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

• reaction for the synthesis of Tris-protected [3.1.0] pyrrolidines, it occurred to us that protecting groups other than Tris may be equally effective for the [3.1.0] system. The Tris group was chosen during our optimization of the six-membered ring system (Table 5), which may have significantly different

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• (Scheme 1) [14]. 3-Allyl-3-hydroxyoxindoles were obtained in 89–98% yield and with 32–86% ee when the reactions were carried out at −60 °C using 5 mol % of CNN pincer Pd complex (cat. 1). Substituents attached to the isatin aromatic ring and N-protecting groups were important in controlling the

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

• is remarkable that this protocol avoids using O-protecting groups or the Garner aldehyde which have been used extensively in the synthesis of related compounds. Conclusion In summary, this simple protocol described herein enables a rapid access to a number of useful enantiopure allylic amines from

Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents

• Daniel Wiegmann,
• Stefan Koppermann,
• Marius Wirth,
• Giuliana Niro,
• Kristin Leyerer and
• Christian Ducho

Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77

• guanidinylation reagent 55. With the protected epicapreomycidine precursor 56 in hand, the Boc and acetonide protecting groups were removed. Urea formation with the valine derivative 57 with final oxidation of the primary hydroxy function afforded the desired dipeptide 58 [78] (Scheme 7). Furthermore, Ducho et al

• (5'S)-configuration, contrary to the results of MIC value determination. Further studies were then carried out with (5'R)-derivatives only, i.e., with 5'-epimers of the parent natural products. The influence of protecting groups was examined applying a strategy of stepwise deprotection. This led to

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

• -anhydrohexopyranoses were then converted into the target fluoro analogs of D-glucosamine and D-galactosamine (Scheme 1). Dual protection of the anomeric and primary hydroxy groups in the form of the 1,6-anhydro bridge reduced the number of protecting groups, and the rigid bicyclic skeleton of 1,6-anhydrohexopyranoses

Iridium/N-heterocyclic carbene-catalyzed C–H borylation of arenes by diisopropylaminoborane

• Mamoru Tobisu,
• Takuya Igarashi and
• Naoto Chatani

Beilstein J. Org. Chem. 2016, 12, 654–661, doi:10.3762/bjoc.12.65

• derivatives by treatment with protecting groups in a one-pot reaction sequence. The reactivity of 1g has previously been well-exploited in catalytic borylation of aryl halides [22][23][24][25][26][27]. Herein, we report the C–H borylation of arenes using 1g catalyzed by an Ir/N-heterocyclic carbene (NHC

• ) complex bearing an ICy ligand was the most efficient catalyst. The initially formed aminoborylated products can readily be converted to the corresponding organoboron compounds bearing various boron-protecting groups. Experimental Procedure for the Ir-catalyzed borylation of heteroarenes using 1g In a

Studies on the synthesis of peptides containing dehydrovaline and dehydroisoleucine based on copper-mediated enamide formation

• Franziska Gille and
• Andreas Kirschning

Beilstein J. Org. Chem. 2016, 12, 564–570, doi:10.3762/bjoc.12.55

• total synthesis when the guanidine group has either to be liberated by the removal of the protecting groups or used for the introduction to the corresponding ornithine residue. These results demonstrate that the copper-mediated cross-coupling reaction depends on the functional groups present in the

• peptide containing the vinyl iodide moiety and on the chosen protecting groups. Vinyl iodides bearing an arginine moiety gave a significantly reduced yield of the desired cross-coupling product compared to the corresponding ornithine derivatives. Furthermore, it turned out that the Alloc and Pbf

• protecting groups are not compatible for this enamide forming protocol. The best results were obtained by using the Boc-protected amide 30 and ornithine-containing vinyl iodides 24 and 28 (Scheme 5). It needs to be noted that the presence of a Cbz protecting group in dehydrooligopeptides is problematic

A selective and mild glycosylation method of natural phenolic alcohols

• Mária Mastihubová and
• Monika Poláková

Beilstein J. Org. Chem. 2016, 12, 524–530, doi:10.3762/bjoc.12.51

• Acetyl-protecting groups are the simplest choice also for the protection of the glycone part since the deprotection of both, sugar and aromatic moieties, can be accomplished in one step. Naturally occurring O-glycosides possess mostly 1,2-trans-glycosidic linkages. Therefore, neighbouring group

Diastereoselective synthesis of new O-alkylated and C-branched inositols and their corresponding fluoro analogues

• Charlotte Collet,
• Françoise Chrétien,
• Yves Chapleur and
• Sandrine Lamandé-Langle

Beilstein J. Org. Chem. 2016, 12, 353–361, doi:10.3762/bjoc.12.39

• case of the O-alkylated inositols a three carbon arm was envisioned whereas for the C-branched derivatives two and three carbon atom arms were used. For the fluorinated inositols, we developed a synthetic route with easily removing protecting groups, as acetates, suitable for PET imaging application

