Two new lanostanoid glycosides isolated from a Kenyan polypore Fomitopsis carnea

• Winnie Chemutai Sum,
• Sherif S. Ebada,
• Didsanutda Gonkhom,
• Cony Decock,
• Rémy Bertrand Teponno,
• Josphat Clement Matasyoh and
• Marc Stadler

Beilstein J. Org. Chem. 2023, 19, 1161–1169, doi:10.3762/bjoc.19.84

• unsaturation in its structure. The 1H, 13C NMR, and HSQC spectral data of compound 1 (Table 1) revealed the presence of forty-three carbon resonances sorted into eight methyl, fourteen methylenes (one olefinic), ten methine and eleven unprotonated carbon atoms. This includes three carbonyl carbons at δC 177.4

• methylene groups at δH 2.65/2.69 (H2-2') and δH 2.69/2.72 (H2-4') to an ester carbonyl (δC 172.4, C-1') and a carboxyl (δC 175.0, C-5'), respectively. In addition, both methylene groups together with a methyl singlet at δH 1.38 (s, H3-6') disclosed key HMBC correlations to a quaternary oxygenated carbon at

• confirmation of the positions of the 3-hydroxy-3-methylglutaroyl and β-ᴅ-glucopyranosyl moieties was provided by the HMBC spectrum which exhibited key correlations from H-3 to C-1' and from H-20 (δH 2.40, td, J = 11.0, 3.5 Hz)/H-1'' (δH 5.49, d, J = 8.1 Hz) to a carbonyl carbon at δC 177.4 (C-21). Hence, their

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Synthesis of imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazines via a base-induced rearrangement of functionalized imidazo[4,5-e]thiazolo[2,3-c][1,2,4]triazines

• Dmitry B. Vinogradov,
• Alexei N. Izmest’ev,
• Angelina N. Kravchenko,
• Yuri A. Strelenko and
• Galina A. Gazieva

Beilstein J. Org. Chem. 2023, 19, 1047–1054, doi:10.3762/bjoc.19.80

• . however, acid 5l underwent partial transformations even under these conditions and was not isolated as individual substance. We assumed the following mechanism for the formation of products 9 (Scheme 8). Redistribution of the electron density in the acid molecule 5 after protonation of the carbonyl group

• ][1,2,4]triazine and imidazo[4,5-e][1,3]thiazino[2,3-c][1,2,4]triazine. Thus, the signals of the corresponding protons for isomeric acids 4a and 5a appeared at δ 5.59 and 6.23 ppm, respectively, that is obviously due to a deshielding effect of the carbonyl group of the products 4a and 5a as well as its

• closer location in structures 5 (Figure 3). In the downfield region of the 13C NMR spectra registered without proton decoupling for isomeric acids 4a and 5a, the carbon atom doublets of the carboxyl groups, carbonyl groups of thiazole (for 4a) or thiazine (for 5a) cycles, as well as multiplets of

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• carbonyl oxygen of 69 in the ternary complex, thus bringing more rigidity in the three dimensional transition state (Scheme 18) [46]. In 2021, Chen and co-workers documented a chiral phosphoric acid P17-catalyzed aza-Friedel–Crafts process between racemic 2,3-dihydroisoxazol-3-ol derivatives 76 and

• a hydroxyquinoline-substituted aza-quaternary stereocenter in the 3 position. Most of the examples in this report involved 6-hydroxyquinoline as nucleophile whereas two examples each were presented with 5- and 7-hydroxyquinolines, respectively. Both the imine nitrogen and the carbonyl oxygen of the

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• carbonyl carbon to form the 5-membered ring E bearing the iminium ion. Finally, N-substituted amines 67 were obtained after deprotonation/protonation, dehydration, and aromatization steps as shown in Scheme 32b. In another report, Ozaki et al. [87] used the Clauson–Kaas approach to synthesize sulfonic

Intermediates and shunt products of massiliachelin biosynthesis in Massilia sp. NR 4-1

• Till Steinmetz,
• Blaise Kimbadi Lombe and
• Markus Nett

Beilstein J. Org. Chem. 2023, 19, 909–917, doi:10.3762/bjoc.19.69

• ) and a proton resonance at δH 3.73 ppm (H-16). Both H-16 and H-14 show HMBC correlations to the carbonyl C-15. It can therefore be concluded that a methyl ester function replaced the carboxylic acid function of compound 1. Measurements of the optical rotation of 2 were not possible due to the low

