Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents

• Hisato Shimizu,
• Akira Yoshimura,
• Keiichi Noguchi,
• Victor N. Nemykin,
• Viktor V. Zhdankin and
• Akio Saito

Beilstein J. Org. Chem. 2018, 14, 531–536, doi:10.3762/bjoc.14.39

• X-ray analysis [24]. Next, we investigated the oxidative cycloaddition reactions of hydroxamic acids 1a–c with various dienes 2 under the optimal conditions (Table 2). Similarly to the benzoyl derivative 1a, the carbamate analogues 1b (R1 = OBn) and 1c (R1 = Ot-Bu) reacted with 1,3-cyclohexadiene

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

• nucleic acids (PNAs), a lipophilic triphenylphosphonium (TPP) cation was attached to the N-terminal extremity of a PNA through a biodegradable carbamate linker containing a disulfide bridge (Scheme 4B) [20]. It was shown that such PNA conjugates entered cells rapidly and efficiently. Furthermore, a 16-mer

Synthesis and biological evaluation of RGD and isoDGR peptidomimetic-α-amanitin conjugates for tumor-targeting

• Lizeth Bodero,
• Paula López Rivas,
• Barbara Korsak,
• Torsten Hechler,
• Andreas Pahl,
• Christoph Müller,
• Daniela Arosio,
• Luca Pignataro,
• Cesare Gennari and
• Umberto Piarulli

Beilstein J. Org. Chem. 2018, 14, 407–415, doi:10.3762/bjoc.14.29

• group (-CH2NH2) as a handle for conjugation to cytotoxic drugs (Figure 2, ligands 2 and 4) [28][29][30]. Conjugates of the functionalized ligands 2 and 4 with paclitaxel (PTX) via a 2’-carbamate with a self-immolative spacer and the lysosomally cleavable Val-Ala linker [31] were synthesized (Figure 2

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• -diethylaminophosphepane (N,N-diethyl-1,5-dihydro-2,3,4-benzodioxaphosphepin-3-amine) in the presence of 1H-tetrazole followed by in situ oxidation with m-chloroperoxybenzoic acid (m-CPBA) to give fully protected 4’-phosphate 2. The azido group in 2 was reduced, the resulting amine was converted to the N-Fmoc carbamate

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• tetraoxaadamantanes. Inward-pointing isocyanate, urethane and carbamate groups in bisdioxines. The diisocyanate is obtained by Curtius and Hofmann rearrangements of the diazides and diamides [38][39]. Microwave-assisted tetraoxaadamantane formation. Cyclic bisdioxine ester derivative 34 forming a single mono

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

• Yaochun Xu,
• Isabelle Correia,
• Tap Ha-Duong,
• Nadjib Kihal,
• Jean-Louis Soulier,
• Julia Kaffy,
• Benoît Crousse,
• Olivier Lequin and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276

• 271 K (300 ms mixing time), proving that the two forms interconvert in a slow exchange regime on the 1H NMR time scale. This equilibrium was ascribed to the existence of the syn- and anti-rotamers of the carbamate group. The more stable forms (about 85% population at 271 K) were assigned to anti

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• = 75:25). Further modifications (removal of the sulfinyl group and the silyl protecting group in acidic conditions, transformation of the amine in methyl carbamate and oxidation of the primary alcohol into the corresponding carboxylic acid) gave the final isostere 93. In 2013, Pannecoucke and co

Fluorination of some highly functionalized cycloalkanes: chemoselectivity and substrate dependence

• Attila Márió Remete,
• Melinda Nonn,
• Santos Fustero,
• Matti Haukka,
• Ferenc Fülöp and
• Loránd Kiss

Beilstein J. Org. Chem. 2017, 13, 2364–2371, doi:10.3762/bjoc.13.233

• the carbamate N-atom (Scheme 3). Again, only the selective transformation of the C-3 hydroxy group with the fluorinating agent took place, without the involvement of the C-4 OH group. Unfortunately, all further attempted fluorinations of hydroxylated aziridine (±)-7 under various conditions using for

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

• process to stabilize the carbocation species. This method was proved to be efficient by performing the reaction at 9.7 mmol scale to obtain 84% yield of the product. C–O bond formation reaction Carbon–oxygen (C–O) bonds are widely present in molecules containing ester, carbamate and amino acid, etc. [88

• dialkyl carbonates [90]. Mechanochemical transesterification reaction using basic Al2O3 [91]. Mechanochemical carbamate synthesis [92]. Mechanochemical bromination reaction using NaBr and oxone [96]. Mechanochemical aryl halogenation reactions using NaX and oxone [97]. Mechanochemical halogenation

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

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

• -intermediate [76]. After conversion to amide 28 and thioamide 29 the thiazole 31 was obtained by condensation with bromoester 30. The carbamate was then introduced by activation of the deprotected hydroxy group with carbonyldiimidazole and treatment with methylamine, before the ester was selectively reduced to