• the access to myo-10 and scyllo-10 in 78% and 75% yield, respectively. The O-alkylated inositol derivatives myo-1 and scyllo-1 were obtained quantitatively by removing of the benzyl protecting groups of compounds myo-10 and scyllo-10 by hydrogenation under pressure [45] using palladium hydroxide as

• and 92% yield, respectively [48]. All protecting groups of myo-13 and scyllo-13 were removed by the treatment with Na0 in MeOH [49], which gave quantitatively the fully deprotected fluorinated O-alkylated inositols myo-2 and scyllo-2. Synthesis of C-branched myo- and scyllo-inositol derivatives

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

• the use of Boc-protecting groups. Reduction of 6-iodoindole with NaBH3CN in HOAc afforded 6-iodoindoline (38, 90%) [47], which was subsequently TIPS-protected (39, Scheme 6). Hydroxyalkylation of 39 with β-cyclocitral (30) gave cyclization precursor 40 (68%). We were pleased to find that this time the

Application of 7-azaisatins in enantioselective Morita–Baylis–Hillman reaction

• Qing He,
• Gu Zhan,
• Wei Du and
• Ying-Chun Chen

Beilstein J. Org. Chem. 2016, 12, 309–313, doi:10.3762/bjoc.12.33

• enantioselectivity was observed for products 3h and 3i (Table 2, entries 8 and 9). 7-Azaisatins with different N-protecting groups were also applied to the MBH reaction with N-phenylmaleimide (2a), including methoxymethyl (MOM), benzyl (Bn) and 4-chlorophenyl substituents. All of them showed a lower reactivity and

Amino-functionalized (meth)acryl polymers by use of a solvent-polarity sensitive protecting group (Br-t-BOC)

• Helmut Ritter,
• Monir Tabatabai and
• Markus Herrmann

Beilstein J. Org. Chem. 2016, 12, 245–252, doi:10.3762/bjoc.12.26

• )acrylates [2]. Therefore, for the synthesis of amino-containing (meth)acrylic monomers and polymers suitable amino-protecting groups are required. Classical protecting groups such as ammonium salts, F-MOC, Z- or t-BOC, respectively are readily available. Regarding to this aspect, we published some papers

• about polymer protecting groups about three decades ago [3][4][5][6][7]. However, they are limited in application by certain restrictions on the deprotection conditions. Therefore, there is a continued interest in developing new protecting groups which can be cleaved by different mechanisms. Keeping

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

• , particularly for iminium ions, progress is on-going to determine stable precursors to the requisite iminium ion intermediates and to identify readily removed protecting groups. Given the potential of enantioselective, copper-catalyzed alkynylations to deliver important scaffolds, significant effort is still

Synthesis of cyclic N¹-pentylinosine phosphate, a new structurally reduced cADPR analogue with calcium-mobilizing activity on PC12 cells

• Ahmed Mahal,
• Stefano D’Errico,
• Nicola Borbone,
• Brunella Pinto,
• Agnese Secondo,
• Valeria Costantino,
• Valentina Tedeschi,
• Giorgia Oliviero,
• Vincenzo Piccialli and
• Gennaro Piccialli

Beilstein J. Org. Chem. 2015, 11, 2689–2695, doi:10.3762/bjoc.11.289

• allowed the removal of both the OCE phosphate protecting groups together with the acetate function, thus obtaining the key intermediate 18 as triethylammonium salt after HPLC purification. The derivate 18, dissolved in DMF at the final concentration of 2 mM was treated with EDC (1.2 equiv) and the

Selectively fluorinated cyclohexane building blocks: Derivatives of carbonylated all-cis-3-phenyl-1,2,4,5-tetrafluorocyclohexane

• Mohammed Salah Ayoup,
• David B. Cordes,
• Alexandra M. Z. Slawin and
• David O'Hagan

Beilstein J. Org. Chem. 2015, 11, 2671–2676, doi:10.3762/bjoc.11.287

• demonstrated that 4 can be elaborated in a relatively straightforward manner by mainstream reactions of electrophilic aromatic substitution [7]. This extended to the synthesis of cyclohexane substituted (S)-L-phenylalanines with orthogonal protecting groups suitable for their incorporation into peptides [8

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• -membered carbocycle was realized via a B-alkyl Suzuki–Miyaura cross-coupling reaction. Optimization studies of this key ring closure with different protecting groups on the lactol functionality revealed methyl acetal 135 as the most efficient substrate for this transformation. The challenging key step was

Versatile synthesis and biological evaluation of novel 3’-fluorinated purine nucleosides

• Hang Ren,
• Haoyun An,
• Paul J. Hatala,
• William C. Stevens Jr,
• Jingchao Tao and
• Baicheng He

Beilstein J. Org. Chem. 2015, 11, 2509–2520, doi:10.3762/bjoc.11.272

• % yield after protecting group manipulation from arabinoguanosine [34]. Complicated orthogonally protected adenosine and guanosine derivatives with three or four different protecting groups have also been used for the synthesis of compounds 2 and 23, and the protocols required extensive manipulation of

