- Blasticidin A as an inhibitor of aflatoxin production by Aspergillus parasiticus
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Blasticidin A, an antibiotic, showed strong inhibitory activity toward aflatoxin production by Aspergillus parasiticus. Its structure was characterized by NMR and chemical degradation experiments as 1, which is a tetramic acid derivative with a highly oxygenated long alkyl chain similar to aflastatin A (2). Absolute configurations of the eight chiral centers at C-4, 6, 31, 32, 33, 34, 35 and 37 of 1 were chemically determined. Blasticidin A almost completely inhibited aflatoxin production at 0.5 μm.
- Sakuda,Ono,Ikeda,Nakamura,Inagaki,Kawachi,Nakayama,Suzuki,Isogai,Nagasawa
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Read Online
- Development of an Efficient Process for the Decomposition of the Borate Complexes Formed during the Large-Scale Synthesis of (S)-1,2,4-Butanetriol
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An improved multikilogram-scale process for the production of (S)-1,2,4-butanetriol has been developed. This process involves the efficient removal of residual boric acid and the decomposition of the borate complexes formed during the reduction of (-)-dimethyl malate with sodium borohydride by methanolysis using a circular distillation-coupled hydrolysis apparatus.
- Liu, Qian,Xiong, Fang-Jun,He, Qiu-Qin,Chen, Fen-Er
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Read Online
- EXPERIMENTAL AND THEORETICAL STUDY OF THE STRUCTURES AND OPTICAL ROTATIONS OF CHIRAL BICYCLIC ORTHO ESTERS.
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The approach adopted in this study was to determine the structure of a single crystal of a pure enantiomer of one of the ortho esters by X-ray diffraction and then to utilize the coordinates so found for the bicyclic moiety in calculating the optical rotations of the remaining members of the series. Because of the high sensitivity of the calculated rotations to the atomic coordinates, this approach is subject to the experimental uncertainties inherent in the X-ray diffraction technique. Thus, we explore here some restrained refinement procedures to reduce the effect of these uncertainties on the calculated molar rotations. Study shows that the dipole interaction theory accomplishes this for the esters though it also reveals a potential hazard in establishing this connection for molecules wherein interactions of high order among atoms are significant.
- Wroblewski,Applequist,Takaya,Honzatko,Kim,Jacobson,Reitsma,Yeung,Verkade
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Read Online
- Optically active isonitrile ligand for palladium-catalyzed enantioselective bis-silylation of carbon-carbon double bonds
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Intramolecular bis-silylation of homoallylic alcohols proceeded enantioselectively in the presence of a catalyst prepared from Pd(acac), and optically active isonitriles, derived from a common chiral source, (+)-ketopinic acid.
- Suginome, Michinori,Nakamura, Hiroshi,Ito, Yoshihiko
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Read Online
- Biochemistry-Guided Prediction of the Absolute Configuration of Fungal Reduced Polyketides
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Highly reducing polyketide synthases (HR-PKSs) produce structurally diverse polyketides (PKs). The PK diversity is constructed by a variety of factors, including the β-keto processing, chain length, methylation pattern, and relative and absolute configurations of the substituents. We examined the stereochemical course of the PK processing for the synthesis of polyhydroxy PKs such as phialotides, phomenoic acid, and ACR-toxin. Heterologous expression of a HR-PKS gene, a trans-acting enoylreductase gene, and a truncated non-ribosomal peptide synthetase gene resulted in the formation of a linear PK with multiple stereogenic centers. The absolute configurations of the stereogenic centers were determined by chemical degradation followed by comparison of the degradation products with synthetic standards. A stereochemical rule was proposed to explain the absolute configurations of other reduced PKs and highlights an error in the absolute configurations of a reported structure. The present work demonstrates that focused functional analysis of functionally related HR-PKSs leads to a better understanding of the stereochemical course.
- Akimitsu, Kazuya,Guo, Yian,Hashimoto, Masaru,Kotani, Akari,Minami, Atsushi,Mochizuki, Susumu,Oikawa, Hideaki,Ozaki, Taro,Peng, Wenquan,Takino, Junya,Ye, Tao,Yu, Jie
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supporting information
p. 23403 - 23411
(2021/09/18)
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- IMMUNOMODULATORY GLYCOSPHINGOLIPIDS AND METHODS OF USE THEREOF
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Provided herein are a subset of alpha-galactosylceramide (alpha-GC) compounds having improved immunomodulatory activity, particularly with respect to NKT cell number and activity. Also provided herein are methods of use of such compounds, including in the modulation of NKT cells and/or activity in vivo. Further provided are combinatorial synthesis methods for generating alpha-GC compounds of specifically defined structure and thereby generating pure preparations thereof.
