(−)-Complanine, an inflammatory substance of marine fireworm: a synthetic study

• Kazuhiko Nakamura,
• Yu Tachikawa and
• Daisuke Uemura

Beilstein J. Org. Chem. 2009, 5, No. 12, doi:10.3762/bjoc.5.12

• Discussion Our synthesis started from the known compound 3 [5][6] that could be derived from (R)-malic acid, (R)-2, in three steps (1. BH3·SMe2; 2. cat. TsOH, Et2CO; 3. TsCl, pyridine) (Scheme 1). The resultant tosylate 3 was treated with lithium acetylide ethylenediamine complex to give the terminal

• Synthesis of alkyne 4: To a solution of tosylate (3, 3.00 g, 9.1 mmol) in DMSO (10 ml), a lithium acetylide ethylene diamine complex (1.00 g, 11.0 mmol) was added under nitrogen atmosphere. After stirring for 3 h, an extractive workup and column chromatography (SiO2, hexane/ethyl acetate 99 : 1) gave the

Recent progress on the total synthesis of acetogenins from Annonaceae

• Nianguang Li,
• Zhihao Shi,
• Yuping Tang,
• Jianwei Chen and
• Xiang Li

Beilstein J. Org. Chem. 2008, 4, No. 48, doi:10.3762/bjoc.4.48

• 199 to 200 in the presence of InCl3 afforded the bis-adduct, anti-diol 201. The derived tosylate 202 was converted to the bis-THF core unit 203 upon treatment with TBAF. Oxidation to aldehyde 204 followed by InCl3-promoted addition of the (S)-allylic stannane 205 gave the anti adduct 206. Removal of

• the OH group by reduction of the tosylate 207 with LiBEt3H yielded the SEM ether 208. Conversion to the vinyl iodide 209 followed by Pd0-catalyzed coupling with the (S)-alkynyl butenolide 210 gave the asiminocin precursor 211. Selective hydrogenation of the enyne moiety with diimide and cleavage of

Convenient method for preparing benzyl ethers and esters using 2-benzyloxypyridine

• Susana S. Lopez and
• Gregory B. Dudley

Beilstein J. Org. Chem. 2008, 4, No. 44, doi:10.3762/bjoc.4.44

• the synthesis of benzyl ethers are equally relevant for the synthesis of halobenzyl ethers (3a → 7, 98% yield). Finally, replacement of methyl triflate with less reactive methylating reagents, including dimethyl sulfate (Me2SO4), methyl tosylate (MeOTs), and methyl iodide (MeI), did not provide

• [33][34] (2-chloro-1-methylpyridinium iodide). If release of the reactive benzyl electrophile (which begins to occur upon warming) competes with N-methylation of pyridine, then side reactions and alternative pathways emerge. For example, Paquette and co-workers report that the use of methyl tosylate

Dimerization of propargyl and homopropargyl 6-azido- 6-deoxy- glycosides upon 1,3-dipolar cycloaddition

• Nikolas Pietrzik,
• Daniel Schmollinger and
• Thomas Ziegler

Beilstein J. Org. Chem. 2008, 4, No. 30, doi:10.3762/bjoc.4.30

• , the latter was stirred with NaN3 in DMF (48 h, 65 °C) to afford 4a in 44% yield. The preparation of compound 4a via the corresponding tosylate 3a was somewhat more convenient than the synthesis via the 6-bromo-6-deoxy counterpart 3a'' and resulted in a similar overall yield. Therefore, all other 6

A divergent asymmetric approach to aza-spiropyran derivative and (1S,8aR)-1-hydroxyindolizidine

• Jian-Feng Zheng,
• Wen Chen,
• Su-Yu Huang,
• Jian-Liang Ye and
• Pei-Qiang Huang

Beilstein J. Org. Chem. 2007, 3, No. 41, doi:10.1186/1860-5397-3-41

• leading to the bicyclic indolizidine.[40] Second, we have also observed that the tosylate of 8 is too labile to be isolated, and mesylate 12 decomposed upon flash column chromatography on silica gel, which are due to the spontaneous formation of a polar quaternary ammonium salt. In addition, the presence

Vinylogous Mukaiyama aldol reactions with 4-oxy-2-trimethylsilyloxypyrroles: relevance to castanospermine synthesis

• Roger Hunter,
• Sophie C. M. Rees-Jones and
• Hong Su

Beilstein J. Org. Chem. 2007, 3, No. 38, doi:10.1186/1860-5397-3-38

• -game sequence. Interestingly, the N-Boc group appears in its s-trans form, with the carbonyl oxygen pointing away from C-4. Compound 16 was then converted in high yield to tosylate 17 for the final cyclization, hydrolysis and reduction sequence to target (Scheme 5). Exposure of 17 to TFA at 0°C

• followed by addition of Hünig's base resulted in cyclization to indolizidine 18, which was isolated chromatographically as a tosylate salt in 56% yield. Compound 18 was identified from its NMR data. In particular, C-3(H-3), C-5(H-5) and C-8a(H-8a) resonated ≈ 10 ppm (C) and 1 ppm (H) downfield respectively

Synthesis of phosphorothioates using thiophosphate salts

• Babak Kaboudin and
• Fatemeh Farjadian

Beilstein J. Org. Chem. 2006, 2, No. 4, doi:10.1186/1860-5397-2-4

• route to phosphorothioates via O,O'-dialkyl thiophosphate anion formation. Studies on the reaction of ambident nucleophile ammonium O,O'-diethyl thiophosphate with benzyl halides and tosylate in different solvents show that only S-alkylation is obtained. Reaction of this ambident nucleophile with

• this reagent with benzyl bromide, chloride and tosylate in different aporotic and protic solvents show that S-benzyl O,O'-diethyl phosphorothioate (S-alkylation) was formed as sole product (Scheme 4). We conclude here that changing of leaving group and use of different media gives no O-alkylation

• on the reaction of ambident nucleophile ammonium O,O'-diethyl thiophosphate with benzyl halides and tosylate in different solvents show that only S-alkylation will be obtained as sole product. Reaction of this ambident nucleophile with benzoyl chloride (hard electrophilic center), gave the O