First synthesis of acylated nitrocyclopropanes

• Kento Iwai,
• Rikiya Kamidate,
• Khimiya Wada,
• Haruyasu Asahara and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2023, 19, 892–900, doi:10.3762/bjoc.19.67

• ) halogenation, and 3) ring closure (Scheme 2). β-Nitrostyrene 2 serves as an appropriate acceptor for conjugate addition by diethyl malonate (3a) to afford adduct 4a, in which the methine group flanked by two carbonyl groups is readily halogenated, and the subsequent intramolecular nucleophilic substitution by

• was not given for the different coupling constants between diester 1a and diketone 1b’. In the 13C NMR spectrum of diester 1a, two separate signals of carbonyl groups were observed at 163.2 and 163.3 ppm, indicating that the two ester functionalities were not equivalent. Moreover, the spectrum of

• compound 8b revealed only a single signal of a carbonyl carbon at 193.2 ppm, and a signal of a quaternary carbon at 167.0 ppm, which could not be assigned. These spectral data prompted us to reconsider the structure of compound 8b. The reaction of chlorinated nitrostyrene 2b with acetylacetone (3b) was in

Asymmetric tandem conjugate addition and reaction with carbocations on acylimidazole Michael acceptors

• Brigita Mudráková,
• Renata Marcia de Figueiredo,
• Jean-Marc Campagne and
• Radovan Šebesta

Beilstein J. Org. Chem. 2023, 19, 881–888, doi:10.3762/bjoc.19.65

• solubility in water. Among exceptional properties belongs to easy post-transformation of acylimidazoles to common carbonyl analogs. These tunable properties allow the use of acylimidazoles in chemical biology research, which includes chemical synthesis of proteins/peptides, structure analysis, and functional

• products [20]. A salient feature of conjugate additions of organometallic reagents is that they generate reactive metal enolates as primary products. These enolates can be used in a variety of subsequent transformations [21]. Chiral enolates generated by conjugate additions react with carbonyl compounds

A fluorescent probe for detection of Hg²⁺ ions constructed by tetramethyl cucurbit[6]uril and 1,2-bis(4-pyridyl)ethene

• Xiaoqian Chen,
• Naqin Yang,
• Yue Ma,
• Xinan Yang and
• Peihua Ma

Beilstein J. Org. Chem. 2023, 19, 864–872, doi:10.3762/bjoc.19.63

• outside the cavity, forming a 1:1 inclusion complex with TMeQ[6]. Figure 4b shows that the hydrogen atoms on the G molecule form C–H30···O1, C–H30···O2 and C–H31···O4 hydrogen bonds with the carbonyl oxygen and carbon atoms on TMeQ[6], and the bond distances are 2.163, 2.707 and 2.228 Å, respectively. In

• Figure 4c, the hydrogen atoms of G and the carbonyl oxygen of TMeQ[6] form C–H22···O1, C–H26···O1, C–H25···O4 and C–H27···O4 hydrogen bonds with bond distances of 2.370, 2.474, 2.564 and 2.685 Å, respectively. These interactions contribute to the formation of stable inclusion complexes. Figure 4d is a

• one-dimensional supramolecular chain of G@TMeQ[6], which is composed of hydrogen bonds C24–H···O6 and N13–H···O6 formed by the protons on the pyridyl group outside the cavity and the carbonyl oxygen of the adjacent TMeQ[6] port. The G molecule acts as a medium for connecting two adjacent TMeQ[6]. The

Pyridine C(sp²)–H bond functionalization under transition-metal and rare earth metal catalysis

• Haritha Sindhe,
• Malladi Mounika Reddy,
• Karthikeyan Rajkumar,
• Akshay Kamble,
• Amardeep Singh,
• Anand Kumar and
• Satyasheel Sharma

Beilstein J. Org. Chem. 2023, 19, 820–863, doi:10.3762/bjoc.19.62

• pyridine syntheses have relied on the condensation of carbonyl compounds and amines for a very long time [11]. The classical methods for the synthesis of functionalized pyridine include the Hantzsch pyridine synthesis and the Bohlmann–Rahtz synthesis (Scheme 1a and b). Furthermore, alternative

Eschenmoser coupling reactions starting from primary thioamides. When do they work and when not?