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Page/Page column 41; 43
(2020/08/28)
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- Preparation method of (S)-1, 2, 4-butantriol[7]
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The invention relates to a preparation method of (S)-1, 2, 4-butantriol, which comprises the following steps: reacting (S)-benzyloxymethyl ethylene oxide with a magnesium halide Grignard reagent of benzyl halomethyl ether to obtain (S)-1, 4-dibenzyloxy-2-butanol; and under the action of a palladium-carbon catalyst, hydrogenating to remove a benzyl protecting group to obtain a final product. The method is short in synthetic route, less in three wastes and suitable for industrial production.
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Paragraph 0034; 0040-0043; 0049-0050
(2020/05/05)
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- Synthesis of a C1-C12 Fragment of Gulmirecin B
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The synthesis of a C1-C14 fragment of the macrolide antibiotic gulmirecin B through formation of the C7-C8 bond by addition of a vinyllithium intermediate to a C1-C7 aldehyde was investigated. This crucial coupling was successful with a vinyllithium reagent corresponding to a C8-C12 fragment. The C8-C12 vinyl bromide was prepared from l -malic acid. The C1-C7 aldehyde building block was synthesized from hex-5-enoic acid by using an Evans alkylation, a cross-metathesis, and an asymmetric dihydroxylation as key steps.
- Maier, Martin E.,Rengarasu, Rathikrishnan
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supporting information
p. 1346 - 1350
(2019/06/20)
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- A S - (+) -3 - hydroxy tetrahydrofuran chemical synthesis method
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The invention discloses a S - (+) - 3 - hydroxy tetrahydrofuran chemical synthesis method, includes the following operation steps: 1, compound 1 in the presence of thionyl chloride and methanol reaction to obtain compound 2; 2, in the solvent, compound 2 in the presence of a reducing agent and the reaction to obtain compound 3; 3, compound 3 in the presence of paratoluene sulfonic acid, reaction to obtain compound S - (+) - 3 - hydroxy tetrahydrofuran.
- -
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Paragraph 0020-0022
(2019/04/04)
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- Stabilization of NaBH4 in Methanol Using a Catalytic Amount of NaOMe. Reduction of Esters and Lactones at Room Temperature without Solvent-Induced Loss of Hydride
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Rapid reaction of NaBH4 with MeOH precludes its use as a solvent for large-scale ester reductions. We have now learned that a catalytic amount of NaOMe (5 mol %) stabilizes NaBH4 solutions in methanol at 25 °C and permits the use of these solutions for the reduction of esters to alcohols. The generality of this reduction method was demonstrated using 22 esters including esters of naturally occurring chiral γ-butyrolactone containing dicarboxylic acids. This method permits the chemoselective reductions of esters in the presence of cyano and nitro groups and the reductive cyclization of a pyrrolidinedione ester to a fused five-membered furo[2,3-b]pyrrole and a (-)-crispine A analogue in high optical and chemical yields. Lactones, aliphatic esters, aromatic esters containing electron-withdrawing groups, and heteroaryl esters are reduced more rapidly than aryl esters containing electron-donating groups. The 11B NMR spectrum of the NaOMe-stabilized NaBH4 solutions showed a minor quartet due to monomethoxyborohydride (NaBH3OMe) that persisted up to 18 h at 25 °C. We postulate that NaBH3OMe is probably the active reducing agent. In support of this hypothesis, the activation barrier for hydride transfer from BH3(OMe)- onto benzoic acid methyl ester was calculated as 18.3 kcal/mol.
- Prasanth,Joseph, Ebbin,Abhijith,Nair,Ibnusaud, Ibrahim,Raskatov, Jevgenij,Singaram, Bakthan
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p. 1431 - 1440
(2018/02/09)
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- Nickel-Catalyzed Cross-Electrophile Coupling of Alkyl Fluorides: Stereospecific Synthesis of Vinylcyclopropanes
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The stereospecific reductive cross-electrophile coupling reaction of 2-vinyl-4-halotetrahydropyrans for vinylcyclopropane synthesis is reported. The nickel-catalyzed reaction occurs with both alkyl fluorides and alkyl chlorides. To the best of our knowledge, this is the first reported cross-electrophile coupling reaction of an alkyl fluoride. Ring contraction proceeds with high stereospecificity, providing selective synthesis of either diastereomer of di- and trisubstituted cyclopropanes. The utility of this methodology is demonstrated by several synthetic applications including the synthesis of the natural product dictyopterene A. 2-Vinyl-4-fluorotetrahydrofurans also undergo stereospecific ring contractions, providing access to synthetically useful hydroxymethyl cyclopropanes.
- Erickson, Lucas W.,Lucas, Erika L.,Tollefson, Emily J.,Jarvo, Elizabeth R.
