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

• a nucleophilic trifluoromethylation reaction of Ruppert’s reagent on the (R)-Garner’s aldehyde 5 in THF and in the presence of a catalytic amount of TBAF. Benzylation of the alcohol of 6 was then performed to obtain the desired intermediate as two diastereoisomers 7a and 7b that were easily

• in good yield starting from the N-benzylation of L-proline in the presence of KOH, then activation of the carboxylic acid functionality of 10 using SOCl2 at low temperature, followed by condensation with 2-aminobenzophenone (Scheme 2). Complexation of 11 with nickel nitrate and glycine under basic

The photodecarboxylative addition of carboxylates to phthalimides as a key-step in the synthesis of biologically active 3-arylmethylene-2,3-dihydro-1H-isoindolin-1-ones

• Ommid Anamimoghadam,
• Saira Mumtaz,
• Anke Nietsch,
• Gaetano Saya,
• Cherie A. Motti,
• Jun Wang,
• Peter C. Junk,
• Ashfaq Mahmood Qureshi and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2017, 13, 2833–2841, doi:10.3762/bjoc.13.275

• substitution between 1c and phenylacetate (2a) to phthalimide 6. Ester 6 was indeed obtained in 37% yield by gently heating a mixture of phthalimide 1c and phenylacetate (2a) in acetone/water. Subsequently, compound 5 was independently prepared by photodecarboxylative benzylation of 6 for 4 h in 91% yield

Synthesis of ergostane-type brassinosteroids with modifications in ring A

• Vladimir N. Zhabinskii,
• Darya A. Osiyuk,
• Yuri V. Ermolovich,
• Natalia M. Chaschina,
• Tatsiana S. Dalidovich,
• Miroslav Strnad and
• Vladimir A. Khripach

Beilstein J. Org. Chem. 2017, 13, 2326–2331, doi:10.3762/bjoc.13.229

• selective benzylation of its equatorial hydroxy group [14] followed by chlorochromate oxidation gave, after removal of the benzyl protecting group in 26, the diketone 27. Its reduction proceeded regio- and stereoselectively to afford the 2α,3β-diol 28. Finally, treatment of this compound with KOH in MeOH

• proceeded regioselectively at the diol group of the side chain and gave, after benzylation at position 2, the alcohol 36 (Scheme 8). The oxidation of the latter product afforded compound 37, which after deprotection, delivered the desired 3-dehydro-24-epicastasterone (38). Conclusion In conclusion, we have

Conjugated nitrosoalkenes as Michael acceptors in carbon–carbon bond forming reactions: a review and perspective

• Yaroslav D. Boyko,
• Valentin S. Dorokhov,
• Alexey Yu. Sukhorukov and
• Sema L. Ioffe

Beilstein J. Org. Chem. 2017, 13, 2214–2234, doi:10.3762/bjoc.13.220

• -bromooxime 26 with lithium enolate 27 to give oxime 28 via the Michael addition to transient nitrosoalkene NSA6 [31]. Oxime adduct 28 existed predominantly in a cyclic 1,2-oxazine form (Scheme 11). Subsequent benzylation of oxime 28 and the thermal retro-[2 + 2]/[4 + 2]-cycloaddition cascade followed by

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions

• Daily Rodríguez-Padrón,
• Alina M. Balu,
• Antonio A. Romero and
• Rafael Luque

Beilstein J. Org. Chem. 2017, 13, 1982–1993, doi:10.3762/bjoc.13.194

• ]. Regarding the acid-catalyzed processes, aromatic alkylation reactions are among the most versatile and widely investigated reactions which can grant access to a wide range of compounds as important intermediates, fragrances, agrochemicals and pharmaceuticals [47][48][49]. In this sense, the benzylation of

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

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• -linker, the Friedel–Crafts cross-linking polymerization is promoted smoothly by anhydrous FeCl3 in dry 1,2-dichloroethane (DCE). The monomers were either commercially available (Sug-1) or prepared (Sug-2 and Sug-3) by benzylation of free sugars with benzyl bromide and sodium hydride. The chemical

