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

Synthesis of five- and six-membered cyclic organic peroxides: Key transformations into peroxide ring-retaining products

• Alexander O. Terent'ev,
• Dmitry A. Borisov,
• Vera A. Vil’ and
• Valery M. Dembitsky

Beilstein J. Org. Chem. 2014, 10, 34–114, doi:10.3762/bjoc.10.6

• 2,6-dimethyl-6-(phenylsulfonylmethyl)-7,8-dioxabicyclo[3.3.1]nonan-2-ol (296) followed by the isolation of the isomer (6R)-2,6-dimethyl-6-(phenylsulfonylmethyl)-7,8-dioxabicyclo[3.3.1]nonan-2-ol (296a) and benzylation of the latter to obtain the target peroxide 297a (Scheme 84) [107]. Methyl 2-(6

Triol-promoted activation of C–F bonds: Amination of benzylic fluorides under highly concentrated conditions mediated by 1,1,1-tris(hydroxymethyl)propane

• Pier Alexandre Champagne,
• Alexandre Saint-Martin,
• Mélina Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2013, 9, 2451–2456, doi:10.3762/bjoc.9.283

• selectivity was observed for N-benzylation (Table 3, entries 4 and 10). The reaction also tolerates simple electronic variations on the benzylic fluoride, as the 4-phenyl group can be exchanged for a 4-bromo (Table 3, entries 5–7), 4-tert-butyl (Table 3, entries 8–10) or 3-methoxy group (Table 3, entry 11

Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

• Quynh Pham Bao Nguyen and
• Taek Hyeon Kim

Beilstein J. Org. Chem. 2013, 9, 2113–2119, doi:10.3762/bjoc.9.248

• (Supporting Information File 1). Polymers 5 were also highly soluble in THF, CH2Cl2, and DMF and insoluble in methanol and water, which allowed the implementation of solvent extraction techniques commonly used in classical organic synthesis. Next, asymmetric benzylation, as a model alkylation reaction with

• responsible for the poor de value [17], and Merrifield resin was an unsuitable support [14]. In contrast, the asymmetric benzylation in the soluble polymer 5a gave excellent diastereoselectivity (>99% de) which was not affected by the base or reaction time (Table 2, entries 2–5). Interestingly, although

• . Synthesis of NCPS-supported N-acylated 2-imidazolidinone chiral auxiliaries 5. Synthesis of non-crosslinked chloromethylated polystyrenes 4. Optimization of asymmetric benzylation reaction. Diastereoselective alkylations before TFA cleavage. Synthesis of chiral acids 8 and recycling of polymer 3

Diastereoselective radical addition to γ-alkyl-α-methylene-γ-butyrolactams and the synthesis of a chiral pyroglutamic acid derivative

• Tomoko Yajima,
• Eriko Yoshida and
• Masako Hamano

Beilstein J. Org. Chem. 2013, 9, 1432–1436, doi:10.3762/bjoc.9.161

• . The N-pivaloyl group on 11 was converted to the Boc group, because ruthenium oxidation did not proceed on using the pivaloyl-protected substrate 11. The phenyl group was oxidized to the carboxylic acid by using ruthenium trichloride [15][16], and the benzylation of the carboxyl group yielded the

Exploration of an epoxidation–ring-opening strategy for the synthesis of lyconadin A and discovery of an unexpected Payne rearrangement

• Brad M. Loertscher,
• Yu Zhang and
• Steven L. Castle

Beilstein J. Org. Chem. 2013, 9, 1179–1184, doi:10.3762/bjoc.9.132

• stereocenter of 13 was assigned based on the established stereochemical course of the Myers alkylation [23]. Finally, reductive removal of the chiral auxiliary with lithium amidotrihydroborate [26] produced alcohol 14, and benzylation yielded triether 15. Asymmetric epoxidation of alkene 15 was somewhat

A new synthetic access to 2-N-(glycosyl)thiosemicarbazides from 3-N-(glycosyl)oxadiazolinethiones and the regioselectivity of the glycosylation of their oxadiazolinethione precursors

• El Sayed H. El Ashry,
• El Sayed H. El Tamany,
• Mohy El Din Abdel Fattah,
• Mohamed R. E. Aly,
• Ahmed T. A. Boraei and
• Axel Duerkop

Beilstein J. Org. Chem. 2013, 9, 135–146, doi:10.3762/bjoc.9.16

• analytical data were identical with those of the aminolysis product (Scheme 4). For ultimate confirmation of the structures of S- and N-glycosides 5–10, the benzylation of the indole was chosen, because these derivatives can serve to prove the glycosyl rearrangement and glycosyl TSC formation. Moreover

• the methylene carbon at δC 48.4–48.8 ppm in the 13C NMR spectra support a successful benzylation. Additional NMR signals of the phenyl protons and carbon atoms of the phenyl ring were another strong evidence for the N-benzylation of the indole units. The different (yet large) values of the coupling

• of 30. Packing diagram of 30. Structures of the different glycosylthiosemicarbazides. Glycosylations of oxadiazolinethione. Synthesis of glycosylthiosemicarbazides by solvolysis. Solvolysis of glycosylsulfanyloxadiazoles. Benzylation of the S- and N-glycosides 5–10. Aminolysis of benzylated indolyl-3

Acylsulfonamide safety-catch linker: promise and limitations for solid–phase oligosaccharide synthesis

• Jian Yin,
• Steffen Eller,
• Mayeul Collot and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2012, 8, 2067–2071, doi:10.3762/bjoc.8.232

• benzylation and deprotection to afford 24 prior to treatment with sodium methoxide (Scheme 4). Surprisingly, linker 7 was again isolated as the major product as determined by TLC and NMR, indicating that the nucleophilicity or basicity of NaOMe was responsible for cleavage. Other reagents, such as aqueous