• Lukáš Marek,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2023, 19, 808–819, doi:10.3762/bjoc.19.61

• with a α-haloketone or α-haloester II. The initially formed α-thioiminium salt III can undergo either a base-catalyzed elimination to give nitrile X and thiol IX [10][11][12] or cyclization to give a thiazole XIII or thiazolone XI depending on the substituent at the carbonyl group Y. Both side

• lactam 2 structure involving the replacement of a quaternary carbon carrying two electron-donating methyl groups with an electron-withdrawing carbonyl group (2b → 3). The starting isoquinoline-1,3(2H,4H)-dione was prepared [31] from homophthalic acid and then brominated with NBS to give 4

• nitrogen and carbonyl oxygen, generating both nucleophilic and electrophilic centers, i.e., a free amino group and protonated carbonyl group, which is much more prone to nucleophilic attack than a carbonyl group itself. Quantum calculations (see the left side of Figure 2) show that the relative stabilities

Facile access to 3-sulfonylquinolines via Knoevenagel condensation/aza-Wittig reaction cascade involving ortho-azidobenzaldehydes and β-ketosulfonamides and sulfones

• Ksenia Malkova,
• Andrey Bubyrev,
• Stanislav Kalinin and
• Dmitry Dar’in

Beilstein J. Org. Chem. 2023, 19, 800–807, doi:10.3762/bjoc.19.60

• modification of various substrates, such as 3-bromoquinolines [52][53][54][55], quinoline-3-boronic acids [56], and diazonium salts [57]. When considering general methods for the quinoline core formation, aromatic ortho-substituted carbonyl compounds attract attention as decent and easily available reagents

• . While the ortho-amino carbonyl reagents are not always easily accessible and sometimes unstable (e.g., aminoaldehydes), both o-azidoaldehydes [58][59][60][61][62][63][64][65] and o-azidoketones [66][67][68][69] have been proved to be appropriate substrates for quinoline derivatives synthesis. Recently

• carbonyl group deactivation. Furthermore, while implementing the protocol for 2-azidoquinoline-3-carbaldehyde (1t), a low conversion of this reagent was detected, which can be explained by the fact that 1t tends to exist in the inactive tetrazole form. In addition, our attempt to involve Boc-protected

Non-peptide compounds from Kronopolites svenhedini (Verhoeff) and their antitumor and iNOS inhibitory activities

• Yuan-Nan Yuan,
• Jin-Qiang Li,
• Hong-Bin Fang,
• Shao-Jun Xing,
• Yong-Ming Yan and
• Yong-Xian Cheng

Beilstein J. Org. Chem. 2023, 19, 789–799, doi:10.3762/bjoc.19.59

• sp2), one carbonyl carbon, and two sp2 quaternary carbons. The 1H–1H COSY spectrum (Figure 2 and Figure S29 in Supporting Information File 1) of compound 7 disclosed the existence of correlations of H2-2 (δ 2.29, 2.08)/H-3 (δH 1.91, 1.93)/H2-4 (δH 1.38, 1.24)/H2-5 (δH 2.03, 2H)/H-6 (δH 5.12), H-3 (δH

• , H3-16, H3-17), and 0.94 (d, J = 6.2 Hz, 3H, H3-15)]. The 13C NMR and DEPT spectra (Table 4 and Figure S35 in Supporting Information File 1) show that this substance contains 17 resonances, including three methyls, eight methylenes (one of them oxygenated), three methines (two sp2), one carbonyl

Synthesis of substituted 8H-benzo[h]pyrano[2,3-f]quinazolin-8-ones via photochemical 6π-electrocyclization of pyrimidines containing an allomaltol fragment

• Constantine V. Milyutin,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Mikhail E. Minyaev and
• Valeriya G. Melekhina

Beilstein J. Org. Chem. 2023, 19, 778–788, doi:10.3762/bjoc.19.58

• guanidine C. Finally, the intramolecular cyclization of the guanidine moiety and the carbonyl group leads to the target pyrimidine 9. After the general synthetic method for pyrimidines containing the allomaltol fragment had been established, the photochemical behavior of the obtained compounds 9 was

