Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• and abundant source of biomass-derived molecules. Decarboxylative transformations of carboxylic acids into value-added chemical products (such as biofuels) are a key objective in organic synthesis [25]. In 2014, Wallentin and co-workers reported a type of decarboxylation reaction of α-amino acids, α

[3 + 2] Cycloaddition with photogenerated azomethine ylides in β-cyclodextrin

• Margareta Sohora,
• Leo Mandić and
• Nikola Basarić

Beilstein J. Org. Chem. 2020, 16, 1296–1304, doi:10.3762/bjoc.16.110

• reactions [8]. Azomethine ylides can be formed by several photochemical or thermal catalytic methods [5][6][7], including photodecarboxylation of phthalimide derivatives of α-amino acids such as N-phthaloylglycine (1) [9][10]. Phthalimide is a versatile chromophore that has been used in the synthesis of

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• nitrile 48a with 30% HCl aq/acetic acid, gave the 4-fluorophenylalanine·HCl 49a in a good overall yield (67%) [47] (Scheme 11). 1.4. Hydrolysis of Erlenmeyer’s azalactone A multistep Erlenmeyer azalactone synthesis was reported as an important method for the synthesis of fluorinated α-amino acids 53a–h

• , chloro, bromo, methoxy, acetyl, cyano, nitro, and trifluoromethyl, were well-tolerated and afforded the corresponding anti-β-fluoro-α-amino acids 163a–l in moderate to excellent yields [78] (Scheme 40). 3. Synthesis of β,β-difluorophenylalanine derivatives of type IV via 2-phenyl-2,2-difluoroacetaldehyde

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• using 4 mol % of tetra-n-butylammonium fluoride (TBAF) as an activator of TMSCN (conditions B). Following this second protocol, the primary α-aminonitriles were rapidly prepared in relevant yields (up to 87%) and converted to the corresponding α-amino acids by hydrolysis of the nitrile (Scheme 57

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

• with ester hydrolysis and debenzylation gave enantiomerically pure (2S,3S,4R)-110 and two stable derivatives (2S,3S,4R)-114 and (2S,3S,4R)-115 (Scheme 29). Amino acids and derivatives α-Amino acids: Homochiral amino alcohols of general formula RCH(NH2)CH2OH as precursors of α-amino acids can be

• (R)-116 as the hydrochloride salt [83]. Other α-amino acids of general formula RCH2CH(NH2)COOH, e.g., R = Me, iPr, PhCH2, were prepared in a similar way [76]. A straightforward synthesis of N-Boc-ᴅ-3,3-diphenylalanine ((R)-122) was carried out from the aziridine menthyl ester (2S,1'R)-5f [84]. Phenyl

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis of a novel category of pseudo-peptides using an Ugi three-component reaction of levulinic acid as bifunctional substrate, amines, and amino acid-based isocyanides

• Maryam Khalesi,
• Azim Ziyaei Halimehjani and
• Jürgen Martens

Beilstein J. Org. Chem. 2019, 15, 852–857, doi:10.3762/bjoc.15.82

• acid, aromatic and aliphatic amines and amino acid-based isocyanides. First of all, racemic α-amino acids such as DL-tryptophan, DL-phenylalanine and DL-leucine were used as amine source for the synthesis of isocyanide esters 3 through three sequential reactions [30][31]. The first reaction is

• amino acid-based isocyanides starting from α-amino acids. Synthesis of pseudo-peptides using levulinic acid, isocyanide esters and amines. Proposed mechanism for Ugi-4C-3CR. Supporting Information Supporting Information File 344: Experimental procedures, characterization data and copies of 1H and 13C

Synthesis of C₃-symmetric star-shaped molecules containing α-amino acids and dipeptides via Negishi coupling as a key step

• Sambasivarao Kotha and
• Saidulu Todeti

Beilstein J. Org. Chem. 2019, 15, 371–377, doi:10.3762/bjoc.15.33

• helpful to design star-shaped α-amino acids (AAAs) and they play an important role in biological systems. The tumor necrosis factor (TNF) superfamily belongs to trimeric ligands that form in the shape of C3-symmetric molecules [5]. Trimeric proteins containing star-shaped compounds are also involved in

Green synthesis of new chiral 1-(arylamino)imidazo[2,1-a]isoindole-2,5-diones from the corresponding α-amino acid arylhydrazides in aqueous medium

• Nadia Bouzayani,
• Jamil Kraїem,
• Sylvain Marque,
• Yakdhane Kacem,
• Abel Carlin-Sinclair,
• Jérôme Marrot and
• Béchir Ben Hassine

Beilstein J. Org. Chem. 2018, 14, 2923–2930, doi:10.3762/bjoc.14.271

• ]isoindole-2,5(3H,9bH)-diones [6] and 1,2,3,9b-tetrahydro-5H-imidazo[2,1-a]isoindol-5-ones [13] has been described by Katritzky et al. using α-aminoamides and diamines, respectively. Also, the imidazo[2,1-a]isoindole-2,5-dione derivatives of primaquin have been synthesized from α-amino acids [14]. Focusing