• the both epimers were oxidized to the ketone by DMP followed by reduction with L-selectride. Protection of the free alcohol with acetate and deprotection of the TES group was then required to install the carbamate with CDI and MeNH2. After deprotection, fragment 75 was synthesized in 67% yield over 2

Regioselective (thio)carbamoylation of 2,7-di-tert-butylpyrene at the 1-position with iso(thio)cyanates

• Anna Wrona-Piotrowicz,
• Marzena Witalewska,
• Janusz Zakrzewski and
• Anna Makal

Beilstein J. Org. Chem. 2017, 13, 1032–1038, doi:10.3762/bjoc.13.102

• -butylpyrene-1-carbonothioyl)carbamate (3o). Yellow solid. Mp 97–98 °C; 1H NMR (600 MHz, CDCl3) δ 9.82 (s, 1H), 8.33 (s, 1H), 8.19 (d, J = 13.2 Hz, 2H), 8.05 (s, 2H), 7.99 (m, 2H), 3.92 (q, J = 7.2 Hz, 2H), 1.74 (m, 9H), 1.59 (m, 9H), 0.97 (t, J = 7.2 Hz, 3H); 13C NMR (150 MHz, CDCl3) δ 211.0, 149.0, 148.9

• : C, 75.34; H, 7.18; N, 3.21, S, 7.14. Diethyl (2,7-di-tert-butyl.pyrene-1,8-dicarbonothioyl)carbamate (4). Yellow solid. Mp 240–241 °C; 1H NMR (600 MHz, CDCl3) δ 9.75 (s, 1H), 9.72 (s, 1H), 8.28 (m, 2H), 8.02 (s, 2H), 7.95 (s, 2H), 3.90 (m, 4H), 1.69 (m, 18H), 0.97 (m, 3H), 0.88 (m, 3H). The 13C NMR

Exploring endoperoxides as a new entry for the synthesis of branched azasugars

• Svenja Domeyer,
• Mark Bjerregaard,
• Henrik Johansson and
• Daniel Sejer Pedersen

Beilstein J. Org. Chem. 2017, 13, 644–647, doi:10.3762/bjoc.13.63

• desired aldehyde 8 was observed. Presumably the problems encountered with compound 4 originates from the ability of the carbamate nitrogen to form a five-membered hydroxypyrrolidine that can undergo further oxidation [19]. Oxidation of alcohol 5 to give aldehyde 9 was accomplished in a low yield using

Transition-metal-catalyzed synthesis of phenols and aryl thiols

• Yajun Liu,
• Shasha Liu and
• Yan Xiao

Beilstein J. Org. Chem. 2017, 13, 589–611, doi:10.3762/bjoc.13.58

• directing groups including azo, amide, anilide, carbamate and unsymmetrical urea, could also promote the ortho-hydroxylation of arenes. Remarkably, 1,4-dioxane not only served as the solvent, but also played an indispensable role in the oxidation of the palladium complex by generating hydroxyl radicals

• Ackermann group used another ruthenium catalyst, [RuCl2(p-cymene)]2 and developed a hydroxylation protocol for carbamates [77]. The hydroxylation occurred in DCE in the presence of PhI(OTFA)2 (Scheme 47). In intermolecular competition experiments, among amide, carbamate and ester, amide showed the highest

Solid-phase enrichment and analysis of electrophilic natural products

• Frank Wesche,
• Yue He and
• Helge B. Bode

Beilstein J. Org. Chem. 2017, 13, 405–409, doi:10.3762/bjoc.13.43

• after azidation and azide enrichment. The tR of 1 is indicated in the crude extract. After enrichment, one distinct peak at 8.1 min corresponding to 3 is visible. (B) The characteristic MS2 fragmentation pattern of the derivatized azide 3 is shown highlighting the neutral loss of carbamate (−121) and

Continuous N-alkylation reactions of amino alcohols using γ-Al₂O₃ and supercritical CO₂: unexpected formation of cyclic ureas and urethanes by reaction with CO₂

• Emilia S. Streng,
• Darren S. Lee,
• Michael W. George and
• Martyn Poliakoff

Beilstein J. Org. Chem. 2017, 13, 329–337, doi:10.3762/bjoc.13.36

• of CO2 into the product. In this case, incorporation presumably occurs via the formation of a carbamate intermediate. This surprising formation of 13 suggests the incorporation of CO2 into 12 with the dimer formation as a competing reaction. In fact, when further conditions were studied, it became

• CO2 (entries 4–6).a Cyclisation and N-alkylation of 1 with different alcohols.a Reactions of ethanolamine.a Showing the effect of conditions on the reaction of diethanolamine 12 to form carbamate 13 and piperazine 14.a Supporting Information Supporting Information File 62: Experimental data

A new class of organogelators based on triphenylmethyl derivatives of primary alcohols: hydrophobic interactions alone can mediate gelation

