reagents [37]. Moreover, purification of compound 25 is facile since it can be used for further reactions after re-precipitation in petroleum ether. In a manner similar to [35], it is

• possible to convert 25 into the corresponding pinacol ester, 2,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)dithieno[3,2-b:2’,3’-d]thiophene (26) by stirring 25 with pinacol in refluxing toluene, but this has no beneficial impact on the subsequent cross-coupling. Compound 26 has been published

On Reuben G. Jones synthesis of 2-hydroxypyrazines

• Pierre Legrand and
• Yves L. Janin

Beilstein J. Org. Chem. 2022, 18, 935–943, doi:10.3762/bjoc.18.93

• , respectively. Shifts (δ) are given in ppm with respect to the TMS signal and cross-coupling constants (J) are given in hertz. Column chromatography was performed either on Merck silica gel 60 (0.035–0.070 mm) or neutral alumina containing 1.5% of added water using a solvent pump and an automated collecting

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

• solvent signals, and coupling constants (J) were in Hz. HRESIMS spectra were recorded on an Agilent G6520 Q-TOF mass spectrometer, while HREIMS spectra were recorded on a Finnigan-MAT-95 mass spectrometer (Thermo Fisher Scientific, Waltham, USA). Commercial silica gel (Qingdao Haiyang Chemical Group Co

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• -oxides 42 and 44 in moderate 54–63% yields via the intramolecular copper-catalyzed cross-coupling of ethyl/benzyl 2-bromobenzylphosphonamidates 41 or P-(2-bromobenzyl)-P-(methyl)phosphinamide (43) as a key step. They were prepared from 2-bromobenzyl bromide (38) via three and four steps, respectively

• method was more efficient than the DCC coupling one. The similar treatment of alkyl 2-aminobenzyl(phenyl)phosphinates 53 and 63 gave 1-alkyl-2-phenyl-1,3-dihydrobenzo[d][1,2]azaphosphole 2-oxides 56 in 51–65% yield through the alkyl transfer from the O to the N atom followed by dehydration under heating

• -phenylphosphonamidates 240a (R’ = OEt) and diaryl-N-phenylphosphinamides 240b–d (R’ = Ar), respectively, with methyl acrylate (241) via the rhodium-catalyzed oxidative coupling and subsequent intramolecular aza-Michael addition. Methyl acrylate (241) could be replaced by various electron-deficient olefins 244, including

Efficient production of clerodane and ent-kaurane diterpenes through truncated artificial pathways in Escherichia coli

• Fang-Ru Li,
• Xiaoxu Lin,
• Qian Yang,
• Ning-Hua Tan and
• Liao-Bin Dong

Beilstein J. Org. Chem. 2022, 18, 881–888, doi:10.3762/bjoc.18.89

• optimal combination of efflux pumps for ent-kaurene production [39], the titer was enhanced by 3.5-fold in this study. The strategy outlined here not only provides an efficient pathway to overproduce clerodane and ent-kaurane carbon skeletons but also offers a blueprint for coupling with emerging

Synthesis of novel alkynyl imidazopyridinyl selenides: copper-catalyzed tandem selenation of selenium with 2-arylimidazo[1,2-a]pyridines and terminal alkynes

• Mio Matsumura,
• Kaho Tsukada,
• Kiwa Sugimoto,
• Yuki Murata and
• Shuji Yasuike

Beilstein J. Org. Chem. 2022, 18, 863–871, doi:10.3762/bjoc.18.87

• selenides [25]. In this reaction, unlike the former, bis(imidazo[1,2-a]pyridin-3-yl) diselenides are generated through C–H selenation at the 3-position of 2-arylimidazopyridines with Se powder, followed by the cross-coupling reaction between diselenides and triarylbismuthines. These one-pot reactions are

• imidazopyridinyl selenides A Cu-catalyzed cross-coupling reaction using benzene ring substituted diaryl diselenides with terminal alkynes in the presence of bases is effective for synthesizing aryl alkynyl selenides [27][28][29][30][31]. We previously reported a simple method for the synthesis of bis(2-arylimidazo

• % yields (Table 2, entries 1–4). The electronic nature of the substituents in the arylalkynes 3 did not affect the outcome of the reaction. For terminal alkynes 3f and 3g with a heteroaryl group such as thiophene (Table 2, entry 5) and the vinyl group (Table 2, entry 6), the coupling products 4af and 4ag

Palladium-catalyzed solid-state borylation of aryl halides using mechanochemistry

• Koji Kubota,
• Emiru Baba,
• Tamae Seo,
• Tatsuo Ishiyama and
• Hajime Ito

Beilstein J. Org. Chem. 2022, 18, 855–862, doi:10.3762/bjoc.18.86

• , Japan 10.3762/bjoc.18.86 Abstract This study describes the solid-state palladium-catalyzed cross-coupling between aryl halides and bis(pinacolato)diboron using ball milling. The reactions were completed within 10 min for most aryl halides to afford a variety of synthetically useful arylboronates in

