Efficient routes toward the synthesis of the D-rhamno-trisaccharide related to the A-band polysaccharide of Pseudomonas aeruginosa

• Aritra Chaudhury,
• Sajal K. Maity and
• Rina Ghosh

Beilstein J. Org. Chem. 2014, 10, 1488–1494, doi:10.3762/bjoc.10.153

• summarized in Scheme 1. Accordingly, compounds 2 and 3b [42] were obtained uneventfully from 1a in 92% and 75%, respectively (Scheme 1). All attempts to place an acetyl protection at the O-2 position of 1b with high yield failed. The poor yield was presumed to be due to the migration of the 2-O-acetyl group

• to the O-3 position leading to a mixture which was hard to separate. Hence we switched to O-benzoyl protection which was found to be less susceptible to migration [25]. The 2-O-benzoylated compound 4 was prepared by conversion of 1b into its corresponding methyl 2,3-orthobenzoate derivative followed

• triisopropylsilanethiol (TIPST) under reflux in octane over 2–3 h [30] in overall 74% and 64% yields, respectively, over two steps. It is worth noting here that during column chromatographic purification after AcOH-mediated cleavage of the orthobenzoate derivative some losses were incurred due to the migration of the 2-O

Human dendritic cell activation induced by a permannosylated dendron containing an antigenic GM₃-lactone mimetic

• Renato Ribeiro-Viana,
• Elena Bonechi,
• Javier Rojo,
• Clara Ballerini,
• Giuseppina Comito,
• Barbara Richichi and
• Cristina Nativi

Beilstein J. Org. Chem. 2014, 10, 1317–1324, doi:10.3762/bjoc.10.133

• (Figure 1) was able to elicit in vivo antimelanoma antibodies [32]. More recently [33], we established that the multivalent presentation of this synthetic mimetic positively interferes with human melanoma cell (A375) adhesion, migration and resistance to apoptosis, showing a clear amplification of the

Tandem Cu-catalyzed ketenimine formation and intramolecular nucleophile capture: Synthesis of 1,2-dihydro-2-iminoquinolines from 1-(o-acetamidophenyl)propargyl alcohols

• Gadi Ranjith Kumar,
• Yalla Kiran Kumar,
• Ruchir Kant and
• Maddi Sridhar Reddy

Beilstein J. Org. Chem. 2014, 10, 1255–1260, doi:10.3762/bjoc.10.125

• distance. When we treated 3 with similar reaction conditions (TsN3, 10 mol % CuI, 1.2 equiv K2CO3, 0.1 M CH3CN) as used in the previous method, surprisingly, only α,β-unsaturated amide 5 was obtained as a single product through acetyl migration on the intermediate 4. No trace of product through acetamide

Amino acid motifs in natural products: synthesis of O-acylated derivatives of (2S,3S)-3-hydroxyleucine

• Oliver Ries,
• Martin Büschleb,
• Markus Granitzka,
• Dietmar Stalke and
• Christian Ducho

Beilstein J. Org. Chem. 2014, 10, 1135–1142, doi:10.3762/bjoc.10.113

• and Grignard addition. The enantiomeric purity of reisolated 3 was determined by HPLC analysis as its racemization can readily occur via silyl migration under the basic reaction conditions (see Supporting Information File 2 for HPLC chromatograms and for the synthesis of the racemic reference). After

• -Fmoc-protected building blocks potentially suitable for solid-phase peptide synthesis (SPPS). It is well established that O-acylated β-hydroxy-α-amino acids can be used in Fmoc-strategy peptide syntheses without migration of the acyl unit [37][38][39]. Based on these findings, we have desired to

Olefin cross metathesis based de novo synthesis of a partially protected L-amicetose and a fully protected L-cinerulose derivative

