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

• to use 6-azido-3-deazapurine ribonucleoside as key intermediate Our initial attempts to create an efficient route to c3A started with the smooth transformation of commercially available 4-chloroimidazo[4,5-c]pyridine with lithium azide to provide 4-azidoimidazo[4,5-c]pyridine (1) [27] (Scheme 3

Efficient mechanochemical synthesis of regioselective persubstituted cyclodextrins

• Laszlo Jicsinszky,
• Marina Caporaso,
• Katia Martina,
• Emanuela Calcio Gaudino and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2016, 12, 2364–2371, doi:10.3762/bjoc.12.230

• friendly procedures. Ball mill assisted syntheses are good alternatives to overcome solubility difficulties in syntheses or isolation of natural compounds from vegetables using CDs [9][10]. Environmentally benign synthetic methods of CD derivatives have been recently reviewed [11]. The key intermediate in

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

• afforded the free amino acid in four steps via key intermediate 4-hydroxyarginine 62. The synthesis of nitro alcohol 61 was not described but its preparation has been reported [65]. All four diastereomers were synthesised for comparison with the isolated enduracididine sample. Synthesis of L-allo

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

• Paul B. Geraghty,
• Calvin Lee,
• Jegadesan Subbiah,
• Wallace W. H. Wong,
• James L. Banal,
• Mohammed A. Jameel,
• Trevor A. Smith and
• David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

• donors via chain extension catenation of alkylthiophenes. We have used commercially available 3-butyl-, 3-hexyl- and 3-octylthiophene to form the key intermediate TMS-alkylthiophene boronic acid pinacol esters (3) in high yield on a large scale and in high purity as they can be purified by distillation

A new and expeditious synthesis of all enantiomerically pure stereoisomers of rosaprostol, an antiulcer drug

• Wiesława Perlikowska,
• Remigiusz Żurawiński and
• Marian Mikołajczyk

Beilstein J. Org. Chem. 2016, 12, 2234–2239, doi:10.3762/bjoc.12.215

• methanephosphonate into (±)-1 was achieved in only seven steps and in 42% overall yield. Racemic 2-dimethoxyphosphoryl-3-hexylcyclopentan-1-one (3) is the key intermediate in this synthesis. This report describes the resolution of (±)-3 into its enantiomers and their application as starting chiral reagents for the

The direct oxidative diene cyclization and related reactions in natural product synthesis

• Juliane Adrian,
• Leona J. Gross and
• Christian B. W. Stark

Beilstein J. Org. Chem. 2016, 12, 2104–2123, doi:10.3762/bjoc.12.200

• in Scheme 3). The key intermediate and cyclization precursor may then involve a coordinative bond of that ether oxygen to the strongly Lewis acidic metal center. Due to the close relation to type B cyclizations, they can be classified as type B’ (Scheme 3). Reagents that mediate this type of reaction

• was intramolecularly trapped by attack of the remote hydroxy group to afford bis-THF 54, a key intermediate en route to membranacin (55) (Scheme 12) [102]. One year later, in 2005, Brown and co-workers achieved a total synthesis of 21,22-diepi-membrarollin (60) [105], possessing an adjacent bis-THF

• an oxidative cyclization using stoichiometric amounts of sodium permanganate to furnish trans-THF diol 78 in 73% yield with an excellent diastereomeric ratio of 97:3 induced by a cyclohexanol derived chiral auxiliary. This key intermediate was subsequently converted to natural trans-(+)-linalool

Beta-hydroxyphosphonate ribonucleoside analogues derived from 4-substituted-1,2,3-triazoles as IMP/GMP mimics: synthesis and biological evaluation

• Tai Nguyen Van,
• Audrey Hospital,
• Corinne Lionne,
• Lars P. Jordheim,
• Charles Dumontet,
• Christian Périgaud,
• Laurent Chaloin and
• Suzanne Peyrottes

Beilstein J. Org. Chem. 2016, 12, 1476–1486, doi:10.3762/bjoc.12.144

• synthesis of 1,2,3-triazolonucleotides (1a–o, Figure 1) was envisaged using the Huisgen 1,3-dipolar cycloaddition of the azido-sugar-phosphonate key-intermediate 2 (Scheme 1) and selected commercially available alkynes. Thus, (1-azido-2,5-di-O-acetyl-3-O-benzoyl-6-deoxy-6-diethylphosphono)-β-ribo-(5S

Synthesis of ferrocenyl-substituted 1,3-dithiolanes via [3 + 2]-cycloadditions of ferrocenyl hetaryl thioketones with thiocarbonyl S-methanides