Cyclodextrins tethered with oligolactides – green synthesis and structural assessment

• Cristian Peptu,
• Mihaela Balan-Porcarasu,
• Alena Šišková,
• Ľudovít Škultéty and
• Jaroslav Mosnáček

Beilstein J. Org. Chem. 2017, 13, 779–792, doi:10.3762/bjoc.13.77

• -containing polymers while simplifying the complexity induced by multifunctional initiator through partial benzylation of the β-CD resulting in a CD-diol. Also, the ROP of D,L-LA catalyzed by 4-dimethylaminopyridine and initiated by all 21 OH groups of β-CD was employed by Xu et al. [15]. However, the above

Total synthesis of a Streptococcus pneumoniae serotype 12F CPS repeating unit hexasaccharide

• Peter H. Seeberger,
• Claney L. Pereira and
• Subramanian Govindan

Beilstein J. Org. Chem. 2017, 13, 164–173, doi:10.3762/bjoc.13.19

• blocks 10 and 7 [27] in a dichloromethane–ether (enables alpha selectivity) mixture in 56% yield (Scheme 4). Removal of the silyl ether and benzylidene groups of 19 yielded triol 20 before benzylation afforded disaccharide thioglycoside building block 21. Activation of disaccharide 21 resulted in the

Orthogonal protection of saccharide polyols through solvent-free one-pot sequences based on regioselective silylations

• Serena Traboni,
• Emiliano Bedini and
• Alfonso Iadonisi

Beilstein J. Org. Chem. 2016, 12, 2748–2756, doi:10.3762/bjoc.12.271

• activation effect of boron complexes [33]. Over the last years, we have addressed our interest towards the development of solvent-free protocols aimed at regioselective protection of highly functionalized saccharide substrates. This effort led to a simple protocol for the selective benzylation of primary

• saccharide alcohols [34], the first catalytic tin-mediated procedure for regioselective benzylation/allylation of hydroxy groups incorporated into vicinal diols [35], and three alternative acetalation protocols [36]. Besides the avoided use of solvents, these approaches appear advantageous owing to their

• previously performed better than pyridine in the tin-catalyzed solvent-free regioselective benzylation or allylation of sugars [35]. The silylation rate was not appreciably influenced by tin catalysis (compare entries 2 and 3 in Table 1), although a previous report described the stoichiometric use of

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

• ] (Scheme 2). Selective protection of the C5 primary hydroxy group as PMP ether using p-methoxyphenol under Mitsunobu reaction conditions afforded 4 that on benzylation of the C3 hydroxy group (NaH and benzyl bromide in DMF) gave compound 5. Upjohn dihydroxylation of 5 using K2OsO4·2H2O followed by

Synthesis and in vitro cytotoxicity of acetylated 3-fluoro, 4-fluoro and 3,4-difluoro analogs of D-glucosamine and D-galactosamine

• Štěpán Horník,
• Lucie Červenková Šťastná,
• Petra Cuřínová,
• Jan Sýkora,
• Kateřina Káňová,
• Roman Hrstka,
• Ivana Císařová,
• Martin Dračínský and
• Jindřich Karban

Beilstein J. Org. Chem. 2016, 12, 750–759, doi:10.3762/bjoc.12.75

• reduction, oxidative debenzylation [24] was applied instead of the more common hydrogenation. Debenzylation of 10 gave dianhydro derivative 13 [34][37] (available also directly from D-glucal [31][33] or from levoglucosan [38]) which was converted to 14 by Latrell–Dax inversion at C-4 [39]. O-Benzylation [40

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• Chancellor and coworkers [42], gave nitrophenol 11 in a reasonable yield (45%). The Batcho–Leimgruber protocol failed for nitrophenol 11 [43]. However, after O-benzylation of 11 to 12, Boc-indole 15 was obtained in the very good yield of 91%. Coupling with TMS-acetylene was followed by desilylation to obtain

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• by a regioselective substitution at C-2, followed by a C-3 benzylation to access compound 49. As the other regioisomer 52 could not be obtained so easily, additional protection–deprotection steps were required. Efficiency of compounds 26a–f and 27a–c against chemical warfare agents: Preliminary tests

