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

Convergent synthesis of the tetrasaccharide repeating unit of the cell wall lipopolysaccharide of Escherichia coli O40

• Abhijit Sau and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2012, 8, 2053–2059, doi:10.3762/bjoc.8.230

• ]; and (f) preparation of β-D-mannosidic moiety from the β-D-glucoside [13]. Benzylation of 2-azidoethyl 3-O-benzyl-4,6-O-benzylidene-β-D-mannopyranoside (2) [13] (prepared from D-glucose in nine steps) by using benzyl bromide and sodium hydroxide [21] followed by reductive ring opening of the 4,6-O

A new approach toward the total synthesis of (+)-batzellaside B

• Jolanta Wierzejska,
• Shin-ichi Motogoe,
• Yuto Makino,
• Tetsuya Sengoku,
• Masaki Takahashi and
• Hidemi Yoda

Beilstein J. Org. Chem. 2012, 8, 1831–1838, doi:10.3762/bjoc.8.210

• -gel column chromatography, 12a-A was subjected to the TBS protection–benzylation sequence, as illustrated for the preparation of 13B, to generate 13A in 50% yield over three steps. In the next step, deprotection of the TBS group with TBAF [37] and subsequent tosylation of the resulting hydroxy group

Studies on the substrate specificity of a GDP-mannose pyrophosphorylase from Salmonella enterica

• Lu Zou,
• Ruixiang Blake Zheng and
• Todd L. Lowary

Beilstein J. Org. Chem. 2012, 8, 1219–1226, doi:10.3762/bjoc.8.136

• methoxide and then tert-butyldiphenylchlorosilane in DMF. Benzylation of 32 using benzyl bromide and sodium hydride gave 33 in 84% yield. The TBDPS group was then cleaved and replaced with a methyl group to give the 6-methoxy compound 35 in 72% yield over two steps. The protected dibenzyl phosphate 36 was

Palladium-catalyzed substitution of (coumarinyl)methyl acetates with C-, N-, and S-nucleophiles

• Kalicharan Chattopadhyay,
• Erik Fenster,
• Alexander J. Grenning and
• Jon A. Tunge

Beilstein J. Org. Chem. 2012, 8, 1200–1207, doi:10.3762/bjoc.8.133

• the biologically active coumarin motif. This new method was utilized to prepare a 128-membered library of aminated coumarins for biological screening. Keywords: benzylation; catalysis; coumarin; chemical diversity; decarboxylative; palladium; substitution; Introduction Coumarins are privileged

• hydroxymethylcoumarins, we chose to investigate their decarboxylative couplings of enolates. We have previously shown that decarboxylative benzylation (DcB) is a useful method for the addition of less-stabilized enolate anions to a benzyl functionality [46][53][54][55]. Thus, we envisioned being able to add various

• ketone enolates to the exo-methyl position of the coumarin core by this method (Table 1). Screening of reaction conditions showed that, in contrast to common decarboxylative benzylation conditions (Table 1,entries 1 and 2) under which nonpolar solvents give the best DcB, the selective mono-alkylation of

Synthesis and antifungal properties of papulacandin derivatives

• Marjolein van der Kaaden,
• Eefjan Breukink and
• Roland J. Pieters

Beilstein J. Org. Chem. 2012, 8, 732–737, doi:10.3762/bjoc.8.82

• aromatic group, i.e., the eventual spiroketal group of the glucose, to be introduced as an aryliodide with an ortho hydroxymethylene as in 12. The commercially available 3,5-dihydroxybenzoic acid (1) was esterified, followed by benzylation of the aromatic hydroxy groups and reduction of the ester to the

Acceptor-influenced and donor-tuned base-promoted glycosylation

• Stephan Boettcher,
• Martin Matwiejuk and
• Joachim Thiem

Beilstein J. Org. Chem. 2012, 8, 413–420, doi:10.3762/bjoc.8.46

• derivatives 22 and 23, a five-step synthesis was performed in each case to obtain the galacto- and glucopyranosyl donors 8 and 9 (Scheme 3). Initially, peracetates 22 and 23 were converted into the thioglycopyranosides 24 and 25 with BF3∙Et2O/thiophenole [7]. Subsequent deacetylation [8] and benzylation [9

Asymmetric synthesis of quaternary aryl amino acid derivatives via a three-component aryne coupling reaction

• Elizabeth P. Jones,
• Peter Jones,
• Andrew J. P. White and
• Anthony G. M. Barrett

Beilstein J. Org. Chem. 2011, 7, 1570–1576, doi:10.3762/bjoc.7.185

• publication, we demonstrated the scope of the methodology over a range of ortho-lithiation benzyne precursors. To establish that any one of these precursors could be used to form quaternary adducts, we subjected the benzylation conditions to precursor 2b and the allylation conditions to precursor 2c

Convergent synthesis of the tetrasaccharide repeating unit of the O-antigen of Shigella boydii type 9

• Abhishek Santra and
• Anup Kumar Misra

Beilstein J. Org. Chem. 2011, 7, 1182–1188, doi:10.3762/bjoc.7.137

• (br s, H-1C), 4.95 (d, J = 3.6 Hz, H-1D) in the 1H NMR and signals at δ 92.8 (C-1D), 81.0 (C-1C) in the 13C NMR spectrum). Compound 6 was transformed into disaccharide thioglycoside donor 7 in 91% yield under a one-pot deacetylation–benzylation reaction condition [22] (Scheme 2). In this case, the

Microphotochemistry: 4,4'-Dimethoxybenzophenone mediated photodecarboxylation reactions involving phthalimides