• Bernd Schmidt and
• Sylvia Hauke

Beilstein J. Org. Chem. 2014, 10, 1023–1031, doi:10.3762/bjoc.10.102

• furanose 17. Facile migration of carboxylates upon TBAF-mediated desilylation of a vicinal alcohol has previously been observed by us in a different context [68]. We assume that this process starts with a nucleophilic attack of the alkoxylate 18 at the ester carbon, giving a five membered intermediate 19

Regioselective S_N2' Mitsunobu reaction of Morita–Baylis–Hillman alcohols: A facile and stereoselective synthesis of α-alkylidene-β-hydrazino acid derivatives

• Silong Xu,
• Jian Shang,
• Junjie Zhang and
• Yuhai Tang

Beilstein J. Org. Chem. 2014, 10, 990–995, doi:10.3762/bjoc.10.98

• azodicarboxylates 2 generates the Huisgen zwitterion intermediate 8 [37][38]. Subsequent proton transfer and phosphonium migration between 8 and the MBH alcohol 1 produce an oxophosphonium intermediate 9 and a hydrazine anionic species 10 [36]. Finally, an expedient SN2' attack of species 10 on 9, probably

Aza-Diels–Alder reaction between N-aryl-1-oxo-1H-isoindolium ions and tert-enamides: Steric effects on reaction outcome

• Amitabh Jha,
• Ting-Yi Chou,
• Zainab ALJaroudi,
• Bobby D. Ellis and
• T. Stanley Cameron

Beilstein J. Org. Chem. 2014, 10, 848–857, doi:10.3762/bjoc.10.81

• ]. The reaction of 2-chloroquinoline with 2-formylphenylboronic acid yielded tetracyclic isoindoloquinoline using Suzuki cross-coupling conditions where the C–C bond formation is followed by nucleophilic attack of the pyridine lone pair on the neighbouring aldehyde and proton migration [21]. Several

Polyglycerol-functionalized nanodiamond as a platform for gene delivery: Derivatization, characterization, and hybridization with DNA

• Li Zhao,
• Yuki Nakae,
• Hongmei Qin,
• Tadamasa Ito,
• Takahide Kimura,
• Hideto Kojima,
• Lawrence Chan and
• Naoki Komatsu

Beilstein J. Org. Chem. 2014, 10, 707–713, doi:10.3762/bjoc.10.64

• (20 mg/mL), b) ND-PG-Arg8, c) ND-PG-Lys8 and d) ND-PG-His8 (b–d, 1.0 mg/mL) in water. Electrophoretic migration of pDNA, NP (ND50-PG or ND-PG-BPP), and NP/pDNA mixtures at various weight ratios. Synthetic route from ND50 to ND-PG-BPP; i) glycidol, 140 °C, 20 h; ii) p-TsCl, pyridine, 0 °C to rt; iii

Isocyanide-based multicomponent reactions towards cyclic constrained peptidomimetics

• Gijs Koopmanschap,
• Eelco Ruijter and
• Romano V.A. Orru

Beilstein J. Org. Chem. 2014, 10, 544–598, doi:10.3762/bjoc.10.50

• peptidomimetic design, the incorporation of N-protected aldehydes 4 (Scheme 2) is of great importance since deprotection of the α-adduct 5 allows acyl-migration and give access to α-hydroxy-β-amino amide derivatives 7 that possess important biological properties. This Passerini–amine deprotection–acyl migration

• , yielding pyrrazol-3-ones 107. The authors assumed that the cyclization proceeds via an N–C acyl migration of the trifluoroacetyl group, based on the labile character of the latter moiety (Scheme 33). In contrast, acid-promoted cyclization cleaved the trifluoroacetyl group and revealed the initially

An oxidative amidation and heterocyclization approach for the synthesis of β-carbolines and dihydroeudistomin Y

• Suresh Babu Meruva,
• Akula Raghunadh,
• Raghavendra Rao Kamaraju,
• U. K. Syam Kumar and
• P. K. Dubey

