Development of a fluorogenic small substrate for dipeptidyl peptidase-4

• Futa Ogawa,
• Masanori Takeda,
• Kanae Miyanaga,
• Keita Tani,
• Ryuji Yamazawa,
• Kiyoshi Ito,
• Atsushi Tarui,
• Kazuyuki Sato and
• Masaaki Omote

Beilstein J. Org. Chem. 2017, 13, 2690–2697, doi:10.3762/bjoc.13.267

• information All experiments were carried out under an argon atmosphere in flame-dried glassware using standard inert techniques for introducing reagents and solvents, unless otherwise noted. N,N-Dimethylformamide (DMF) was distilled over calcium hydride and stored in a bottle with activated molecular sieves

A Brønsted base-promoted diastereoselective dimerization of azlactones

• Danielle L. J. Pinheiro,
• Gabriel M. F. Batista,
• Pedro P. de Castro,
• Leonã S. Flores,
• Gustavo F. S. Andrade and
• Giovanni W. Amarante

Beilstein J. Org. Chem. 2017, 13, 2663–2670, doi:10.3762/bjoc.13.264

• significant anti-angiogenesis activity [31]. It is worth mentioning that this product has three consecutive stereocenters and different sites of variation from the original natural product. The hydride comes from the less hindered side of the ketone moiety, leading to the formation of a hydroxy group in cis

Recent progress in the racemic and enantioselective synthesis of monofluoroalkene-based dipeptide isosteres

• Myriam Drouin and
• Jean-François Paquin

Beilstein J. Org. Chem. 2017, 13, 2637–2658, doi:10.3762/bjoc.13.262

• HWE olefination (Scheme 5). The (E)-monofluoroalkene was thus obtained in an excellent selectivity using n-butyllithium in tert-butyl methyl ether. The resulting ester 21 was reduced using lithium aluminum hydride, and treatment with tartaric acid deprotected the OBO, thus providing the free triol 22

An efficient synthesis of 1,6-anhydro-N-acetylmuramic acid from N-acetylglucosamine

• Matthew B. Calvert,
• Christoph Mayer and
• Alexander Titz

Beilstein J. Org. Chem. 2017, 13, 2631–2636, doi:10.3762/bjoc.13.261

• -Triphenylmethyl-1,6-anhydro-N-acetylmuramic acid (13) A solution of 12 (910 mg, 2.0 mmol) in dioxane (16 mL) was treated with sodium hydride (60% suspension in mineral oil, 540 mg, 13.5 mmol) at room temperature. The suspension was warmed to 45 °C for 10 minutes, then cooled to rt. (S)-2-Chloropropionic acid

• ) was treated with sodium hydride (60% suspension in mineral oil, 130 mg, 3.3 mmol) at room temperature. The suspension was warmed to 45 °C for 10 minutes, then cooled to rt. (±)-2-Chloropropionic acid (130 mg, 110 µL, 1.2 mmol) was added, and the suspension stirred at 90 °C for 3 hours. The reaction

Palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides

• Tao Fan,
• Wei-Dong Meng and
• Xingang Zhang

Beilstein J. Org. Chem. 2017, 13, 2610–2616, doi:10.3762/bjoc.13.258

• of secondary fluoroalkylated alkyl bromides with alkenes remains a challenge and has not been reported so far [28][29][30][31][32] due to the sluggish oxidative addition [33] of alkyl halides to palladium and facile β-hydride elimination [34][35] of alkylpalladium species. Additionally, the resulting

• begins with the reaction of [PdLn(0)] with secondary trifluoromethylated 2 via a SET pathway to generate alkyl radical B. B subsequently reacts with alkene to produce new radical species D, which then recombines with [LnPd(I)Br] C to give the key palladium-complex E. Finally, a β-hydride elimination

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone

• Kai Zhang,
• Shenglan Liu,
• Anjun Liu,
• Hongxin Chai,
• Jiarong Li and
• Lamusi A

Beilstein J. Org. Chem. 2017, 13, 2603–2609, doi:10.3762/bjoc.13.257

• ethylate the hydroxy group at 3-position of rhamnose. The structure of 2 was also ascertained by NMR. Then compound 2 was methylated at 0 °C in the presence of iodomethane and sodium hydride to afford 3. Finally, 3-O-ethyl-2,4-di-O-methylrhamnose (4) was obtained by the deprotection of 3 with Pd(PPh3)4 as

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• % yield. Surprisingly, an attempt to reduce the carbonyl function in adenine derivative 3 failed. The reaction performed at the same conditions as for 2 afforded a complex mixture of products. In order to solve this problem, lithium aluminum hydride was used as reducing agent. In this case, the reaction