Spiro-fused carbohydrate oxazoline ligands: Synthesis and application as enantio-discrimination agents in asymmetric allylic alkylation

• Jochen Kraft,
• Martin Golkowski and
• Thomas Ziegler

Beilstein J. Org. Chem. 2016, 12, 166–171, doi:10.3762/bjoc.12.18

• benzylation, fully characterized and subjected to palladium catalyzed Suzuki–Miyaura coupling with 2-pyridineboronic acid N-phenyldiethanolamine ester to give the corresponding 2-pyridyl spiro-oxazoline (PyOx) ligands. The spiro-oxazoline ligands showed high asymmetric induction (up to 93% ee) when applied as

• , anomers could easily be separated by chromatography after benzylation of 5 and 6 with BnBr and NaH to give the corresponding benzylated sulfanyloxazolines 7 and 8 which were air and moisture stable (see Supporting Information File 1 for full experimental details). Nevertheless, it should be noted that

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

• alkylation of nitroalkanes with alkyl halides. aNaOt-Bu as base, hexanes as solvent. Scope of the copper-catalyzed nitroalkane benzylation. Application of the nitro-alkylation reaction to the synthesis of phentermine. Possible mechanism of the thermal redox process. Scope of the reaction of nitroalkanes with

• -directed synthesis of Z-alkenes. Scope of the phenol-directed Z-alkene synthesis. Rationale for the formal [3 + 2] cycloaddition. Scope of the formal [3 + 2] cycloaddition. Benzylation of styrenes using copper catalysis. Copper-catalyzed carboiodination of alkynes. Copper-catalyzed trans-carbohalogenation

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• a key step. The L,L-cyclodi(iodotryrosin) (131) was subjected to a benzylation reaction to give the protected compound 132 (76%). A one-pot Pd-catalyzed borylation and Suzuki–Miyaura coupling was employed to generate the cross-coupling product 134 (42%). Finally, deprotection of 134 was carried out

Synthesis of icariin from kaempferol through regioselective methylation and para-Claisen–Cope rearrangement

• Qinggang Mei,
• Chun Wang,
• Zhigang Zhao,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 1220–1225, doi:10.3762/bjoc.11.135

• and Discussion Our synthetic approach to 1 commenced with the preparation of aglycone 3, as illustrated in Scheme 1. First, 7-O-benzylkaempferide (6) was easily obtained from kaempferol through tetraacetylation, followed by benzylation at C-7 and selectively methylation, according to our previously

Selective methylation of kaempferol via benzylation and deacetylation of kaempferol acetates

• Qinggang Mei,
• Chun Wang,
• Weicheng Yuan and
• Guolin Zhang

Beilstein J. Org. Chem. 2015, 11, 288–293, doi:10.3762/bjoc.11.33

• /bjoc.11.33 Abstract A strategy for selective mono-, di- and tri-O-methylation of kaempferol, predominantly on the basis of selective benzylation and controllable deacetylation of kaempferol acetates, was developed. From the selective deacetylation and benzylation of kaempferol tetraacetate (1), 3,4′,5

• . Keywords: benzylation; deacetylation; kaempferol; methylation; regioselectivity; Introduction Kaempferol [2-(4-hydroxyphenyl)-3,5,7-trihydroxychromen-4-one] (Figure 1) and its derivatives are widely distributed in plants such as beans, broccoli, strawberries, teas, and propolis [1][2]. They are well known

• biological activity evaluation of flavonoids [21][22], we report here a convenient and efficient method for mono-, di- and tri-O-methylation of kaempferol, by taking the advantage of the different reactive potential (hydrolysis, benzylation and methylation) of O-acetoxy groups in multi-acetylated kaempferol

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Synthesis of modified cyclic and acyclic dextrins and comparison of their complexation ability

• Kata Tuza,
• László Jicsinszky,
• Tamás Sohajda,
• István Puskás and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2014, 10, 2836–2843, doi:10.3762/bjoc.10.301

