A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

• Wiesława Perlikowska,
• Remigiusz Żurawiński and
• Marian Mikołajczyk

Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215

• at C-5. In fact, 1a and 1c were obtained through a two-step sequence starting with the methylation of (−)-1a and (+)-1c followed by a one-pot Mitsunobu esterification–hydrolysis as shown in Scheme 6. In detail, treatment of rosaprostols (−)-1a and (+)-1c with diazomethane gave the corresponding

• rosaprostol methyl esters (−)-9 and (+)-9 in yields higher than 90%. Then the esters 9 were subjected to a Mitsunobu esterification under standard conditions (THF, rt) using p-nitrobenzoic acid (PNBA), triphenylphosphine and diisopropyl azodicarboxylate (DIAD). The p-nitrobenzoic acid esters (+)-10 and (−)-10

Silica-supported sulfonic acids as recyclable catalyst for esterification of levulinic acid with stoichiometric amounts of alcohols

• Raimondo Maggi,
• N. Raveendran Shiju,
• Veronica Santacroce,
• Giovanni Maestri,
• Franca Bigi and
• Gadi Rothenberg

Beilstein J. Org. Chem. 2016, 12, 2173–2180, doi:10.3762/bjoc.12.207

• context, levulinic acid, which is easily obtained from cellulose, is valuable since it can be transformed into a variety of industrially relevant fine chemicals. Here we present a simple protocol for the selective esterification of levulinic acid using solid acid catalysts. Silica supported sulfonic acid

• : esterification; heterogeneous catalysis; renewable feedstocks; supported organic catalysts; sustainable chemistry; Introduction Vegetal biomass is mankind’s only source of renewable carbon on a human timescale. It is abundantly available, with the potential of replacing fossil-based carbon on a scale sufficient

• levulinic esters [19][20][21][22]. Homogeneous Brønsted acids could catalyse the esterification of levulinic acid in the presence of alcohols and reports on this reactivity date back to the nineties [23]. Although this route could ensure high chemical yields, it still presents a series of drawbacks. In

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• acidic polyionic liquid by the copolymerization of a zwitterionic liquid based on vinylpyridinium, styrene and ethyleneglycol dimethacrylate (Scheme 4) [44]. The resulting PIL with particle sizes of about 0.5–3 mm, was an efficient catalyst for a series of esterification reactions of different acids

Potent triazine-based dehydrocondensing reagents substituted by an amido group

• Munetaka Kunishima,
• Daiki Kato,
• Nobu Kimura,
• Masanori Kitamura,
• Kohei Yamada and
• Kazuhito Hioki

Beilstein J. Org. Chem. 2016, 12, 1897–1903, doi:10.3762/bjoc.12.179

• reactions; amido substituents; dehydrocondensing reactions; Fischer-type esterification; triazines; Introduction We previously reported that dehydrocondensing reactions between carboxylic acids 1 and amines 2 to give amides 3 efficiently proceed in water or alcohols in the presence of the dehydrocondensing

• esterification of 3-phenylpropanoic acid (1a) in neat MeOH were studied (Figure 3). Although X was shown to exist as a dihydrate by elemental analysis and single-crystal X-ray structure analysis, the yield of methyl 3-phenylpropanoate was quantitative. The rate of esterification with X was faster than that with

• -forming reactions. Time courses of the basic Fischer-type esterification. Dehydrocondensing reactions using DMT-MM or DMT-Am, and a catalytic amide-forming reaction. Synthesis of amido-substituted chlorotriazines. Amide-forming reactions using chlorotriazines (I–VI) or triazinylammonium salts (VII–X

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

• ][16][17] or from their reduction products, chiral α-amino alcohols [9][18]. In contrast, our approach used the racemic ester rac-12 of β-phenylalanine, easily accessible in a Knoevenagel-type condensation of benzaldehyde 11, ammonium acetate and malonic acid, followed by esterification (Scheme 1) [20

Synthesis of the C8’-epimeric thymine pyranosyl amino acid core of amipurimycin

• Pramod R. Markad,
• Navanath Kumbhar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2016, 12, 1765–1771, doi:10.3762/bjoc.12.165

• generated stereocenters, we continued our synthesis with anhydrosugar 12 as its configurations are matching with that of target compound. Thus, TEMPO-mediated selective oxidation of the primary hydroxy group in 12 to acid functionality followed by esterification using diazomethane afforded azido methyl

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Artificial Diels–Alderase based on the transmembrane protein FhuA

• Hassan Osseili,
• Daniel F. Sauer,
• Klaus Beckerle,
• Marcus Arlt,
• Tomoki Himiyama,
• Tino Polen,
• Akira Onoda,
• Ulrich Schwaneberg,
• Takashi Hayashi and
• Jun Okuda

Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124

• framework containing an alcohol function on the 4 position of the central pyridine was chosen (Scheme 2). By either esterification or nucleophilic attack, the spacer with the maleimide group was attached. The ligand was treated with one equivalent of Cu(NO3)2·3H2O leading to the Cu(II) complexes 10–12. By