• mesh ASTM). Triethylamine, dimethylformamide, and tetrahydrofuran were distilled and deoxygenated prior to use. Other solvents were of reagent grade and were used without prior purification. Thymine, adenine, 3-chloropropionyl chloride, lithium aluminum hydride, sodium borohydride, and aluminium

A permutation approach to the assignment of the configuration to diastereomeric tetrads by comparison of experimental and ab initio calculated differences in NMR data

• Przemysław J. Boratyński

Beilstein J. Org. Chem. 2017, 13, 2478–2485, doi:10.3762/bjoc.13.245

• , 132.1, 128.0, 122.25, 122.20, 119.9, 114.9, 100.4, 61.4, 57.4, 56.0, 55.8, 41.5, 39.5, 27.7, 27.2, 25.2 ppm; HRMS–ESI–TOF (m/z): [M + H]+ calcd for C22H26N5O, 376.2132; found, 376.2141. 9R-Phenyl-9-deoxyquinine (2b): Under inert gas (Ar), a sodium hydride dispersion (60% in mineral oil, 195 mg, 4.9 mmol

Herpetopanone, a diterpene from Herpetosiphon aurantiacus discovered by isotope labeling

• Xinli Pan,
• Nicole Domin,
• Sebastian Schieferdecker,
• Hirokazu Kage,
• Martin Roth and
• Markus Nett

Beilstein J. Org. Chem. 2017, 13, 2458–2465, doi:10.3762/bjoc.13.242

• configuration, thereby facilitating an intramolecular cyclization to a cyclodeca-1,5-diene by electrophilic attack of the allylic carbocation onto the corresponding double bond. A 1,3-hydride shift by Wagner–Meerwein rearrangement followed by another cyclization would then give rise to an octahydronaphthalene

• intermediate, two successive 1,3-hydride shifts and a final addition of OH− would yield obscuronatin (3). Interestingly, 3 was observed to undergo facile water elimination to give compound 4 [26]. Obscuronatin might thus serve as a biosynthetic intermediate or, alternatively, as a shunt product in the

Synthesis of ergostane-type brassinosteroids with modifications in ring A

• Vladimir N. Zhabinskii,
• Darya A. Osiyuk,
• Yuri V. Ermolovich,
• Natalia M. Chaschina,
• Tatsiana S. Dalidovich,
• Miroslav Strnad and
• Vladimir A. Khripach

Beilstein J. Org. Chem. 2017, 13, 2326–2331, doi:10.3762/bjoc.13.229

• ,3α-, and 2β,3β-dihydroxy-, 3-keto-, 3α- and 3β-hydroxy-, 2α-hydroxy-3-keto-) were synthesized from 2α,3α-diols in a few simple steps (Corey–Winter reaction, epoxidation, oxidation, hydride reduction, etc.). Keywords: biosynthetic precursors; brassinosteroids; diols; epibrassinolide; epicastasterone

• stereospecific C(3) → C(2)-hydride shift/elimination process [30]. So, tosylation of the diol 14 occurred regioselectively at the equatorial C-2 hydroxy group to give monotosylate 30, which upon heating in pyridine, yielded compound 31 (Scheme 6). Its treatment with KOH in methanol led to 24-epi-3

• -dehydroteasterone 32, which is unknown as a natural phytohormone. 3α- and 3β-alcohols of type 10 and 11 The hydride reduction of 3,6-diketones proceeds in a regioselective manner at the C-3 position [19]. Both 3α- and 3β-alcohols of type 10 and 11 (Scheme 1) can be obtained in this way depending on the reducing

An efficient synthesis of a C₁₂-higher sugar aminoalditol

• Łukasz Szyszka,
• Anna Osuch-Kwiatkowska,
• Mykhaylo A. Potopnyk and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2017, 13, 2146–2152, doi:10.3762/bjoc.13.213

• C75H79N3O11Na, 1220.5627; found, 1220.5612; Anal. calcd for C75H79N3O11: C, 75.16; H, 6.64; N, 3.51; found: C, 75.13; H, 6.82; N, 3.40. Method b: To a solution of 5 (0.3 g, 0.24 mmol) in dry THF (20 mL), LiAlH4 (55 mg, 1.45 mmol) was slowly added and the mixture was stirred for 1 h at 20 °C. Excess hydride was

• , 6.72; N, 0.88. To a stirred solution of 8 (0.35 g, 0.21 mmol) in DMF (20 mL) containing imidazole (1.5 mg), sodium hydride (60% dispersion in mineral oil, 80.6 mg, 2.1 mmol) was added, and the mixture was stirred at 20 °C for 30 min. Benzyl bromide (0.2 mL, 1.68 mmol) was added dropwise and the mixture

