O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• and 4 in selenofucoside 1. The introduction of a 3,4-O-benzylidene protecting group using benzaldehyde dimethyl acetal under standard conditions was ineffective and degradation was observed by TLC. However, the formation of the 3,4-O-benzylidene acetal could be achieved through in situ evaporation of

Facile synthesis of a 3-deazaadenosine phosphoramidite for RNA solid-phase synthesis

• Elisabeth Mairhofer,
• Elisabeth Fuchs and
• Ronald Micura

Beilstein J. Org. Chem. 2016, 12, 2556–2562, doi:10.3762/bjoc.12.250

• . An authentic reference sample that was synthesized according to the previously established 12-step route was used for direct spectroscopic comparison (see Supporting Information File 1) and additionally confirmed its identity. Then, treatment with N,N-dibutylformamide dimethyl acetal [31] resulted in

• amidine protection of the exocyclic C6-NH2 group. At the same time, the applied excess of the reagent allowed to transiently form the corresponding nucleoside 2’,3’-O-acetal [32], leaving the primary 5’-OH group available for selective tritylation with 4,4’-dimethoxytrityl chloride to give compound 6

• -deazaadenosine (6). Compound 5 (199 mg, 747 µmol) was weighed into a 25 mL two-necked flask and dried in high vacuum for 1 hour. Under an argon atmosphere dry pyridine (5 mL) and N,N-dibutylformamide dimethyl acetal (0.40 mL, 1.74 mmol) were added and stirred for 1.5 h at room temperature. Afterwards, all

Combined experimental and theoretical studies of regio- and stereoselectivity in reactions of β-isoxazolyl- and β-imidazolyl enamines with nitrile oxides

• Ilya V. Efimov,
• Marsel Z. Shafikov,
• Nikolai A. Beliaev,
• Natalia N. Volkova,
• Tetyana V. Beryozkina,
• Wim Dehaen,
• Zhijin Fan,
• Viktoria V. Grishko,
• Gert Lubec,
• Pavel A. Slepukhin and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2016, 12, 2390–2401, doi:10.3762/bjoc.12.233

• from the corresponding 5-methylazoles by reaction with dimethylformamide dimethyl acetal (DMF-DMA) adapting synthetic procedures published earlier [26][27][28][29][30]. Their structures can be unambiguously assigned as the trans-isomers by observing the coupling constant (J = 13.0–13.6 Hz) for the

Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis

• Darcy J. Atkinson,
• Briar J. Naysmith,
• Daniel P. Furkert and
• Margaret A. Brimble

Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226

• ], halogenated [36], acetal [37][38][39], benzoxazole [40], thiobenzoxazole [40], ester and carbonate [41] analogues were synthesised and evaluated for antibacterial activity. Only the semisynthetic derivatives possessing hydrophobic groups on the terminal sugar moiety (green) exhibited comparable antibacterial

Experimental and theoretical investigations into the stability of cyclic aminals

• Edgar Sawatzky,
• Antonios Drakopoulos,
• Martin Rölz,
• Christoph Sotriffer,
• Bernd Engels and
• Michael Decker

Beilstein J. Org. Chem. 2016, 12, 2280–2292, doi:10.3762/bjoc.12.221

• ; Introduction The aminal system (N,N-acetal) is the structurally equivalent analogue of the O,O-acetal. In the literature this moiety is found as a core element in various important structures, for example in the naturally occurring alkaloids tetraponerine T1 to T8 from the venom of the New Guinean ant

Hydroxy-functionalized hyper-cross-linked ultra-microporous organic polymers for selective CO₂ capture at room temperature

• Partha Samanta,
• Priyanshu Chandra and
• Sujit K. Ghosh

Beilstein J. Org. Chem. 2016, 12, 1981–1986, doi:10.3762/bjoc.12.185

• dimethyl acetal (FDA) as the cross linker [25][26][27]. Here, aromatic small organic compounds are used to polymerise via C–C cross coupling to produce the targeted porous and physicochemical stable organic hyper-cross-linked polymeric materials. One huge advantage of this material is the low-cost