Beilstein J. Org. Chem. 2014, 10, 471–480, doi:10.3762/bjoc.10.45

• . Based on the reaction conditions 8 can be obtained from 20 after aqueous work-up or at higher temperature heating, 20 undergoes a sequential prototropic migration leading to the formation of 2,9-dihydro-β-carboline derivative 7. To the best of our knowledge, this is a novel method for the synthesis of 1

Efficient carbon-Ferrier rearrangement on glycals mediated by ceric ammonium nitrate: Application to the synthesis of 2-deoxy-2-amino-C-glycoside

• Alafia A. Ansari,
• Y. Suman Reddy and
• Yashwant D. Vankar

Beilstein J. Org. Chem. 2014, 10, 300–306, doi:10.3762/bjoc.10.27

• mechanism The proposed mechanism of the formation of the C-allyl glycosides is shown in Scheme 1. The ring oxygen could donate an electron to the Ce3+ leading to the formation of a radical cation A. Subsequent migration of the double bond and loss of the acetyl radical could result in the formation of the

Substrate dependent reaction channels of the Wolff–Kishner reduction reaction: A theoretical study

• Shinichi Yamabe,
• Guixiang Zeng,
• Wei Guan and
• Shigeyoshi Sakaki

Beilstein J. Org. Chem. 2014, 10, 259–270, doi:10.3762/bjoc.10.21

• propane product concertedly. From the (1-phenyl)ethyl substituted diimine, a carbanion intermediate is formed. The para carbon of the phenyl ring of the anion is subject to the protonation, which leads to a 3-ethylidene-1,4-cyclohexadiene intermediate. Its [1,5]-hydrogen migration gives the ethylbenzene

Synthesis of the B-seco limonoid core scaffold

• Hanna Bruss,
• Hannah Schuster,
• Rémi Martinez,
• Markus Kaiser,
• Andrey P. Antonchick and
• Herbert Waldmann

Beilstein J. Org. Chem. 2014, 10, 194–208, doi:10.3762/bjoc.10.15

• free hydroxy groups as MOM ethers, which was accompanied by silyl migration, the synthesis of rearrangement precursor 66 was completed. Application of the developed reaction conditions for the rearrangement of the model systems was fruitless, resulting in only cleavage of the ester moiety. Crucial for

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• formation gives rise to either cis- or trans-divinylcyclopropanes 268/271. cis-Divinylcyclopropane 271 can readily undergo DVCPR to give bicycle 272. 1,2-Migration of the migrating group G leads to final bicycle 273 after regeneration of the catalyst. Trans-divinylcyclopropane 268 can undergo DVCPR after

• 1,2-migration and subsequent formation of cis-divinylcyclopropane 269 yielding bridged bicycle 270. Chung and coworkers [210] discovered a related reaction pattern using platinum(II) as the catalyst. Depending on the attached rests on enyne 276 both possible cycloheptadienes (bridged 277 or annulated

Continuous-flow Heck synthesis of 4-methoxybiphenyl and methyl 4-methoxycinnamate in supercritical carbon dioxide expanded solvent solutions

• Phei Li Lau,
• Ray W. K. Allen and
• Peter Styring

Beilstein J. Org. Chem. 2013, 9, 2886–2897, doi:10.3762/bjoc.9.325

• can be formed under kinetic control. The third possibility is the geminal or branched (b) isomer which is usually formed where a cationic intermediate forms that facilitates migration of the σ-Pd–C bond from the terminal alkenic 1-position to the 2-position. In the majority of publications, the

Triphenylene discotic liquid crystal trimers synthesized by Co₂(CO)₈-catalyzed terminal alkyne [2 + 2 + 2] cycloaddition

• Bin Han,
• Ping Hu,
• Bi-Qin Wang,
• Carl Redshaw and
• Ke-Qing Zhao

Beilstein J. Org. Chem. 2013, 9, 2852–2861, doi:10.3762/bjoc.9.321

• view angles [1][2]. More interestingly, DLCs can self-organize into columnar mesophases with a high degree of order, and show fast unidirectional charge migration properties, and have been studied as soft organic semiconductors [3][4][5][6][7][8][9][10][11][12]. Solution-processed and ink-jet printing