• Oksana Shvydkiv,
• Kieran Nolan and
• Michael Oelgemöller

Beilstein J. Org. Chem. 2011, 7, 1055–1063, doi:10.3762/bjoc.7.121

• intermolecular reactions). DMBP mediated α-photodecarboxylation of N-phthaloylglycine (1). Photodecarboxylation of potassium phthaloyl-γ-aminobutyrate (3). Photodecarboxylative cyclization of potassium phthalimidomethylsulfanylacetate (6). Photodecarboxylative benzylation of 2. Photodecarboxylative addition of

Synthesis of 6-PEtN-α-D-GalpNAc-(1–>6)-β-D-Galp-(1–>4)-β-D-GlcpNAc-(1–>3)-β-D-Galp-(1–>4)-β-D-Glcp, a Haemophilus influenzae lipopolysacharide structure, and biotin and protein conjugates thereof

• Andreas Sundgren,
• Martina Lahmann and
• Stefan Oscarson

Beilstein J. Org. Chem. 2010, 6, 704–708, doi:10.3762/bjoc.6.80

• thioglycoside 4 [14] yielded the 6-O-silylated compound 5 (92%), benzylation of which gave donor 6 (85%). A benzyl group in the 4-position was preferred to an ester group to avoid the risk of acyl migration during subsequent reactions; desilylation, glycosidation and phosphorylation. 3II,4II-Diols of lactose

A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

• Magnus Rueping and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2010, 6, No. 6, doi:10.3762/bjoc.6.6

• –Crafts conditions using stoichiometric amounts of a Lewis acid, such as AlCl3. With the need for more environmentally and economically benign processes, the Friedel–Crafts-type synthesis of 1,1-diarylalkanes using catalytic amounts of a metal or acid catalyst and more environmental friendly benzylation

• applied. Even fairly unstable thiophene- and furan-2-carbaldehyde derived benzyl alcohols, cyano(phenyl)methyl acetate or 3-hydroxy-3-phenylpropanoates and benzyl methyl ethers have been successfully applied as benzylation reagents [26]. Later, the same authors used gold(III) as a catalyst for an

• 1,1-diarylalkanes The Friedel–Crafts benzylation of arenes using benzyl alcohols was discussed in the previous chapter. Even though it renders a convenient and environmental benign approach to 1,1-diarylalkanes, there is still one stoichiometric side product formed during this transformation, namely

Convenient method for preparing benzyl ethers and esters using 2-benzyloxypyridine

• Susana S. Lopez and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2008, 4, No. 44, doi:10.3762/bjoc.4.44

• -benzyloxypyridine (2), and magnesium oxide in toluene was cooled to 0 °C and treated with methyl triflate. The reaction mixture was allowed to warm to room temperature and then heated at 90 °C for 24 h. Table 1 summarizes the results from the benzylation of a representative group of functionalized alcohols under

• trifluorotoluene, but toluene has a lower dipole moment and also is subject to Friedel–Crafts benzylation under the reaction conditions [6][22]. Trifluorotoluene (also known as benzotrifluoride or BTF) is recommended as a “green” solvent alternative to dichloromethane [23]. Benzylation reactions of N-Boc-serine 3d

• (entry 7, 84%) and methyl lactate (3e, 79%) verify compatibility with esters and carbamates. Note that the benzylation of N-Boc-serine methyl ester (3d) compares favourably to analogous reactions reported previously [24], because the neutral reaction conditions described herein are compatible with the

Single and double stereoselective fluorination of (E)-allylsilanes

• Marcin Sawicki,
• Angela Kwok,
• Matthew Tredwell and
• Véronique Gouverneur

Beilstein J. Org. Chem. 2007, 3, No. 34, doi:10.1186/1860-5397-3-34

• difluorinated alkene 7 (Scheme 4). The key steps necessary to perform this conversion were a dihydroxylation, the reduction of the ester group and the benzylation of the resulting primary alcohol. Preliminary work revealed that the order of steps was important and that protecting group manipulations were

• protection of the diol as an acetonide, the reduction of the ester, the benzylation of the resulting primary alcohol and a final deprotection step. The spectroscopic data of compound 7 were identical to the ones of a sample prepared independently according to the procedure reported by O'Hagan.[31] This

Solvent- controlled regioselective protection of allyl- 4,6-benzylidene glucopyranosides

• Kerry Ann Ness and
• Marie E. Migaud

Beilstein J. Org. Chem. 2007, 3, No. 26, doi:10.1186/1860-5397-3-26

• benzylation of methyl 4,6-O-benzylidene glucopyranoside claim isolated yields ranging from the 37% and below [9] to 75% and above [10]. Others reported multi-step procedures to achieve introduction of a suitable protecting group at the 2-position of the 4,6-O-benzylidene 1-O-alkyl protected glucose [11] or

• used enzymes to achieve selectivity [12]. Results and discussion While preparing the partially protected glucose 1 from α-allyl-4,6-benzylidene glucoside 2 (Scheme 1), we observed that mono-benzylation could be achieved, if instead of DMF and the usual reagents' combination (i.e. NaH, BnBr, Bu4NI), THF

• was to be used as reaction solvent (Scheme 1). Osborn had reported the regioselective mono-acylation/alkylation of the C-3 hydroxyl of 4,6-O-benzylidene-β-D-glycopyranosides using NaH/CuCl2 in THF [6]. Distinctively, we observed the regioselective benzylation at the C-2 position of the 1-O-allyl-α

Investigation of acetyl migrations in furanosides

• O. P. Chevallier and
• M. E. Migaud

Beilstein J. Org. Chem. 2006, 2, No. 14, doi:10.1186/1860-5397-2-14

• base catalysed benzylation of the C-3 hydroxyl and the acid catalysed acetonide removal prior to acetylation at the C-2 position of the methyl arabinoside. While an acid-catalysed benzylation would have significantly shorten the route, it was found to be unsuccessful when carried out on 5-O-TBDPS