• synthesis, the cost-effective formaldehyde dimethyl acetal (FDA), FeCl3 and that organic small molecules can produce very low cost materials with high yield [28]. Hyper-cross-linking prevents the close packing of polymeric chains in this type of material to impart the intrinsic porosity. Hyper-cross-linked

TMSBr-mediated solvent- and work-up-free synthesis of α-2-deoxyglycosides from glycals

• Mei-Yuan Hsu,
• Yi-Pei Liu,
• Sarah Lam,
• Su-Ching Lin and
• Cheng-Chung Wang

Beilstein J. Org. Chem. 2016, 12, 1758–1764, doi:10.3762/bjoc.12.164

• dithiol acetal side product 9. Inspired by the results obtained in the synthesis of S-2-deoxyglycosides, we explored the use of numerous alcohols as acceptors in order to directly synthesize O-2-deoxyglycosides from glycals. In Table 2 the reaction of glucal 1 and benzyl alcohol (12) under similar

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• 105a–g with performic acid generated in situ provides a new route to dicarboxylic acids 106a–g and hydroxycarboxylic acids 107a–g (Table 8) [286]. The proposed mechanism of the oxidation of acetal 105f is shown in Scheme 34. In the first step of the reaction, the elimination of methanol from 105f and

• peroxyacetate 138 (Scheme 41) [295]. Later on, the Criegee rearrangement was extended [296] to peroxides 139, 142, and 145 which made it possible to selectively synthesize both cyclic 140, 141, 144 and acyclic enol esters 146 and acetal 143 (Scheme 42). The Criegee rearrangement of 1-hydroperoxy-2

One-pot synthesis of 4′-alkyl-4-cyanobiaryls on the basis of the terephthalonitrile dianion and neutral aromatic nitrile cross-coupling

• Roman Yu. Peshkov,
• Elena V. Panteleeva,
• Wang Chunyan,
• Evgeny V. Tretyakov and
• Vitalij D. Shteingarts

Beilstein J. Org. Chem. 2016, 12, 1577–1584, doi:10.3762/bjoc.12.153

• yield in the reaction with acetal 6f is probably due to the latter’s lower reactivity compared to other alkylating reagents, what was indicated by increased yield of dicyanobiphenyl 4 (14% vs 5% formed in reactions with 6b–e). To demonstrate the effects of varying the aromatic moiety, a set of aromatic

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• ’-oxoaverantin (101) into averufin (102) by intramolecular acetal formation [87]. To date, it is not clear, how exactly the OAVN cyclase participates in this process [88]. Interestingly, the OAVN cyclase operates cofactor-free, although it contains a NAD(P)+-binding Rossman fold. Furthermore, this enzyme is also

Microwave-assisted synthesis of (aminomethylene)bisphosphine oxides and (aminomethylene)bisphosphonates by a three-component condensation

• Erika Bálint,
• Ádám Tajti,
• Anna Dzielak,
• Gerhard Hägele and
• György Keglevich

Beilstein J. Org. Chem. 2016, 12, 1493–1502, doi:10.3762/bjoc.12.146

• predominance over the phosphite in the reaction, the pathway A is more likely, but if the phosphite is used in excess, the pathway B comes to the fore. There are other possibilities to synthesize (aminomethylene)bisphosphonates, such as by the reaction of dimethylformamide diethyl acetal with diethyl phosphite

• )bisphosphonates, but they are much less studied. Only a few publications were found, which focus on their synthesis [33][39][40][41][42], however, a three-component condensation has not been described. They can also be prepared starting from dimethylformamide dimethyl acetal, as in the synthesis of

Discovery of an inhibitor of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells

• Bernardas Morkunas,
• Balint Gal,
• Warren R. J. D. Galloway,
• James T. Hodgkinson,
• Brett M. Ibbeson,
• Yaw Sing Tan,
• Martin Welch and
• David R. Spring

