Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• steps with a 25% overall yield. The reaction started with methyl 2,5-dimethoxy-3-nitrobenzoate, which was reduced into the corresponding aniline under hydrogen conditions with palladium on carbon. The aniline was further treated with Meldrum’s acid and trimethyl orthoformate to afford an enamine which

• has an orange-red color. Synthesis of arnoamines A (40) and B (41) The synthesis of arnoamines A and B was accomplished in nine and ten steps in 13% and 4% overall yield, respectively. The reaction started with 2-methoxy-5-nitroaniline treated with Meldrum’s acid (2,2-dimethyl-1,3-dioxane-4,6-dione

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• nitrate (40%, Scheme 56). Intramolecular Diels–Alder (DA) reaction: Suwa and co-workers [192] have synthesized the muscopyridine by a [4 + 2] cycloaddition of the bisketene 325. The condensation of acid dichloride derived from 323 with two molecules of Meldrum’s acid gave 324 which on thermal activation

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

• ] variant of Lacey–Dieckmann [8] condensation (Scheme 1) [9][10]. Reaction of either β-ketoester 4 or Meldrum’s acid derivative 9 with suitably protected glycine esters (5,6,10), followed by base-induced condensation furnished the desired tetramic acid model compounds as crystalline solids after treatment

Preparation of neuroprotective condensed 1,4-benzoxazepines by regio- and diastereoselective domino Knoevenagel–[1,5]-hydride shift cyclization reaction

• László Tóth,
• Yan Fu,
• Hai Yan Zhang,
• Attila Mándi,
• Katalin E. Kövér,
• Tünde-Zita Illyés,
• Attila Kiss-Szikszai,
• Balázs Balogh,
• Tibor Kurtán,
• Sándor Antus and
• Péter Mátyus

Beilstein J. Org. Chem. 2014, 10, 2594–2602, doi:10.3762/bjoc.10.272

• reaction with 1,3-dimethylbarbituric acid (12) and Meldrum’s acid (13), the reaction with malonitrile (14) stopped at the stage of the Knoevenagel product rac-7c with MgSO4 in CHCl3 and further cyclization did not occur when heated in DMSO at 150 °C or refluxed in n-butanol. The NMR data of 7a,b clearly

• (−9.32), 221 (−11.60). trans-2,2-Dimethyl-11'-nitro-2'-phenyl-1',2'-dihydro-7b'H,9'H-spiro[1,3-dioxane-5,8'-quinolino[1,2-d][1,4]benzoxazepine]-4,6-dione (rac-trans-7b): To the stirred solution of rac-5 (100 mg, 0.27 mmol) in chloroform (5 mL), anhydrous MgSO4 (150 mg, 1.25 mmol) and Meldrum’s acid (54

• aromatic substitution by using 2-fluoro-5-nitrobenzaldehyde (11b) to give rac-5 containing a tertiary arylamine nitrogen in 71% yield. With the 2-chloro-5-nitrobenzaldehyde reagent, only 3% yield for rac-5 could be achieved. Subsequently rac-5 was reacted with 1,3-dimethylbarbituric acid (12), Meldrum’s

Multicomponent reactions in nucleoside chemistry

• Mariola Koszytkowska-Stawińska and
• Włodzimierz Buchowicz

Beilstein J. Org. Chem. 2014, 10, 1706–1732, doi:10.3762/bjoc.10.179

• Knoevenagel condensation, the Michael addition, and the N-nucleophilic cyclization (Scheme 24) [94]. Whereas 5,5-dimethylcyclohexane-1,3-dione (66) or Meldrum’s acid (67) acted as the Knoevenagel donor, 3-methyl-1-phenyl-1H-pyrazol-5-amine (68) played the role of the Michael donor in these reactions. The

Synthesis and antibacterial activity of monocyclic 3-carboxamide tetramic acids

• Yong-Chul Jeong and
• Mark G. Moloney

Beilstein J. Org. Chem. 2013, 9, 1899–1906, doi:10.3762/bjoc.9.224

• generality [20][21]. We found that an approach based upon direct acylation of methyl thioethers 8a,b (these were readily obtained from the required N-acylmethionine by DCC/DMAP coupling with Meldrum’s acid and cyclisation under reflux) was possible, which made use of the high acidity of the tetramate system

Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis

• Aleksey I. Gerasyuto,
• Zhi-Xiong Ma,
• Grant S. Buchanan and
• Richard P. Hsung

Beilstein J. Org. Chem. 2013, 9, 1170–1178, doi:10.3762/bjoc.9.131

• by condensation with Meldrum’s acid in the presence of Ni(acac)2. Treatment of 23 with MeONa in MeOH under reflux gave vinylogous urethane 24. It is noteworthy that the geometry of the vinylogous urethane double bond exclusively favored Z, presumably due to the internal hydrogen bonding. Cleavage of

Reductions of aldehydes and ketones with a readily available N-heterocyclic carbene borane and acetic acid

• Vladimir Lamm,
• Xiangcheng Pan,
• Tsuyoshi Taniguchi and
• Dennis P. Curran

Beilstein J. Org. Chem. 2013, 9, 675–680, doi:10.3762/bjoc.9.76

• ethyl acetate (EtOAc) was complete in 30 min and gave 3-phenylpropanol (3) in 86% yield after evaporation and flash chromatography (Scheme 2). Other acids including pyridinium p-toluenesulfonate, benzohydroxamic acid, and 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum’s acid) also promoted this reduction

The preparation of 3-substituted-1,5-dibromopentanes as precursors to heteracyclohexanes

• Bryan Ringstrand,
• Martin Oltmanns,
• Jeffrey A. Batt,
• Aleksandra Jankowiak,
• Richard P. Denicola and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2011, 7, 386–393, doi:10.3762/bjoc.7.49

• the range of 25–85%, whereas the decarboxylation step gives the corresponding glutaric acids in 60–80% yield [19][33]. Variations of Method 1B involve the use of cyanoacetamide [34][35][36] or Meldrum’s acid [19][37] instead of malonate diester. For the former, the condensation with aldehyde is

Synthesis of some novel annulated pyrido[2,3-d]pyrimidines via stereoselective intramolecular hetero Diels–Alder reactions of 1-oxa-1,3-butadienes

• Mohit L. Deb and
• Pulak J. Bhuyan

Beilstein J. Org. Chem. 2010, 6, No. 11, doi:10.3762/bjoc.6.11

• containing water (8 ml). Two drops of piperidine (in case of Meldrum’s acid (4b), piperidine acetate was used) were added and the mixture stirred for 4 h. The solid was removed by filtration and recrystallized from ethanol to afford a white solid (769 mg, 88%). The compound was assigned structure 5a from a