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines

• Joydev K. Laha,
• Pankaj Gupta and
• Amitava Hazra

Beilstein J. Org. Chem. 2023, 19, 771–777, doi:10.3762/bjoc.19.57

• were used as the substrates in this reaction, N-arylimines were not isolated. Rather, an amide, in some cases, was isolated via oxidation of the benzylic methylene to a carbonyl group [14]. In the quest of a new method for the synthesis of N-arylsulfonylimines, we questioned ourselves whether N

Synthesis of imidazo[1,2-a]pyridine-containing peptidomimetics by tandem of Groebke–Blackburn–Bienaymé and Ugi reactions

• Oleksandr V. Kolomiiets,
• Alexander V. Tsygankov,
• Maryna N. Kornet,
• Aleksander A. Brazhko,
• Vladimir I. Musatov and
• Valentyn A. Chebanov

Beilstein J. Org. Chem. 2023, 19, 727–735, doi:10.3762/bjoc.19.53

• carbonyl component was proposed, but these aldehydes did not have the structure of imidazo[1,2-a]pyridine. Interestingly, in 2019 [1], the synthesis of the amine component using GBB-3CR and the modification of the imidazo-pyrimidine scaffold by a peptidomimetic chain was carried out using the Ugi reaction

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• ) [66]. Variations of this reaction include alkyne metathesis [67] and carbonyl metathesis [68]. Ring-closing metathesis (RCM) gave access to a series of dibenzo[b,f]heteropines, as reported by Matsuda and Sato [31] (Scheme 25). The authors synthesised a series of Si-, Sn-, Ge- and B-tethered dienes 118

• ) chloride (Scheme 26). Alkyne–carbonyl metathesis is proposed to proceed via [2 + 2] cycloaddition and –reversion steps, catalysed by a Brønsted or Lewis acid, with the catalyst proposed to form a σ-complex with the carbonyl group and/or a π-complex with the alkyne [68]. 3.7 Hydroarylation The construction

Cassane diterpenoids with α-glucosidase inhibitory activity from the fruits of Pterolobium macropterum

• Sarot Cheenpracha,
• Ratchanaporn Chokchaisiri,
• Lucksagoon Ganranoo,
• Sareeya Bureekaew,
• Thunwadee Limtharakul and
• Surat Laphookhieo

Beilstein J. Org. Chem. 2023, 19, 658–665, doi:10.3762/bjoc.19.47

• revealed the presence of hydroxy (3429 cm−1) and carbonyl (1733 cm−1) groups. The UV absorption band maximum at λmax 283 nm and five downfield-shifted carbon signals at δC 169.8 (C-16), 163.8 (C-13), 149.3 (C-12), 111.6 (C-11), and 109.6 (C-15) in the 13C NMR data suggested the presence of the α,β

• . The 13C NMR and DEPT spectra, combined with HMQC correlations (Table 1) showed 20 resonances for carbon signals accounting for four methyls, five sp3 methylenes, five methines (two olefinics at δC 111.6, 109.6), and six quaternary carbons (one carbonyl at δC 169.8, two olefinics at δC 163.8, 149.3

• unsaturation required the presence of two heterocyclic rings in the molecule. The presence of an ester carbonyl signal (δC 167.0) and a deshielded oxygenated carbon resonance at C-12′ (δC 104.1) implied the formation of six-membered ring via an ester bond between C-16 and C-12′. In addition, an epoxide moiety

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

• α,β-unsaturated carbonyl compounds [2]. In particular, the last-mentioned method is highly synthetically relevant. This approach has the advantage of being more selective and affording more molecular complexity in one step. In addition, transition-metal catalysis allows the introduction of

• , which is otherwise not easy to introduce into the C-2 position of carbonyl compounds. Finally, the benzodithiolyl group can be reduced into a methyl group (Scheme 29). Conjugate additions with trialkylaluminum reagents Conjugate additions of trialkylaluminum reagents are somewhat less populated as a

• derivatives have been found to exhibit potent biological activities, which has led to the development of several FDA-approved drug molecules [73][74]. Following the seminal works of Hosomi [75] and Miyaura [76], the synthesis of β-boron-substituted carbonyl compounds by conjugate addition of boron species to