Beilstein J. Org. Chem. 2016, 12, 1428–1433, doi:10.3762/bjoc.12.137

• route towards these derivatives involves coupling of 2 with aromatic amines to generate the corresponding amides, followed by acetal group removal under acidic conditions (Scheme 1) [9]. However, when the product of the reaction of 2 with 3 was treated with TFA, compound 4 was generated (Scheme 1). The

Copper-catalyzed [3 + 2] cycloaddition of (phenylethynyl)di-p-tolylstibane with organic azides

• Mizuki Yamada,
• Mio Matsumura,
• Yuki Uchida,
• Masatoshi Kawahata,
• Yuki Murata,
• Naoki Kakusawa,
• Kentaro Yamaguchi and
• Shuji Yasuike

Beilstein J. Org. Chem. 2016, 12, 1309–1313, doi:10.3762/bjoc.12.123

• excellent yields. In the case of the reaction with o-bromobenzyl azide, the carbon–bromine bond of 3b remained intact, and other byproducts were not observed. Azides containing a linear alkyl group, acetal moiety, and a heteroaromatic ring such as pyridine gave the corresponding triazoles 3i–k in moderate

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• under the standard reaction conditions. The tosyl and 2,4,6-triisopropylbenzenesulfonyl groups on nitrogen can be removed after protection of the ketone as the cyclic acetal by using sodium naphthalide in THF (Scheme 6). After protection, the diphenylphosphoramidate group can also be removed with

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• notable that the intramolecular C–H bond insertion to form the bridged polycycle was significantly faster than an intermolecular insertion into the MOM acetal methylene, which would be electronically activated by the two flanking oxygen substituents. Later, Magnus showed that a conformationally flexible

A cross-metathesis approach to novel pantothenamide derivatives

• Jinming Guan,
• Matthew Hachey,
• Lekha Puri,
• Vanessa Howieson,
• Kevin J. Saliba and
• Karine Auclair

Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95

• -methoxybenzaldehyde acetal protecting group in 9 is believed to tie back the alcohols and prevent them from coordinating and deactivating the ruthenium catalyst. When testing the scope of the metathesis reaction with 9, a variety of partners were chosen, including not only acrylic acid (10a), but also 2-vinylpyridine

• 14, which was directly coupled to the carboxylic acid to yield 15. Finally, the desired compound 16 was obtained after acid deprotection of the p-methoxybenzaldehyde acetal in a 90% aqueous acetic acid solution (84% yield). Biological studies The antimicrobial activity of 16 was investigated. No

One-pot synthesis of enantiomerically pure N-protected allylic amines from N-protected α-amino esters

• Gastón Silveira-Dorta,
• Sergio J. Álvarez-Méndez,
• Víctor S. Martín and
• José M. Padrón

Beilstein J. Org. Chem. 2016, 12, 957–962, doi:10.3762/bjoc.12.94

• forming the appropriate aluminoxy acetal, which is expected to be stable enough at temperatures as low as −78 °C. This is partly corroborated by the decomposition of the aluminoxy acetal to the over reduced alcohol when 1.4 equiv of DIBAL-H were used (Table 1, entries 1, 3 and 5) [24]. The presence of an

• aluminoxy acetal is also supported when THF is used, although the yields are low, probably due to the destabilization of the aluminoxy acetal (Table 1, entry 4) [25]. Once established the reaction conditions, we next studied the scope and limitations of the one-pot protocol using a small subset of assorted

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

• ] of 14 followed by azidolysis [41] furnished 15. 2-Azido-3,4-epoxide 18 was prepared from readily available [42] 2,3-isopropylidene-D-mannosan (16) in five steps (Scheme 2). Tosylation of 16 [43], followed by hydrolysis of the benzylidene acetal [44] and oxirane ring closure [45] at C-4 delivered 1,6

• acetal with acetic anhydride gave a mixture containing 1,2-oxazoline 41 as the main product (Scheme 5). The structure of oxazoline 41 was confirmed by single crystal X-ray diffraction analysis which also confirmed the retention of configuration during the preceding fluorine introduction. To prevent