• the protecting groups [35]. Compound 2 has also been synthesized starting from xylofuranoside by manipulating the protecting groups on the carbohydrate moiety [36]. De Clercq and co-workers [37] developed a protocol for the synthesis of 3’-fluororibofuranose in 10 steps, and it requires epoxide

• provide the desired protected key intermediate 26 in 90% yield (Scheme 1). To construct the first series of fluorinated purine analogues, compound 26 was treated with a saturated solution of ammonia in methanol, which resulted in the amination at the 6-position and deprotection of the protecting groups to

Synthesis of D-fructose-derived spirocyclic 2-substituted-2-oxazoline ribosides

• Madhuri Vangala and
• Ganesh P. Shinde

Beilstein J. Org. Chem. 2015, 11, 2289–2296, doi:10.3762/bjoc.11.249

• therapeutics [11][12][13]. Traditionally, oxazolines are used as protecting groups in organic synthesis [14]. Several efficient methods for the construction of the 2-oxazoline functionality are reported in the literature from alkenes, carboxylic acid derivatives, nitriles [15][16][17][18][19], etc. In

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• outcome of the RRM process depends on the selection of the protecting groups, reaction conditions, and electronic properties of substrates involved. Oligomerization is a common side reaction in the RRM and external olefins such as ethylene prevents unwanted oligomerization processes. For earlier work

SmI₂-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B

• Nils Marsch,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184

• dichlorobenzene at 150 °C to obtain a 3:5 mixture of the tricyclic cyclopentanones 17 and 18 (Scheme 4) [34]. Almost no regioselectivity between the 5- and 7-positions was observed. Our ongoing studies investigate the influence of bulky N-protecting groups. In the absence of the α,β-double bond, SmI2 in THF did

Synthesis of alpha-tetrasubstituted triazoles by copper-catalyzed silyl deprotection/azide cycloaddition

• Zachary L. Palchak,
• Paula T. Nguyen and
• Catharine H. Larsen

Beilstein J. Org. Chem. 2015, 11, 1425–1433, doi:10.3762/bjoc.11.154

• ketimine is followed by stoichiometric alkynylation with a trimethylsilyl-protected alkynyllithium reagent. Removal of the silyl and sulfinyl protecting groups allows for CuAAC with a resin-bound azide. Acylation of the amine followed by dehydration yields the active alpha-tetrasubstituted triazole [7

Synthesis and evaluation of the biostability and cell compatibility of novel conjugates of nucleobase, peptidic epitope, and saccharide

• Dan Yuan,
• Xuewen Du,
• Junfeng Shi,
• Ning Zhou,
• Abdulgader Ahmed Baoum,
• Khalid Omar Al Footy,
• Khadija Omar Badahdah and
• Bing Xu

Beilstein J. Org. Chem. 2015, 11, 1352–1359, doi:10.3762/bjoc.11.145

• chain from the resin with 95% trifluoroacetic acid (TFA) without N-protecting groups. Later, NAS was obtained by reacting D-glucosamine hydrochloride with the fully protected NA. After cleaving the protecting group on amino acids with 95% TFA, we used reversed-phase high-performance liquid

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• to the N-arylation of MPTTFs and BPTTFs using a variety of aryl halides. Keywords: heterocycles; protecting groups; sulfur chemistry; tetrathiafulvalene; Ullman coupling; Introduction Tetrathiafulvalene (TTF) derivatives are of considerable interest in the fields of supramolecular chemistry and

• a common, protected MPTTF intermediate, such as 4a, 4b or 4e, in large quantities, particularly in light of the good stability of the cyanoethyl and tosyl protecting groups. As a simple example of this protocol, it has previously been shown that caesium hydroxide monohydrate (CsOH·H2O) and methyl

Are D-manno-configured Amadori products ligands of the bacterial lectin FimH?

• Tobias-Elias Gloe,
• Insa Stamer,
• Cornelia Hojnik,
• Tanja M. Wrodnigg and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 1096–1104, doi:10.3762/bjoc.11.123

• cleavage of the protecting groups, employing Zemplén conditions to remove acetyl groups [18][19] followed by acidic cleavage of the isopropylidene groups, the desired starting material for the Amadori rearrangement, a mixture of D-glycero-D-galacto/D-talo heptopyranoses (8a/b) was obtained in an overall

Synthesis of carbohydrate-scaffolded thymine glycoconjugates to organize multivalency

• Anna K. Ciuk and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 668–674, doi:10.3762/bjoc.11.75

• optimized procedure employing DBU and TBAI at rt [5] over two days to deliver the protected glycothymine derivative 12 in 64% yield. The acetyl protecting groups were cleaved employing Zemplén’s procedure [30]. During work-up with acidic ionic exchange resin, surprisingly cleavage of the isopropylidene