• was stirred for 24 h at 20 °C. Excess of hydride was decomposed by careful addition of water (5 mL) and the mixture was partitioned between water (30 mL) and ether (40 mL). The layers were separated and the aqueous one extracted with ethyl acetate (3 × 20 mL). The combined organic solutions were

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• ether 24 along with debrominated 25 as the major product (Table 2, entry 4). As before, irreversibly deprotonating the alcohol with sodium hydride was not productive (Table 2, entry 5). Using Pd2(dba)3 as catalyst precursor increased the yield of 24 relative to the amount of 25 produced, but the overall

Synthesis of benzannelated sultams by intramolecular Pd-catalyzed arylation of tertiary sulfonamides

• Valentin A. Rassadin,
• Mirko Scholz,
• Anastasiia A. Klochkova,
• Armin de Meijere and
• Victor V. Sokolov

Beilstein J. Org. Chem. 2017, 13, 1932–1939, doi:10.3762/bjoc.13.187

• contained a certain amount of water, so that the benzoates 10d,e underwent hydrolysis. Indeed, when the sultam 10e was treated with sodium hydride in freshly distilled dioxane followed by addition of a small amount of water, the acid 10h was isolated in an excellent yield of 93%. The relative stability of

• precursor 20 was prepared in one step from the respective sulfonamide 19 and 2-iodobenzyl alcohol employing a Mitsunobu protocol (Scheme 6) [49]. Treatment of 20 with palladium acetate, Ph3P, and sodium hydride in dioxane at 90 °С for 20 h furnished the target sultam 21 in 49% yield. Apparently, the

18-Hydroxydolabella-3,7-diene synthase – a diterpene synthase from Chitinophaga pinensis

• Jeroen S. Dickschat,
• Jan Rinkel,
• Patrick Rabe,
• Arman Beyraghdar Kashkooli and
• Harro J. Bouwmeester

Beilstein J. Org. Chem. 2017, 13, 1770–1780, doi:10.3762/bjoc.13.171

• cascade by attack of olefinic double bonds to the cationic centre, hydride shifts and Wagner–Meerwein rearrangements. The process is usually terminated by deprotonation or attack of water to yield a lipophilic terpene hydrocarbon or alcohol. Among the first investigated terpene synthases were the (+)- and

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• acceptor) or via oxidative dehydrogenation in the presence of appropriate oxidants. In absence of hydrogen acceptors, post dehydrogenation the hydrogen is released as H2↑. Catalysts such as iridium pincer complexes, CuAl2O3, hydroxyapatite bound palladium and ruthenium hydride complexes have been harnessed

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Phenylsilane as an effective desulfinylation reagent

• Wanda H. Midura,
• Aneta Rzewnicka and
• Jerzy A. Krysiak

Beilstein J. Org. Chem. 2017, 13, 1513–1517, doi:10.3762/bjoc.13.150

• reported. Apart from traditional hydride reducing agents like lithium aluminum hydride and sodium borohydride [1][2], different modifications were applied, using transition metal salts as catalysts or additives to change or enhance the properties of these reagents [3][4][5][6][7][8]. Hydrogenation is

• additionally chelated by both polar carbonyl substituents. It facilitates hydride anion formation, which attacks the most electrophilic center of a particular structure. Conclusion A phenylsilane/KOH system was successfully applied as a reducing agent for conversion of different cyclopropylcarboxylates to the

2-Methyl-2,4-pentanediol (MPD) boosts as detergent-substitute the performance of ß-barrel hybrid catalyst for phenylacetylene polymerization

• Julia Kinzel,
• Daniel F. Sauer,
• Marco Bocola,
• Marcus Arlt,
• Tayebeh Mirzaei Garakani,
• Andreas Thiel,
• Klaus Beckerle,
• Tino Polen,
• Jun Okuda and
• Ulrich Schwaneberg

Beilstein J. Org. Chem. 2017, 13, 1498–1506, doi:10.3762/bjoc.13.148

• -d1 was dried over calcium hydride, distilled, degassed and stored in a glove box. NMR spectra were recorded on a Bruker DRX 400 spectrometer (1H, 400.1 MHz). Chemical shifts were referenced internally by using the residual solvent resonances [50]. MALDI–TOF MS spectra were recorded on an Ultraflex

A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E

• Marcel Reimann,
• Louis P. Sandjo,
• Luis Antelo,
• Eckhard Thines,
• Isabella Siepe and
• Till Opatz

Beilstein J. Org. Chem. 2017, 13, 1430–1438, doi:10.3762/bjoc.13.140

• hydride, followed by Fmoc-protection and ozonolysis furnished aldehyde 5 in 57% yield over three steps (Scheme 2). The homoallylic alcohol was prepared by an enantioselective Duthaler–Hafner allylation [13] with the titanium-complex 15 in high yield and 94% ee. Attempts to perform a catalytic Keck