• to furnish acetylated 3-fluoro-GalNAc 6 isolated as a separable mixture of anomers. The D-galacto configuration of 6 is manifested by the lower 3JH3,H4 coupling value (3.4 Hz, α-anomer) in comparison with that of its C-4 epimer 5 (8.6 Hz, α-anomer). Acetolysis of the internal acetal in 26 proceeded

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• aromatic macrocycle [25]. Interestingly, as these hosts are tetra-acetals we initially tried removing the template under acidic conditions. However, even reflux in 1:1 EtOH/H2SO4 for a week failed to affect the starting material. Evidently, under reversible conditions, a broken acetal can easily reform

• before the other three are themselves cleaved. An irreversible acetal cleavage mechanism is therefore key to success. Meanwhile, because our chiral canyons project required some new, tripodal zinc-binding ligands for templating a collagen helix, the whole endeavor had itself become very syntheses

Three new trixane glycosides obtained from the leaves of Jungia sellowii Less. using centrifugal partition chromatography

• Luíse Azevedo,
• Larissa Faqueti,
• Marina Kritsanida,
• Antonia Efstathiou,
• Despina Smirlis,
• Gilberto C. Franchi Jr,
• Grégory Genta-Jouve,
• Sylvie Michel,
• Louis P. Sandjo,
• Raphaël Grougnet and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2016, 12, 674–683, doi:10.3762/bjoc.12.68

• oxymethine groups, the hemi-acetal and one of the CH2O (δ 3.65, 3.83/63.0) groups. Furthermore, the quaternary carbons included an α,β-unsaturated carbonyl (δ 165.5), an olefinic carbon (δ 137.5) and two sp3 carbons (δ 47.7 and 53.8). Fifteen carbon shifts remained after the sugar deduction suggesting the

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

• , obtained via Au-catalyzed Meyer–Schuster rearrangement. Assembly of 5-oxygenated bisindolylpentenones. DMB: 3,4-dimethoxybenzyl, DMFDMA: N,N-dimethylformaldehyde dimethyl acetal. Benzylic oxidation as side reaction of DMB removal. Hydroxyalkylation of N-protected indoles with β-cyclocitral and SnCl4

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• rate-determining one and that the [1,9]-H shift is the one with the lowest energy barrier. Keywords: acetal; benzindenes; DFT calculations; fulvene; hydrogen shift; Introduction Fulvenes (also known as pentafulvenes), [1][2][3][4] a unique class of trienes, have intrigued chemists for decades due to

• wondered whether acetalic functions could be employed as internal H donors in intramolecular hydride-like shifts, analogous to that highlighted in Scheme 1, toward fulvene frameworks. With this goal in mind we designed the unknown acetal-fulvenes 3 (Scheme 2) as potential candidates for assaying the [1,4

• Experimental study The starting acetal-fulvenes 3 were prepared by the condensation of substituted 2-(1,3-dioxolan-2-yl)benzaldehydes 4 with cyclopentadiene following a well-established synthetic methodology [33]. With the aim of promoting the desired hydride transfer by thermal activation, we first heated the

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• alkynylations in good yields and ee’s. In 2011, we reported the first example of enantioselective alkynylation of a cyclic oxocarbenium ion intermediate (Scheme 15) [55]. Isochroman oxocarbenium ion 41 was formed in situ via Lewis acid-mediated ionization of a racemic acetal precursor. By using a Cu(MeCN)4PF6

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• benzylic bromination followed by elongation of the C3 unit [22]. To this end, the ester group at the C1 position of 15 was reduced by lithium borohydride, and the resultant 1,3-diol protected to give acetal 16 [16]. After various experiments, selective bromination of the methyl group on the aromatic ring

• % yield (dr > 10:1) via the method established in Scheme 3. After derivatization to acetal 22 in 2 steps, we then turned our attention to the introduction of the C4 ester substituents. Amongst various different conditions investigated – including Pd-catalyzed coupling reactions – a halogen-lithium

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• example, disulfide [10], acetal [11], imine [12] and boronates [13][14][15][16], to allow the generation of new covalent structures under thermodynamic control. Complete esterification is observed for boronate esters bearing ortho-amines [17]. The conceptual advantage compared to traditional irreversible