An efficient method for the construction of polysubstituted 4-pyridones via self-condensation of β-keto amides mediated by P₂O₅ and catalyzed by zinc bromide

• Liquan Tan,
• Peng Zhou,
• Cui Chen and
• Weibing Liu

Beilstein J. Org. Chem. 2013, 9, 2681–2687, doi:10.3762/bjoc.9.304

• , when R is aryl, a 1,3-acyl migration occurred from N to C of intermediate 6 [35][36][37][38][39], and affords imine 7 and its equilibrium compound 8, the subsequent intramolecular nucleophilic cyclization of intermediate 8 provides the final product 4-pyridones [20][38]. Alternatively, when R is

• aliphatic, the 1,3-acyl migration is not observed – maybe the migration leads to an unstable imine intermediate. Therefore, under the acidic conditions, a cationic species 10 is generated from the intermediate 6 and the subsequent intramolecular dehydration process provides 2-pyridones 11 [19]. Conclusion

• In summary, we have established an improved efficient synthetic protocol for the synthesis of 4-pyridone derivatives by a sequence of intermolecular dehydration of β-keto amides in the presence of phosphorus pentoxide (P2O5), 1,3-acyl migration and intramolecular dehydration. Comparing to the similar

New developments in gold-catalyzed manipulation of inactivated alkenes

• Michel Chiarucci and
• Marco Bandini

Beilstein J. Org. Chem. 2013, 9, 2586–2614, doi:10.3762/bjoc.9.294

• /AgClO4] (5/15 mol %) furnished corresponding functionalized pyrrolidines in good yields and moderate stereoselectivity (Scheme 22) [58]. The preferred alkene activation versus allenes was recently observed in the cascade 1,3-migration/[2 + 2] cycloaddition of 1,7-enyne benzoates (Scheme 23) [59]. When 83

• with enantiopure substrates. The proposed mechanism proceeded through 3,3-migration of the propargylic ester to form the allenoate 87. The expected activation of the allene was probably unfavoured for steric reasons, therefore gold activation of the alkene moiety triggered attack of the more

• with simple ketones. Proposed reaction mechanism for the intramolecular [Au(I)]-catalyzed hydroalkylation of alkenes with ketones. Tandem Michael addition/hydroalkylation catalyzed by [Au(I)] and [Ag(I)] salts. Intramolecular [Au(I)]-catalyzed tandem migration/[2 + 2] cycloaddition of 1,7-enyne

Oxidative 3,3,3-trifluoropropylation of arylaldehydes

• Akari Ikeda,
• Masaaki Omote,
• Shiho Nomura,
• Miyuu Tanaka,
• Atsushi Tarui,
• Kazuyuki Sato and
• Akira Ando

Beilstein J. Org. Chem. 2013, 9, 2417–2421, doi:10.3762/bjoc.9.279

• migration of the benzylic proton of 4 in the basic medium. To confirm the hypothesis, we conducted the reaction by using benzaldehyde-d to clarify whether or not proton migration was involved in the reaction sequence. When benzaldehyde-d was treated with 1 and CsF in DMF at 80 °C, the reaction gave a

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• a nucleophilic intramolecular attack of the carboxy moiety on the activated alkyne. 1,2-Migration of the ester affording a gold–carbene of type A is usually preferred when a terminal alkyne is used [38][39][40]. Based on this concept, several groups have shown that the resulting carbenoid

• could be formally categorized as a [2 + 1] cycloaddition. In particular, they showed that it is possible to trap the intermediate gold–carbenes resulting from a 1,2-acyloxy migration in propargyl esters such as 1, with external alkenes (e.g. vinylarenes), to give cyclopropane products [41]. The racemic

