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

Synthesis of multivalent carbohydrate mimetics with aminopolyol end groups and their evaluation as L-selectin inhibitors

• Joana Salta,
• Jens Dernedde and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2015, 11, 638–646, doi:10.3762/bjoc.11.72

• first model reaction protected aminopyran 3 was treated with commercially available hexanoyl chloride affording the desired amide 4 in excellent yield. After cleavage of the TBS protecting groups, the fully deprotected monovalent aminopyran derivative 5 was isolated in quantitative yield. After the

• since in the literature similar conditions were found for the synthesis of multivalent acetyl-protected carbohydrates [29]. As possible explanation we assume that the formation of product 6 is sterically too hindered due to the bulkiness of the TBS-protecting groups of 3 and the short distance between

Automated solid-phase synthesis of oligosaccharides containing sialic acids

• Chian-Hui Lai,
• Heung Sik Hahm,
• Chien-Fu Liang and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2015, 11, 617–621, doi:10.3762/bjoc.11.69

• group with triethylamine uncovered the hydroxy group to serve as the nucleophile in the next coupling. Participating protecting groups at the C2 position of building blocks 6, 7, 9 and 10 ensured selective formation of β-glycosidic linkages during the glycosylations. These building blocks resulted in

• carbonate protecting groups [23][25]. The addition of dioxane to CH2Cl2 resulted in preferred formation of the α-anomer, an effect that is well known from solution phase syntheses [26] (Table S6, Figure S1 in Supporting Information File 1). When five equivalents of building block 8 were used at 20 °C for 90

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• derivatives of many amino acids often become annoyingly strenuous due to the necessity of employing protecting groups, on one or more of the amino acid functionalities, during the synthetic sequence. However, in the case of hydroxyamino acids such as hydroxyproline, serine, threonine, tyrosine and 3,4

A simple and efficient method for the preparation of 5-hydroxy-3-acyltetramic acids

• Johanna Trenner and
• Evgeny V. Prusov

Beilstein J. Org. Chem. 2015, 11, 323–327, doi:10.3762/bjoc.11.37

• amounts of Pd trifluoroacetate/dppp [18] gave no conversion. In summary, we have developed a simple and efficient method for the synthesis of 5-hydroxy-3-acyltetramic acids by oxidation of the corresponding bisenolates with molecular oxygen. We have also investigated the cleavage of various protecting

• groups from the nitrogen of tetramic acids. Application of this methodology to a broader scope of substrates as well as to the total synthesis of natural products is currently underway in our laboratory and will be reported in due course. Experimental General procedure for the oxidation of tetramic acids

Articulated rods – a novel class of molecular rods based on oligospiroketals (OSK)

• Pablo Wessig,
• Roswitha Merkel and
• Peter Müller

Beilstein J. Org. Chem. 2015, 11, 74–84, doi:10.3762/bjoc.11.11

• ) with orthogonal protecting groups at both ends, ii) selective deprotection/activation of each of these groups, iii) construction of the joint, iv) functionalizing the terminal positions of the ARs, and v) (possibly) introduction of solubility enhancing groups. Our strategy is summarized in Figure 3. We

Synthesis of antibacterial 1,3-diyne-linked peptoids from an Ugi-4CR/Glaser coupling approach

• Martin C. N. Brauer,
• Ricardo A. W. Neves Filho,
• Bernhard Westermann,
• Ramona Heinke and
• Ludger A. Wessjohann

Beilstein J. Org. Chem. 2015, 11, 25–30, doi:10.3762/bjoc.11.4

• to note that different protecting groups can be used: Boc-, PhAc- and Cbz-protected peptoid derivatives (Table 1, entries 8–10) reacted to the corresponding dimers 7h–j without complications. The structure of the compounds 7a–j, as well as 8a–j, have been confirmed by 1H, 13C NMR spectra, and HRMS

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• the product formed. It was argued the protecting group would influence and stabilise the N-acyliminium ion formed, therefore altering the regioselectivity of the product obtained. It was found that in all cases (e.g., carbonyl or sulfonyl-based protecting groups and ring size, n = 1 or 2) the kinetic

Versatile synthesis of amino acid functionalized nucleosides via a domino carboxamidation reaction

• Vicky Gheerardijn,
• Jos Van den Begin and
• Annemieke Madder

Beilstein J. Org. Chem. 2014, 10, 2566–2572, doi:10.3762/bjoc.10.268

• functionalities on the corresponding nucleoside building blocks to avoid side-reactions during DNA synthesis. Not only should these protecting groups be stable under all chemical conditions used in the synthesis pathway, they should also be stable under the DNA synthesis conditions and easily removable after

• considerations, coupling of the TBDMS-protected nucleoside 1 with histidine methyl ester 2 followed by in situ t-Boc protection of the free hydrogen on the imidazole functionality gave the desired compound 3 in satisfying yield. In the next step of the synthesis, the TBDMS-protecting groups needed to be removed

• Scheme 3. Protected lysine 10 is commercially available and was coupled with the TBDMS-protected nucleoside 1 to afford product 11 in high yield. After deprotection of the tert-butyldimethylsilyl protecting groups using the above described protocol, modified nucleoside 12 could be selectively protected

Synthesis of aromatic glycoconjugates. Building blocks for the construction of combinatorial glycopeptide libraries

• Markus Nörrlinger and
• Thomas Ziegler

Beilstein J. Org. Chem. 2014, 10, 2453–2460, doi:10.3762/bjoc.10.256

• gave non-glycosylated fully protected dipeptides 17 and 20 in 73% and 88% yield, respectively (Scheme 2). Likewise, the Fmoc protecting groups in glucosylated building blocks 13a and 14a were first removed with piperidine in DMF to give crude aminomethyl derivates 21 and 23. Next, the latter were