• mill; borylation; cross-coupling; mechanochemistry; solid-state reaction; Introduction Arylboronic acid and its derivatives are indispensable reagents in modern synthetic chemistry because they have been frequently used for the preparation of many bioactive molecules, natural products, and functional

• organic materials, typically through Suzuki–Miyaura coupling [1][2][3][4][5][6][7]. The palladium-catalyzed boryl substitution of aryl halides with boron reagents, termed Miyaura–Ishiyama borylation, is an efficient method for synthesizing arylboronates with high functional group compatibility [8][9][10

First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation

• Maxime Pypec,
• Laurent Jouffret,
• Claude Taillefumier and
• Olivier Roy

Beilstein J. Org. Chem. 2022, 18, 845–854, doi:10.3762/bjoc.18.85

• -(alkylamino)glycine units is investigated. We demonstrate that N-(methylamino)glycine homooligomers can be readily synthesized in solution using N-Boc-N-methylhydrazine as a peptoid submonomer and stepwise or segment coupling methodologies. Their structures were analyzed in solution by 1D and 2D NMR, in the

• substitution step, due to the close polarities of the products and starting hydrazine reagent. So we turned our attention to a fragment-based coupling approach for synthesizing the hexamer peptoid 6. Thus, several coupling methods were evaluated, initially starting from the hydrazine and acid monomers 1a and

• 1c, respectively (Scheme 2). The N-Fmoc-protected acid partner 1c was readily prepared from 1a under standard conditions. After a few unsuccessful attempts of coupling using the azabenzotriazole-based coupling reagent HATU [42] or via the formation of an acid chloride with thionyl chloride, we turned

Synthesis and HDAC inhibitory activity of pyrimidine-based hydroxamic acids

• Virginija Jakubkiene,
• Gabrielius Ernis Valiulis,
• Markus Schweipert,
• Asta Zubriene,
• Daumantas Matulis,
• Franz-Josef Meyer-Almes and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 837–844, doi:10.3762/bjoc.18.84

• of varying length and the evaluation of their HDAC inhibitory activity. Results and Discussion Chemistry Commonly, hydroxamic acids (N-hydroxyamides) are prepared by coupling activated carboxylic acids with O-protected hydroxylamine [23][24][25] or by treatment of esters with hydroxylamine [26][27

The stereochemical course of 2-methylisoborneol biosynthesis

• Binbin Gu,
• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2022, 18, 818–824, doi:10.3762/bjoc.18.82

• biosynthesis of 1 can also be reconstituted in vitro through coupling of dimethylallyl diphosphate (DMAPP) with 2-methyl-IPP (2-Me-IPP; IPP = isopentenyl diphosphate) to 2-Me-GPP using farnesyl diphosphate synthase (FPPS), followed by cyclization through 2MIBS to 1 [26]. A recently described methyltransferase

• methylation of DMAPP to 2-Me-IPP with a hypothetical MT, followed by coupling of DMAPP and 2-Me-IPP to 2-Me-GPP by FPPS and cyclization to 1 by 2MIBS. Synthesis of (R)- and (S)-2-Me-LPP. Hypothetical mechanism for the isomerization of (S)-2-Me-LPP through 2-Me-GPP to (R)-2-Me-LPP. Supporting Information

Continuous flow synthesis of azobenzenes via Baeyer–Mills reaction

• Jan H. Griwatz,
• Anne Kunz and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2022, 18, 781–787, doi:10.3762/bjoc.18.78

• used Baeyer–Mills coupling reaction was adopted to a continuous flow setup. The versatility was demonstrated with a scope of 20 substances and the scalability of this method exemplified by the synthesis of >70 g of an azobenzene derivative applied in molecular solar thermal storage (MOST) systems

• reliable synthesis of symmetric ABs in high yields via a Cu-catalyzed oxidative coupling of aniline derivatives [17]. This synthesis can be also used for the formation of non-symmetric AB, however, only for a selected set of anilines. One of the most applied methods to access non-symmetric azobenzenes is

• report a continuous flow synthesis of non-symmetric AB compounds via the Baeyer–Mills reaction, which allows to obtain large quantities of products from different substrates in a fast and efficient manner. Results and Discussion For optimization of the Baeyer–Mills coupling in continuous flow the

A trustworthy mechanochemical route to isocyanides

• Francesco Basoccu,
• Federico Cuccu,
• Federico Casti,
• Rita Mocci,
• Claudia Fattuoni and
• Andrea Porcheddu

Beilstein J. Org. Chem. 2022, 18, 732–737, doi:10.3762/bjoc.18.73

• reaction. This is why a solid anhydride, like the isatoic one, captured our interest, but unfortunately, the results were unsatisfying. A second idea relied on traditional coupling reagents, especially carbodiimides (DIC and DCC) [25] and CDI [26][27][28][29]. The former should generate a urea derivative