• directed toward the development of environmentally safe conditions for the synthesis of heterocyclic compounds starting from natural (L)-α-amino acids [19][20][21][22][23] and the reactivity of α-amino acid phenylhydrazides [24][25], we now report a green and eco-friendly procedure for the synthesis of new

Hypervalent iodine(III)-mediated decarboxylative acetoxylation at tertiary and benzylic carbon centers

• Kensuke Kiyokawa,
• Daichi Okumatsu and
• Satoshi Minakata

Beilstein J. Org. Chem. 2018, 14, 1046–1050, doi:10.3762/bjoc.14.92

• operation, and the use of readily available and environmentally friendly oxidants. However, despite the great potential of this approach with respect to a decarboxylative C–O bond-forming reaction, the oxidation system was only applied to reactions of uronic acids and α-amino acids [22][23][24], and further

Novel amide-functionalized chloramphenicol base bifunctional organocatalysts for enantioselective alcoholysis of meso-cyclic anhydrides

• Lingjun Xu,
• Shuwen Han,
• Linjie Yan,
• Haifeng Wang,
• Haihui Peng and
• Fener Chen

Beilstein J. Org. Chem. 2018, 14, 309–317, doi:10.3762/bjoc.14.19

• stereocontrol in alcoholytic catalytic asymmetric desymmetrizations of meso-cyclic anhydrides is of special interest [1][2][3][4][5][6][7]. Major families originating from natural products include cinchona alkaloids [8][9][10][11][12][13][14][15][16][17] and proteinogenic α-amino acids such as proline [18][19

Quinone-catalyzed oxidative deformylation: synthesis of imines from amino alcohols

• Xinyun Liu,
• Johnny H. Phan,
• Benjamin J. Haugeberg,
• Shrikant S. Londhe and
• Michael D. Clift

Beilstein J. Org. Chem. 2017, 13, 2895–2901, doi:10.3762/bjoc.13.282

• decarboxylative homologation of α-amino acids [32], which demonstrated for the first time that quinone organocatalysts can be utilized to enable oxidative C–C bond cleavage to provide versatile imine intermediates. To further exploit the utility of this chemistry, we sought to develop a new method for the

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• and Mannich acceptors [20][21][22][23]. Enolate anions derived from azlactone are effective intermediates for the functionalization of α-amino acids. However, the acylation of the enolate ion by another azlactone has been less reported in the literature [24][25][26]. This transformation affords an

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• conventional functionalization or (hetero)cyclization [15][16][17]. Among these reagents, trifluoromethylketimines have drawn much research interest in recent years as key starting materials for the synthesis of trifluoromethyl-substituted amines [18][19], α-amino acids [20][21][22][23] as well as nitrogen

Synthesis of 1,3-cis-disubstituted sterically encumbered imidazolidinone organocatalysts

• Jan Wallbaum and
• Daniel B. Werz

Beilstein J. Org. Chem. 2017, 13, 2577–2583, doi:10.3762/bjoc.13.254

• -cis-disubstituted diastereomers of up to 52%. Different methyl amides derived from α-amino acids and bulky aromatic carbaldehydes were employed to access the MacMillan-type catalysts. The key to the success is the activation with ytterbium triflate as Lewis acid and the use of dehydrating molecular

Homologated amino acids with three vicinal fluorines positioned along the backbone: development of a stereoselective synthesis

• Raju Cheerlavancha,
• Ahmed Ahmed,
• Yun Cheuk Leung,
• Aggie Lawer,
• Qing-Quan Liu,
• Marina Cagnes,
• Hee-Chan Jang,
• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2017, 13, 2316–2325, doi:10.3762/bjoc.13.228

• ][10] provide opportunities for functionalisation in ways not possible in natural α-amino acids. There is the ability to place heteroatoms along the amino acid backbone, or to incorporate two or more functionalised side chains per amino acid residue, and this results in a variety of stereochemical

• progression in the study of fluorinated amino acids develops into the concept of α,β,γ-trifluoro-δ-amino acids (e.g., 6, Figure 1). δ-Amino acids such as 6 are of special interest because they have the same backbone length as a dipeptide of α-amino acids, and thus may potentially be substituted for a two

Synthesis of 2-aminosuberic acid derivatives as components of some histone deacetylase inhibiting cyclic tetrapeptides

• Shital Kumar Chattopadhyay,
• Suman Sil and
• Jyoti Prasad Mukherjee

Beilstein J. Org. Chem. 2017, 13, 2153–2156, doi:10.3762/bjoc.13.214

• in the preparation of α-amino acids [21][22][23][24][25][26][27] and few useful general guidelines have emerged from these studies. Pleasingly, cross metathesis of our building block 11 with tert-butyl acrylate (13a) proceeded quickly in the presence of Grubbs’ 2nd generation catalyst [(1,3-bis(2,4,6

Chiral phase-transfer catalysis in the asymmetric α-heterofunctionalization of prochiral nucleophiles