• Grzegorz Mlostoń,
• Róża Hamera-Fałdyga,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 1421–1427, doi:10.3762/bjoc.12.136

• 1,5-diradical as a key intermediate. The complete change of the reaction mechanism toward the concerted [3 + 2]-cycloaddition was observed in the reaction of a sterically crowded cycloaliphatic thiocarbonyl ylide with ferrocenyl methyl thioketone. Keywords: [3 + 2]-cycloadditions; 1,3-dithiolanes

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

• ’-position of the BINOL backbone had a remarkable effect on the catalytic activity and enantioselectivity. Based on this method, the authors also achieved the synthesis of a key intermediate efficiently (99% yield and 93% ee), which had been used in the total synthesis of (+)-folicanthine [68]. The Zhang

A robust synthesis of 7,8-didemethyl-8-hydroxy-5-deazariboflavin

• Matthias Bender,
• Henrik Mouritsen and
• Jens Christoffers

Beilstein J. Org. Chem. 2016, 12, 912–917, doi:10.3762/bjoc.12.89

• transformed to the corresponding protected ribitylamine via the oxime, which was submitted to reduction with LiAlH4. Key advantage compared to previous syntheses is the utilization of a polyol-protective group which allowed the chromatographic purification of a key-intermediate product providing the target

• biosynthetic precursor compound to cofactor F420. In comparison with older routes to this target compound, the key innovation of our procedures is the introduction of two isopropylidene protective groups into the ribose side chain, which allowed the chromatographic purification of key intermediate product 11

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

• . synthesised the hydroxyleucine moiety found in naturally occurring muraymycins of classes A to C (Scheme 8) [107]. Adapting a strategy developed by Zhu et al., D-serine (59) was stereoselectively converted into the protected amino alcohol 60 [108]. Key intermediate 60 was then Cbz- and acetonide protected to

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• Strecker degradation was proposed, which includes the anion formed by deprotonation of the carboxyl group as the key intermediate [28][29]. Indeed during geometry optimization we found that the decarboxylation of the anion formed from glycine and ninhydrin occurs without significant energy barrier. This

• decarboxylation. Since the parent zwitterions 5 and 6 cannot be calculated as energy minima, there is no chance to understand, e.g., which conformations of 5 will lead preferentially to 7a and 7b, respectively. Since it was found experimentally that the amine 12 is the key intermediate for the formation of

• hydrolysis of 11 was detected. This observation suggests that 10 is formed preferentially, and thus the key intermediate is rather 7b and not 8. Such proposal is supported by the calculated activation barrier for the formation of 10 from 7b which is slightly lower (2.2 kcal/mol) than the corresponding

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• constructed via a desymmetrization aza-Michael reaction. That key intermediate 72 was afforded in 91% yield and 97% ee. (Scheme 25). In 2012, Cobb and co-workers developed a novel asymmetric Michael–Michael reaction between nitrohex-4-enoates 73 and nitroolefins 74 to construct a cyclohexene moiety, bearing

Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• . Monosubstituted CD derivative preparation Mono 6I-(p-toluenesulfonyl)-β-CD is the most popular of the CD derivatives because it is a key intermediate in the synthesis of important amino, azido, thio, thiocyanate and halo-derivatives. 6I-(p-toluenesulfonyl)-β-CD was efficiently prepared in an US-assisted procedure

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• disulfonylimidazole 42 to access a key intermediate easily converted to the corresponding di-2,3-mannoepoxido compound 43 (Scheme 8) [89]. The 3A,3B-diazido-3A,3B-dideoxy-bis(altro)-β-cyclodextrin 44 was then obtained by reaction of 43 with sodium azide and a copper(I)-catalyzed azide–alkyne cycloaddition finally

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

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

• Yusuke Kobayashi Ryuta Kuramoto Yoshiji Takemoto Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan 10.3762/bjoc.11.285 Abstract The first catalytic asymmetric synthesis of the key intermediate for beraprost has been achieved through an

• clinical application of 1, as well as the development of more active derivatives. Due to the unique tricyclic core of 1, which bears four contiguous stereocenters, various approaches for the synthesis of key intermediate 2 (Scheme 1) have been reported [14][15][16][17][18][19][20][21][22][23], including a

• few asymmetric syntheses relying on the optical resolution of racemic intermediates [16][17][18][23]. Herein we report the first catalytic asymmetric synthesis of the key intermediate 2 through organocatalyzed-enantioselective intramolecular oxa-Michael reaction [24][25][26]. Results and Discussion

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

• tertiary amide was then formed by sequential reaction of carboxylic acid 53 with oxalyl chloride and N-methylaniline derivative 54. The following two-step debenzylation sequence afforded alcohol 55 which was converted to the corresponding mesylate, serving as a key intermediate for the construction of the