Stereoselective synthesis of tricyclic compounds by intramolecular palladium-catalyzed addition of aryl iodides to carbonyl groups

• Jakub Saadi,
• Christoph Bentz,
• Kai Redies,
• Dieter Lentz,
• Reinhold Zimmer and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2016, 12, 1236–1242, doi:10.3762/bjoc.12.118

• determined by an X-ray crystal structure analysis of the corresponding p-nitrobenzoate 12a obtained by esterification of the tertiary alcohol under standard conditions (Scheme 4, Figure 1) [13]. The configuration of the second product 11b is only tentatively assigned as depicted since the available data do

Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• ) in order to investigate the possible competition between photogeneration of biradicals and 1O2, the key mechanistic steps in Ch photooxidation. Results and Discussion Preparation of dyads Compounds 1–3 were prepared by esterification of α- or β-Ch with racemic SP following standard procedures [13

• unambiguous stereochemical assignment, authentic samples of 1 and 2 were prepared by direct esterification of (R)- and (S)-SP with α-Ch [17]. Steady-state photolysis In order to investigate photoproducts formation, steady-state irradiation of dichloromethane solutions (ca. 10−3 M) of 1–3 was performed under

A cross-metathesis approach to novel pantothenamide derivatives

• Jinming Guan,
• Matthew Hachey,
• Lekha Puri,
• Vanessa Howieson,
• Kevin J. Saliba and
• Karine Auclair

Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95

• Hoveyda–Grubbs’ 2nd generation catalyst (4). Compounds 8 and 9 were chosen for initial tests with this reaction (Scheme 1). The synthesis of compounds 8 and 9 was carried out as previously described (Scheme 1) except for some improvements in the esterification step [18]. Akinnusi et al. reported using

Nucleic acids through condensation of nucleosides and phosphorous acid in the presence of sulfur

• Tuomas Lönnberg

Beilstein J. Org. Chem. 2016, 12, 670–673, doi:10.3762/bjoc.12.67

• had H-phosphonothioate, rather than phosphate termini. Evidently sulfurization and esterification of H-phosphonate monoesters compete under the experimental conditions. Determination of the regiochemistry of the phosphorothioate linkages To establish the regiochemistry of the phosphorothioate linkages

Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins

• Guozheng Huang,
• Simon Schramm,
• Jörg Heilmann,
• David Biedermann,
• Vladimír Křen and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 662–669, doi:10.3762/bjoc.12.66

• , Prague 4, CZ-14220, Czech Republic 10.3762/bjoc.12.66 Abstract Various Mitsunobu conditions were investigated for a series of flavonolignans (silybin A, silybin B, isosilybin A, and silychristin A) to achieve either selective esterification in position C-23 or dehydration in a one-pot reaction yielding

• alcohols and bulky acids: Cherney and Wang observed an elimination of a serine derivative during esterification experiments [23]. During conversion of substituted benzyl alcohols to amines under Mitsunobu conditions, elimination also occurred [24]. Dehydration under Mitsunobu conditions has been applied in

• and expeditious semi-synthetic preparation of hydnocarpin, hydnocarpin D and isohydnocarpin. Results and Discussion Although silibinin, i.e., silybins A and B, bears three phenolic, one secondary and one primary hydroxy group, selective Mitsunobu esterification typically occurs at the primary C-23 OH

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• . This is followed by a redox esterification of the latter (47) with enals. The overall process constitutes a one-pot synthesis of hydroxamic esters 48 [45]. Notably, both steps can be performed using the single NHC catalyst 22 under same reaction conditions (Scheme 29). This two-step, one-pot synthesis

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• [18][19], decarboxylative alkenylation of cycloalkanes with aryl vinylic carboxylic acids [20][21], trifluoromethylthiolation [22], thiolation [23][24], alkenylation [25][26], dehydrogenation−olefination and esterification [27][28], radical addition/1,2-aryl migration [29], cascade alkylation

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• esterification of CD was promoted by MW irradiation, while the chitosan coupling used a water-soluble carbodiimide, N-(3-dimethylaminopropyl)-N-ethylcarbodiimide hydrochloride, under US. A mild sonication at rt using HDI enabled efficient CDs reticulation in the presence of lipases (Scheme 7) whose biocatalytic

• was observed at concentrations up to 333 μg/mL [73]. Separately, a facile and rapid MW-assisted method in water has been used to derivatize graphene nanosheets with (2-hydroxy)propyl-β-CD. The reaction involved the esterification of the HP-β-CD hydroxy groups by the carboxyl groups of graphene oxide

Recent advances in metathesis-derived polymers containing transition metals in the side chain

• Ileana Dragutan,
• Valerian Dragutan,
• Bogdan C. Simionescu,
• Albert Demonceau and
• Helmut Fischer