• Wangkhem P. Singh and
• Rajkumar S. Singh

Beilstein J. Org. Chem. 2017, 13, 138–149, doi:10.3762/bjoc.13.17

• coordination, ionic, hydrophobic forces, etc.) into the gelator molecular structure and studying their gelation behaviour. H-bonding interaction (present in amide, urea, carbamate linkages, etc) alone or in combination with other interactions is the most extensively used strategy in the design of gelators [23

Solution-phase automated synthesis of an α-amino aldehyde as a versatile intermediate

• Hisashi Masui,
• Sae Yosugi,
• Shinichiro Fuse and
• Takashi Takahashi

Beilstein J. Org. Chem. 2017, 13, 106–110, doi:10.3762/bjoc.13.13

• manually concentrated in vacuo. The obtained residue was purified manually using silica gel column chromatography. Carbamate 2a was obtained in 82% yield. Acetal formation was also demonstrated using ChemKonzert. A solution of substrate 2a in dichloromethane was stirred at 25 °C in the reaction vessel (RF1

Robust C–C bonded porous networks with chemically designed functionalities for improved CO₂ capture from flue gas

• Damien Thirion,
• Joo S. Lee,
• Ercan Özdemir and
• Cafer T. Yavuz

Beilstein J. Org. Chem. 2016, 12, 2274–2279, doi:10.3762/bjoc.12.220

• high regeneration energy and raises the overall cost of the carbon capture operations [12][25]. Dry CO2 uptake is not always meaningful, especially with amine functionalities, as flue gas from power plants contains moisture [26]. When binding to CO2, amines go through either carbamate or carbamic acid

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

• Madhuri Vangala and
• Ganesh P Shinde

Beilstein J. Org. Chem. 2016, 12, 2086–2092, doi:10.3762/bjoc.12.197

• are highly reactive compounds that are usually treated with alcohols or amines to give either a new carbonate or a carbamate-linked compound depending on the nucleophile. In one of our earlier reports, polycarbamate nucleic acids were synthesized from p-nitrophenyl carbonates with amines of nucleic

• ] and the synthesis of carbamate-linked compounds using p-nitrophenyl carbonates, we herein report our results from nucleophilic ring opening reactions of DBU and DBN using p-nitrophenyl carbonates. Results and Discussion In the course of this study, we observed that in the absence of a nucleophile the

• in the solvent, leading to the ring opening and formation of the corresponding caprolactam carbamates (Scheme 1). The structure of 1b was confirmed by 1H and 13C spectroscopy, which showed the characteristic carbamate NH triplet at 5.80 ppm in the 1H NMR spectrum and the expected peaks at 176.6 and

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• crucial. In contrast to 1a and 1b, three coexisting isomeric species were observed with NMR spectroscopy in CDCl3 for tetrahydrobiisoindole “NU-BIPHEP(O)” 1c. This behaviour originates from an increased interconversion barrier between the E/Z isomers of the carbamate N–C(O) unit that is derived from a

• carbamate selector units that are soluble in organic solvents [27][28][29][30]. We prepared cellulose derivative 4 which bears 5-fluoro-2-methylphenylcarbamate binding sites [27] and investigated the formation of diastereomeric adducts with 1b and 3 by 31P{1H} NMR spectroscopy in anhydrous CDCl3

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• , carbamate 138, hexahydrobenzothiophene 140 and benzothiophene 142 were converted to the corresponding bisphosphonates 139, 141 and 143, respectively (Scheme 30). The synthesized heterocyclic bisphosphonates showed anti-inflammatory properties. 3 Knoevenagel-induced domino reactions An efficient method into

NeoPHOX – a structurally tunable ligand system for asymmetric catalysis

• Jaroslav Padevět,
• Marcus G. Schrems,
• Robin Scheil and
• Andreas Pfaltz

Beilstein J. Org. Chem. 2016, 12, 1185–1195, doi:10.3762/bjoc.12.114

• prepared from 3-chloropivaloyl chloride (3) by amide formation and subsequent cyclization with the Burgess reagent (methyl N-(triethylammoniumsulfonyl)carbamate) using standard procedures (Scheme 2). Subsequent nucleophilic substitution with KPP2 in refluxing THF proved to be much faster than the analogous

Gold-catalyzed direct alkynylation of tryptophan in peptides using TIPS-EBX

• Gergely L. Tolnai,
• Jonathan P. Brand and
• Jerome Waser

Beilstein J. Org. Chem. 2016, 12, 745–749, doi:10.3762/bjoc.12.74

• , a carbamate and an amide protecting group. A promising result was obtained with 5 mol % gold chloride as catalyst at room temperature in acetonitrile (Table 1, entry 1). Although the reaction did not go to completion even after two days, the desired C2 alkynylation product 5a was obtained in 44

Antibiotics from predatory bacteria

• Juliane Korp,
• María S. Vela Gurovic and
• Markus Nett

Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58

• manifests in the so-called western side chain, which ranges from 10 (myxopyronin A) up to 18 carbon atoms (corallopyronin B). In contrast, the eastern chain is conserved among all members and features a terminal methyl carbamate moiety. Differences in the architectures of the respective biosynthetic