• synthetic route was worked out via bromination, benzylation, deacetylation and debenzylation to obtain the 2-hydroxypropyl maltooligomer counterparts. The complexation properties of non-modified and modified cyclic and acyclic dextrins were studied and compared by photon correlation spectroscopy (PCS) and

• elucidation of the O-benzyl intermediary products and the final HP-maltooligomers was performed by NMR (see Supporting Information File 1). Both proton and carbon assignments are based on the DEPT-ed-HSQC spectra. The NMR spectra confirm the complete 1-O-benzylation at the glycosidic oxygen (Figures S1–S6

• chloroform/acetone for bromination, 85:15 v/v alcohol free chloroform:acetone for benzylation and 10:7 v/v dioxane:satd. aq ammonia for hydroxypropylation and debenzylation; visualization: 15% cc. H2SO4 in 96% EtOH. Synthesis of HP-maltooligomers 1-Bromo-peracetyl-maltooligomers, according to [14

Synthesis of 2-substituted tryptophans via a C3- to C2-alkyl migration

• Michele Mari,
• Simone Lucarini,
• Francesca Bartoccini,
• Giovanni Piersanti and
• Gilberto Spadoni

Beilstein J. Org. Chem. 2014, 10, 1991–1998, doi:10.3762/bjoc.10.207

• attributed to the greater migratory aptitude of both the p-methoxy- and p-chlorobenzyl groups, compared to the p-nitrobenzyl substituent (even though in this case a detrimental coordination between nitro group and Lewis acid can occur), thus agreeing with earlier studies on the benzylation of indoles [46

Expedient synthesis of 1,6-anhydro-α-D-galactofuranose, a useful intermediate for glycobiological tools

• Luciana Baldoni and
• Carla Marino

Beilstein J. Org. Chem. 2014, 10, 1651–1656, doi:10.3762/bjoc.10.172

• synthesis of the 1,6-anhydro derivatives 2 and 12, the key step of which proceeds by a cascade set of three consecutive reactions. The method compares well to existing methods and by avoiding cumbersome steps, such as a benzylation and several column chromatography purifications, is an effective approach

Synthesis of a sucrose dimer with enone tether; a study on its functionalization

• Zbigniew Pakulski,
• Norbert Gajda,
• Magdalena Jawiczuk,
• Jadwiga Frelek,
• Piotr Cmoch and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2014, 10, 1246–1254, doi:10.3762/bjoc.10.124

• . Benzylation of 11. To a solution of alcohol 11 (82 mg, 0.037 mmol) in DMF (1 mL), sodium hydride (60% suspension in mineral oil, 7 mg) was added and the mixture was stirred for 30 min at rt. Benzyl bromide (11 μL, 0.092 mmol) was added, and stirring was continued overnight. Excess of sodium hydride was

Concise, stereodivergent and highly stereoselective synthesis of cis- and trans-2-substituted 3-hydroxypiperidines – development of a phosphite-driven cyclodehydration

• Peter H. Huy,
• Julia C. Westphal and
• Ari M. P. Koskinen

Beilstein J. Org. Chem. 2014, 10, 369–383, doi:10.3762/bjoc.10.35

• , phenylalanine, phenylglycine and methionine 1a–d were converted to their N-benzyl-N-carbamate-protected derivatives 2a–d (PG = Cbz, Boc) in a practical one pot procedure through combination of Quitt´s reductive benzylation protocol [61] and a Schotten–Baumann acylation [62][63] in 70–95% yield (Scheme 1). While

• carbamate protected amino acid derivatives 3 (remaining as impurity in the isolated products 2), quantitative benzylation (1→I) was ensured by successive addition of three portions of benzaldehyde/NaBH4 (Quitt´s procedure [61] → two portions) and by maintaining the pH at a value of 10–11. The extractive

• side chain carboxyl function with acetyl chloride in MeOH [70][71][72]. Neutralization of the reaction mixture with K2CO3 and reductive benzylation [73] in one-pot then delivered the benzyl amines 8e and 8f. While glutamic acid showed selective mono esterification after 3 h at room temperature, the