Beilstein J. Org. Chem. 2015, 11, 2747–2762, doi:10.3762/bjoc.11.296

• triazolyl unit was first attached to the η4-cyclopentadiene CpCo(I) complex by click reaction of the corresponding alkyne precursor and then the triazolyl-Co scaffold was incorporated into the norbornene monomer 9 by conventional esterification. It is important to note that the cyclopentadienyl-cobalt-1,3

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• was also detected. Furthermore, a significant amount of methyl 2-iodobenzoate (5) was generated through the esterification of a co-product (2-iodobenzoic acid) with methanol. We also tested other iodine(III) reagents such as PhI(OAc)2, PhI(OCOCF3)2 and PhI(OH)(OTs), but they all resulted in lower

• confirmed that the esterification of 2-iodobenzoic acid takes place to give 5 under the reaction conditions; 2-iodobenzoic acid was smoothly converted to 5 in chloroform/methanol solution at 65 °C. Transmetalation of gold(III) complex B with arylsilane 2 affords monoarylated gold(III) intermediate C. The

Synthesis of cyclic N¹-pentylinosine phosphate, a new structurally reduced cADPR analogue with calcium-mobilizing activity on PC12 cells

• Ahmed Mahal,
• Stefano D’Errico,
• Nicola Borbone,
• Brunella Pinto,
• Agnese Secondo,
• Valeria Costantino,
• Valentina Tedeschi,
• Giorgia Oliviero,
• Vincenzo Piccialli and
• Gennaro Piccialli

Beilstein J. Org. Chem. 2015, 11, 2689–2695, doi:10.3762/bjoc.11.289

• 9 we explored two synthetic routes, differing for the degree of esterification at the phosphate moiety, to achieve the cyclization of the 17-membered ring of 4. The treatment of 9 with a mixture of triethylamine/pyridine furnished the phosphodiester product 10 in almost quantitative yield. Instead

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• , Aβ peptide pentapeptide boronic acids 1 and 2 were synthesized by solid-phase peptide synthesis and studied in esterification experiments with polyhydroxylated templates. The bis-hydroxylated dipeptide Hot=Tap serves as a template of adjustable degree of oligomerization which spontaneously forms

• boronic esters with peptides of type 1 and 2. Nuclear magnetic resonance can differentiate between regioisomeric boronic esters and identifies preferred sites of esterification on the dimeric template 9. 2-Formylphenylboronic acid (14) is used to link the parent pentapeptide Leu-Val-Phe-Phe-Ala to the

• example, disulfide [10], acetal [11], imine [12] and boronates [13][14][15][16], to allow the generation of new covalent structures under thermodynamic control. Complete esterification is observed for boronate esters bearing ortho-amines [17]. The conceptual advantage compared to traditional irreversible

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• synthesized in four steps. Esterification with (R)-(+)-citronellic acid (127) yielded a single diastereomer of ester 128. Addition of lithium diisopropylamide to a mixture of 128, trimethylsilyl chloride and triethylamine initiated an Ireland–Claisen rearrangement [63] which gave carboxylic acid 129 in 85

Recent developments in copper-catalyzed radical alkylations of electron-rich π-systems

• Kirk W. Shimkin and
• Donald A. Watson

Beilstein J. Org. Chem. 2015, 11, 2278–2288, doi:10.3762/bjoc.11.248

• and supress polymerization. A detachable ester group can be utilized in order to achieve Z-selective alkene synthesis [37]. In this protocol, an ortho-hydroxy substituted styrene undergoes esterification with a labile α-bromo ester. This positions the reactive radical exclusively on the face of the

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• , where x is the feed molar ratio of MA to PPO-PEO-PPO. The products were characterized by means of 1H NMR and GPC analyses (Figure S1 and Figure S2, Supporting Information File 1). The degree of esterification of BrPEPBr determined by 1H NMR was >99%. Additionally, the GPC curves of PEPxM presented a

Cross metathesis of unsaturated epoxides for the synthesis of polyfunctional building blocks

• Meriem K. Abderrezak,
• Kristýna Šichová,
• Nancy Dominguez-Boblett,
• Antoine Dupé,
• Zahia Kabouche,
• Christian Bruneau and
• Cédric Fischmeister

Beilstein J. Org. Chem. 2015, 11, 1876–1880, doi:10.3762/bjoc.11.201

• by intramolecular trans-esterification from 6, 7 and 8, as well as cyclic amines by intramolecular cyclization involving primary amine resulting from hydrogenation of the nitrile functionality in 5. All these aspects will be further developed in our group. Cross metathesis of 1 with methyl acrylate

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• prepared from the corresponding allylic alcohol 63 by esterification with the anhydride 64 derived from cyclobutene. Later, the ester 65, on treatment with the catalyst 1 under toluene reflux conditions followed by treatment with the catalyst 2 furnished the macrolide-butenolides 66 in 42–48% yields via