• afforded coraxeniolide A (10) in 38% yield over three steps. Additionally, the enantioselective total synthesis of β-caryophyllene was realized starting from key intermediate 80. The route commenced with conjugate addition of silyl ketene acetal 81b to enone 80 from the sterically less hindered re-face

• proceed via the chair-like transition state 104, afforded key intermediate 105 with high diastereo- and enantioselectivity. Preparation of the δ-lactone 106 of the A ring of xeniolide F was then realized by treatment of Claisen product 105 with the methylene Wittig reagent, followed by desilylation and

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

• -ribofuranose (25) was then obtained in 33.13% overall yield after further treatment with acetic anhydride–acetic acid–sulfuric acid system. More than 200 g scale was achieved for the synthesis, and high purity (98%) product was obtained. This key intermediate 25 can be used to synthesize a variety of 3’-fluoro

• 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

• -3’-fluoro-6-methylpurine riboside 4, the analogue of biologically active natural product, 6-methylpurine-β-D-riboside (6-β-D-MPR). We constructed 3’-deoxy-3’-fluororibofuranosylpurine nucleosides 5–11 with various aromatic and heterocyclic moieties at position 6 from the key intermediate 26 by

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

• to explore the scope of the synthesis and isolation of spirooxazolines. Thus, the required key intermediate D-psicofuranose 2a was synthesized in four steps from the readily available starting material D-fructose following the literature procedure [42][47]. The C6–OH group of D-psicofuranose was

Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

• Wen Ding,
• Shaoyu Mai and
• Qiuling Song

Beilstein J. Org. Chem. 2015, 11, 2158–2165, doi:10.3762/bjoc.11.233

• scope. The mechanistic studies reveal that oxygen plays an essential role in the success of the amidation reactions with copper peroxycarboxylate as the key intermediate. Transamidation occurs smoothly between azole amide and a variety of amines. Keywords: amidation; azoles; Cu-catalyzed; molecular

• key intermediate to make the subsequent amide formation feasible (Scheme 1b). In our work, azoles have been chosen as the amines due to their special bioactivity [31]. To the best of our knowledge, Cu salt has not yet been used for catalyzed, oxidative direct amide formation. We report the first

• amidation reaction from carboxylic acids with peroxycarboxylate as the key intermediate, which represents a novel activation mode with molecular oxygen as the activating reagent. Most remarkably, in sharp contrast to previous reports (which used complex N-containing ligands to form copper superoxide

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• -halosuccinimide, X = Cl or Br). The application of different acids which participated in the in situ formation of acyl hypohalites enabled the selective generation of products 2 and 7 (Scheme 5). Notably, the C–H iodinated product of type 2 was also observed as key intermediate in the copper-catalyzed pyridinyl

Stereoselective synthesis of hernandulcin, peroxylippidulcine A, lippidulcines A, B and C and taste evaluation

• Marco G. Rigamonti and
• Francesco G. Gatti

Beilstein J. Org. Chem. 2015, 11, 2117–2124, doi:10.3762/bjoc.11.228

• the synthesis optimisation of the key intermediate 4 that can be prepared starting from (−)-isopulegol by two different approaches: i) oxidation of the hydroxy group to give (S)-isopulegone, which in turn is reduced stereospecifically into the desired cis diastereoisomer; or ii) by inversion of C(1

Synthesis, antimicrobial and cytotoxicity evaluation of new cholesterol congeners

• Mohamed Ramadan El Sayed Aly,
• Hosam Ali Saad and
• Shams Hashim Abdel-Hafez

Beilstein J. Org. Chem. 2015, 11, 1922–1932, doi:10.3762/bjoc.11.208

• each other. Conclusion In conclusion, cholesterol was successfully converted into 3β-azidocholest-5-ene (3) in good yield. This key intermediate, besides 3β-(prop-2-yn-1-yloxy)cholest-5-ene (10) were involved in a series of CuAAC reactions to afford a set of new modified cholesterols. The chalcone

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

• and co-workers [70] have described a total synthesis of norhalichondrin B in 37 steps from β-furylethanol. Interesting feature of this synthetic sequence is the tactical utilization of tandem ROM–RCM protocol towards the synthesis of the key intermediate 335. In this reaction, the required RRM

• precursor 333 was obtained from diazo ester 331 in five steps. Further, the RRM of 333 with catalyst 2 furnished the required pyran derivative 334 (71%). Next, the fused ether 334 was transformed into the desired intermediate 335 in eight steps, which is a key intermediate required for the synthesis of