C3-Alkylation of furfural derivatives by continuous flow homogeneous catalysis

• Grédy Kiala Kinkutu,
• Catherine Louis,
• Myriam Roy,
• Juliette Blanchard and
• Julie Oble

Beilstein J. Org. Chem. 2023, 19, 582–592, doi:10.3762/bjoc.19.43

• . Unfortunately, with this catalyst, repeatability problems were detected (yield fluctuation of approximately 20%) which could be assigned to the low solubility of this catalyst in toluene. In order to overcome these problems, we synthesized triruthenium carbonyl complexes with phosphine ligand(s), namely

• formation of ruthenium aggregates [43]. We therefore propose that the active species is a mononuclear carbonyl complex in which the ruthenium is coordinated to the two nitrogen atoms of the directing group (amino-imine). Preheating for 5 minutes at 130 °C would generate it from [Ru3(CO)11(L)], which would

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• be envisioned for the carbonannulation of diazabicyclic alkenes with 2-formylphenylboronic acid up to the last step which likely operates through a β-hydride elimination of the Rh(I) alkoxide, furnishing the final carbonyl-containing product. In 2013, Lautens reported the synthesis of oxazolidinone

• alkene of the azabicycle producing 154. A C–N bond cleavage occurs creating π-allylrhodium 155. Subsequently, the phenol oxygen then adds to the π–allyl species in a cis fashion, furnishing 156 which is proposed to be the enantiodetermining step. The carbonyl–rhodium species 156 inserts into the alkene

• significant steric interactions between the carbonyl and aryl groups. The authors proposed that the Zn(OTf)2 Lewis acid cocatalyst may activate the bridging oxygen of the oxabenzonorbornadiene lowering the

Mechanochemical solid state synthesis of copper(I)/NHC complexes with K₃PO₄

• Ina Remy-Speckmann,
• Birte M. Zimmermann,
• Mahadeb Gorai,
• Martin Lerch and
• Johannes F. Teichert

Beilstein J. Org. Chem. 2023, 19, 440–447, doi:10.3762/bjoc.19.34

• the standard reactions for catalytic hydrogenations with copper(I)/NHC complexes [4]. In this vein, we tested complex 5 from solid and liquid phase synthesis in the catalytic hydrogenation of esters, carbonyl compounds and in the semihydrogenation of alkynes. In the catalytic hydrogenation of ethyl

• complex 5 was never evaluated in this reported reaction. Therefore, 5bm behaves similarly to other copper(I)/NHC complexes in this transformation [54][55][56][57][58][59][60]. The catalytic 1,2-reduction of carbonyl compounds is mainstay for copper(I)/NHC complexes [61][62][63][64][65][66][67], which is

Dipeptide analogues of fluorinated aminophosphonic acid sodium salts as moderate competitive inhibitors of cathepsin C

• Karolina Wątroba,
• Małgorzata Pawełczak and
• Marcin Kaźmierczak

Beilstein J. Org. Chem. 2023, 19, 434–439, doi:10.3762/bjoc.19.33

• as potential inhibitors of cathepsins. The phosphorus atom by default should mimic the tetrahedral intermediate, but this role may also be played by the hydroxy group present in hydroxyphosphonates, which mimic the carbonyl carbon in the peptide bond by forming a hydrogen bond with the amino group of

Combretastatins D series and analogues: from isolation, synthetic challenges and biological activities

• Jorge de Lima Neto and
• Paulo Henrique Menezes

Beilstein J. Org. Chem. 2023, 19, 399–427, doi:10.3762/bjoc.19.31

• only be favorable after the macrolactonization step. The authors used a convergent route for the formal synthesis of 2. Reaction of 4-bromobenzaldehyde (52) with a commercially available stabilized Wittig reagent led to the formation of the corresponding ester 53. Further reduction of the carbonyl

Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis

• Nicoleta G. Hădărugă,
• Gabriela Popescu,
• Dina Gligor (Pane),
• Cristina L. Mitroi,
• Sorin M. Stanciu and
• Daniel Ioan Hădărugă

Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30

• OH groups from water molecules), CH bonds (especially from the CH2 and CH3 groups), bands corresponding to the aromatic CC bonds, and the carbonyl C=O bond. The most relevant FTIR band for these compounds is the asymmetric stretching vibration of the C=O bonds, νasC=O, which appears around 1633–1651