Sugar-based micro/mesoporous hypercross-linked polymers with in situ embedded silver nanoparticles for catalytic reduction

• Qing Yin,
• Qi Chen,
• Li-Can Lu and
• Bao-Hang Han

Beilstein J. Org. Chem. 2017, 13, 1212–1221, doi:10.3762/bjoc.13.120

• -linker, the Friedel–Crafts cross-linking polymerization is promoted smoothly by anhydrous FeCl3 in dry 1,2-dichloroethane (DCE). The monomers were either commercially available (Sug-1) or prepared (Sug-2 and Sug-3) by benzylation of free sugars with benzyl bromide and sodium hydride. The chemical

• precursors for the preparation of pharmaceuticals and agrochemicals. Experimental Synthesis of perbenzyl phenyl β-D-glucopyranoside (Sug-2) Sodium hydride (60%, 0.43 g, 10.85 mmol) was added portionwise to a solution of phenyl β-D-glucopyranoside (93 mg, 0.36 mmol) in DMF (5.0 mL) over 40 min under nitrogen

• –TOF) m/z: [M + Na] calcd for C40H40O6, 639.3; found: 639.4. Synthesis of perbenzyl methyl α-L-rhamnopyranoside (Sug-3) Sodium hydride (160 mg, 60%, 6.72 mmol) was added to a solution of methyl α-L-rhamnopyranoside (200 mg, 1.12 mmol) in DMF (5.0 mL) in an ice bath over 40 min under a nitrogen

Total syntheses of the archazolids: an emerging class of novel anticancer drugs

• Stephan Scheeff and
• Dirk Menche

Beilstein J. Org. Chem. 2017, 13, 1085–1098, doi:10.3762/bjoc.13.108

• efforts had to be invested, before acid 21 could be efficiently obtained as shown in Scheme 4. Finally, after optimization of a reported procedure [73] the successful route employed a one-pot process involving a sodium hydride-mediated coupling of methyl malonate 19 with iodoform (20) followed by a

A concise and practical stereoselective synthesis of ipragliflozin L-proline

• Shuai Ma,
• Zhenren Liu,
• Jing Pan,
• Shunli Zhang and
• Weicheng Zhou

Beilstein J. Org. Chem. 2017, 13, 1064–1070, doi:10.3762/bjoc.13.105

• other hypoglycemic agents. Only a few methods have been found in the literature about the synthesis of 1. It was reported that aryllithium reacted with per-hydroxy-protected D-glucono-1,5-lactone at −78 °C to obtain the lactol, followed by reduction with a large bulk silyl hydride in order to get high β

Transition-metal-free one-pot synthesis of alkynyl selenides from terminal alkynes under aerobic and sustainable conditions

• Adrián A. Heredia and
• Alicia B. Peñéñory

Beilstein J. Org. Chem. 2017, 13, 910–918, doi:10.3762/bjoc.13.92

• applications of alkynyl selenides are electrophilic addition reactions, many of them modulated by transition-metal catalysts [11]. Some examples are: hydroboration which results in a vinylborane selenide used in Pd-catalyzed Suzuki cross-coupling reactions [12], the addition to tributyltin hydride in the

Opportunities and challenges for the sustainable production of structurally complex diterpenoids in recombinant microbial systems

• Katarina Kemper,
• Max Hirte,
• Markus Reinbold,
• Monika Fuchs and
• Thomas Brück

Beilstein J. Org. Chem. 2017, 13, 845–854, doi:10.3762/bjoc.13.85

• labda-13-en-8-yl diphosphate carbocation intermediate and the formation of halima-5(10),13-dienyl diphosphate (Scheme 2). In wild-type Class II diterpene synthases, the labda-13-en-8-yl diphosphate carbocation undergoes either single deprotonation or a cascade of hydride and methyl group shifts prior to

• deprotonation with occasional hydration at the C8 position of the carbocation intermediate which yields hydroxylated diphosphate products [62]. MvCPS1, however, catalyzes a C9–C8 hydride shift preceding hydration resulting in the labdane-type diterpene precursor for the antidiabetic marrubiin [63]. Double

Nucleophilic and electrophilic cyclization of N-alkyne-substituted pyrrole derivatives: Synthesis of pyrrolopyrazinone, pyrrolotriazinone, and pyrrolooxazinone moieties

• Işıl Yenice,
• Sinan Basceken and
• Metin Balci

Beilstein J. Org. Chem. 2017, 13, 825–834, doi:10.3762/bjoc.13.83

• form the corresponding products by attack of lone pair electrons of the internal nitrogen or terminal nitrogen atoms, respectively. The 6-endo-dig cyclization follows only a proton shift to yield pyrrolopyrazinone skeleton 12, while 6-exo-dig follows first a proton shift and then an [1,3]-hydride shift