• Johannes Schörgenhumer,
• Maximilian Tiffner and
• Mario Waser

Beilstein J. Org. Chem. 2017, 13, 1753–1769, doi:10.3762/bjoc.13.170

• of the essential transformations in (bio)organic chemistry and the importance of the hereby accessed chiral α-aminocarbonyl compounds like, e.g., α-amino acids or others cannot be overestimated [135]. Accordingly, it comes as no surprise that the development of asymmetric catalytic methods towards

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• -acylimine 2 also reduces the general reactivity of this reaction system. Recently, we have described a simple and efficient two-step transformation of N-acylated α-amino acids to 1-(N-acylamino)alkyltriphenylphosphonium salts 1 (Z = PPh3+ A−) [18]. We have also demonstrated that the obtained stable

• Otezla), a tumor necrosis factor-α (TNF-α) inhibitor used for the treatment of psoriasis, psoriatic dermatitis and other inflammatory diseases related to the immune system [31]. Results and Discussion 1-Imidoalkylphosphonium salts 5 were synthesized in a three-step procedure starting from α-amino acids

• side reactions (for example Kolbe-dimerization), the yields were only poor (10–35%) [33][34]. According to our previously reported procedure for the electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids [18], amino acid derivatives 6 were converted to N-(1-methoxyalkyl)imides 7. The

Switchable highly regioselective synthesis of 3,4-dihydroquinoxalin-2(1H)ones from o-phenylenediamines and aroylpyruvates

• Juraj Dobiaš,
• Marek Ondruš,
• Gabriela Addová and
• Andrej Boháč

Beilstein J. Org. Chem. 2017, 13, 1350–1360, doi:10.3762/bjoc.13.132

• -fluoronitrobenzenes 28 with the derivatives of α-amino acids [29][30][31]. The product of spontaneous cyclization of 30 was obtained after reduction of nitro derivative 29. Through mild oxidation, compound 30 provides the required quinoxalin-2(1H)-one 31 (Scheme 5). The obvious disadvantage in this case is the

The synthesis of α-aryl-α-aminophosphonates and α-aryl-α-aminophosphine oxides by the microwave-assisted Pudovik reaction

• Erika Bálint,
• Ádám Tajti,
• Anna Ádám,
• István Csontos,
• Konstantin Karaghiosoff,
• Mátyás Czugler,
• Péter Ábrányi-Balogh and
• György Keglevich

Beilstein J. Org. Chem. 2017, 13, 76–86, doi:10.3762/bjoc.13.10

• ; Introduction α-Aminophosphonates and related derivatives, considered as the structural analogues of α-amino acids, have significant importance, especially in medicinal [1][2][3] and agricultural chemistry [4][5], due to their potential biological activity. The two major synthetic routes towards α

A chiral analog of the bicyclic guanidine TBD: synthesis, structure and Brønsted base catalysis

• Mariano Goldberg,
• Denis Sartakov,
• Jan W. Bats,
• Michael Bolte and
• Michael W. Göbel

Beilstein J. Org. Chem. 2016, 12, 1870–1876, doi:10.3762/bjoc.12.176

• control exerted by 10 when used as a catalyst. In this article we describe the synthesis of guanidine 10 together with some initial applications as a chiral Brønsted base. Results and Discussion Previous syntheses of bicylic guanidines 2 and 6–9 started from enantiomerically pure α-amino acids [6][8][10

Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

• Hee Seung Jang,
• Yubin Kim and
• Dae Young Kim

Beilstein J. Org. Chem. 2016, 12, 1551–1556, doi:10.3762/bjoc.12.149

• organocatalyst; ketimines; organocatalysis; squaramide; Introduction α-Aminophosphonate derivatives are important compounds as structural mimics of natural α-amino acids [1][2][3]. Chiral α-aminophosphonates have been shown a wide range of biological activities including antibacterial [4] and anticancer

1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

• Antonia Mielgo and
• Claudio Palomo

Beilstein J. Org. Chem. 2016, 12, 918–936, doi:10.3762/bjoc.12.90

• = S) analogues of these oxazol-4(5H)-ones have been demonstrated to be very interesting templates in asymmetric catalysis. In these cases the hydrolysis of the adducts coming from an asymmetric reaction can provide enantioenriched α-hydroxy acids (X = O), N-substituted α-amino acids (X = NR’) or α

• )-ones 1 as pronucleophiles in organocatalyzed Michael addition reactions 2-Thio-1H-imidazol-4(5H)-ones 1 (R = SBn) have been reported to be effective equivalents of N-subtituted (alkyl, aryl, allyl) α-amino acids in conjugate addition reactions to both, nitroalkenes and α-silyloxy enones as Michael

• pronucleophiles in asymmetric catalytic reactions. The results show that they are efficient substrates in reactions which involve the creation of a tetrasubstituted stereogenic center. Further elaboration of adducts coming from these reactions gives access to N-substitued α-amino acids in the case of imidazolones