• be formally considered as a [4 + 3] annulation. A possible mechanism would involve a gold-mediated 1,2-acyloxy migration of the propargyl ester to generate a gold–carbene species III which cyclopropanates a C–C double bond of the diene to form a cis-cyclopropane intermediate IV. A subsequent gold

Synthesis of enantiomerically pure N-(2,3-dihydroxypropyl)arylamides via oxidative esterification

• Akula Raghunadh,
• Satish S More,
• T. Krishna Chaitanya,
• Yadla Sateesh Kumar,
• Suresh Babu Meruva,
• L. Vaikunta Rao and
• U. K. Syam Kumar

Beilstein J. Org. Chem. 2013, 9, 2129–2136, doi:10.3762/bjoc.9.250

• was attempted with both methylamine and ammonia solution. During the deprotection of (S)-3-(1,3-dioxoisoindolin-2-yl)-2-hydroxypropyl benzylate, we observed the migration of the benzoyl group from the hydroxy group to the amino group (Scheme 4). 6a was isolated after column chromatographic

Gold(I)-catalyzed hydroarylation reaction of aryl (3-iodoprop-2-yn-1-yl) ethers: synthesis of 3-iodo-2H-chromene derivatives

• Pablo Morán-Poladura,
• Eduardo Rubio and
• José M. González

Beilstein J. Org. Chem. 2013, 9, 2120–2128, doi:10.3762/bjoc.9.249

• accomplish a reaction manifold earlier recognized in the synthesis of regioisomeric halogenated phenanthrenes, but they are using two different metals [45]. Catalytic cycloisomerization reactions of heteroatom-substituted alkynes that take place without heteroatom migration are known [46][47][48]. On this

• this context, switching from NTs to O as the linker is, intrinsically, a demanding process attempting to access 3-iodo-2H-chromene cores, as migration is less favorable for more electron-donating groups. So, the application of this cyclization and concomitant iodine migration strategy to synthesize the

• outlined in Table 1 entry 7 were chosen to broach the potential of this 1,2-iodine migration–hydroarylation process using different iodinated propargyl aryl ethers. The results are summarized in Table 2. Interestingly, as no further additives are required, heating the corresponding aryl propargyl ether in

The chemistry of isoindole natural products

• Klaus Speck and
• Thomas Magauer

Beilstein J. Org. Chem. 2013, 9, 2048–2078, doi:10.3762/bjoc.9.243

• described for the biogenesis of (S)-reticuline (101) (compare Scheme 11). A de-aromatizing spirocyclization of 121 leads to (R)-orientalinone (122), which, after reduction of the ketone to the secondary alcohol 123, undergoes a [1,2]-alkyl migration with concomitant loss of water. Re-aromatization and

Gold-catalyzed regioselective oxidation of propargylic carboxylates: a reliable access to α-carboxy-α,β-unsaturated ketones/aldehydes

• Kegong Ji,
• Jonathan Nelson and
• Liming Zhang

Beilstein J. Org. Chem. 2013, 9, 1925–1930, doi:10.3762/bjoc.9.227

• excellent regioselectivity, which is ascribed to inductive polarization of the C–C triple bond by the electron-withdrawing carboxy group. The gold carbene intermediates thus generated undergo selective 1,2-acyloxy migration over a 1,2-C–H insertion, and the selectivities could be dramatically improved by

• rationalized as the results of divergent transformations of the α-oxo gold carbene B: the former is formed via a two-step 2,3-acetoxy migration [22][23], and the latter most likely via a concerted carbene 1,2-C–H insertion[2]. The selective formation of the Z isomer of 5a-OAc can be attributed to that B adopts

• Scheme 3 (the top half). Instead of initially undergoing oxidative gold carbene formation, a gold-promoted 1,2-acetoxy migration [25] would generate a vinyl gold carbene intermediate (i.e., C), which can then be oxidized by 3 to yield the product. However, this scenario is deemed unlikely by the