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supporting information
p. 14006 - 14011
(2016/11/06)
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- VITAMIN D3 DERIVATIVES AND PHARMACEUTICAL USE THEREOF
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The present invention relates to vitamin D3 derivatives of the following formula, wherein each symbol has the same meaning as defined herein, and pharmaceutical or medical use thereof for treating metabolic disease, liver disease, obesity, diabetes, cardiovascular disease, or cancer in a patient in need thereof.
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Paragraph 0074
(2016/07/27)
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- Dibutyltin oxide mediated diastereoselective cyclodehydration/sulfonylation of 1,2,4-triols
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Dibutyltin oxide (Bu2SnO) mediated cyclodehydration or sulfonylation of 1,2,4-triols is predictably diastereoselective depending on the steric bulk of the substituents at C4. A larger difference (ΔA-value >1 kcal/mol) leads to the syn-1,2,4-triols favouring cyclodehydration (78-85%) to form 3-hydroxytetrahydrofurans, with the anti-1,2,4-triols favouring monosulfonylation (66-87%). Triols from symmetrical ketones preferentially undergo cyclodehydration in high yield (>75%) due to a gem-disubstituent effect. Thus, the 1,2,4-triols derived from simple cyclic ketones also favour cyclodehydration to form spirocyclic 3-hydroxytetrahydrofurans in 72-79% yields.
- Gamedze, Makhosazana P.,Nkambule, Comfort M.
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supporting information
p. 1825 - 1829
(2015/03/30)
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- Synthesis of racemic and enantiopure 3,4-methanonipecotic acid
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The synthesis of both racemic and enantiomerically pure (1R,6S)-3,4-methanonipecotic acid, a cyclopropane-containing β-amino acid, which is a valuable building block for drug discovery, is described. The synthetic scheme commences from natural (S)-malic acid and allows for the preparation of the title compound in 12 steps in 28% overall yield. A novel approach to the racemic 3,4-methanonipecotic acid, which relies on a Simmons-Smith cyclopropanation as the key step, was also developed. In this case, the product was obtained in 8 steps and 38% total yield.
- Tymtsunik, Andriy V.,Ivon, Yevhen M.,Komarov, Igor V.,Grygorenko, Oleksandr O.
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p. 1268 - 1272
(2015/11/09)
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- Preparation of (2R,4S)/(2S,4S)-4-hydroxypipecolinic acid derivatives from L-(-)-malic acid
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Synthetically important 4-hydroxypipecolinic acid derivatives were efficiently prepared from commercially available L-(-)-malic acid. The stereochemistries of the derivatives synthesized by our method were determined by coupling constant analyses with key methine protons on C2 and C4.
- Yin, Shuqiang,Taneda, Hiroshi,Li, Bozhi,Zhou, Dejun,Minato, Daishiro,Sugimoto, Kenji,Matsuya, Yuji
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p. 928 - 938
(2015/03/04)
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- Synthesis of non-hydrolysable mimics of glycosylphosphatidylinositol (GPI) anchors
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Synthesis of first generation non-hydrolysable C-phosphonate GPI analogs, viz., 6-O-(2-amino-2-deoxy-α-d-glucopyranosyl)-d-myo-inositol-1-O-(sn-3,4- bis(palmitoyloxy)butyl-1-phosphonate) 23a and 6-O-(2-amino-2-deoxy-α-d- glucopyranosyl)-d-myo-inositol-1-O-(sn-2,3-bis(palmitoyloxy)propyl-1- phosphonate) 23b, is reported. The target compounds were synthesized by the coupling of α-pseudodisaccharide 21 with phosphonic acids 18a and 18b respectively in quantitative yield followed by de-protection. These synthetic C-phosphonate GPI-probes were resistant to phosphatidylinositol specific phospholipase C (PI-PLC) and also showed moderate inhibition of the enzyme activity. The Royal Society of Chemistry.
- Yadav, Mahipal,Raghupathy, Riya,Saikam, Varma,Dara, Saidulu,Singh, Parvinder Pal,Sawant, Sanghapal D.,Mayor, Satyajit,Vishwakarma, Ram A.
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p. 1163 - 1172
(2014/02/14)
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- A stereoselective total synthesis of decarestrictine I
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A convergent and stereoselective total synthesis of decarestrictine I, a polyketide natural product, is described. Both acid and alcohol fragments were prepared from the readily available L-malic acid via Still-Gennari olefination and Sharpless asymmetric epoxidation. The Steglich esterification and ring-closing metathesis (RCM) are employed to combine both acid and alcohol fragments. Copyright
- Yadav, Jhillu Singh,Venkatesh, Miriyal,Kumar, Alleni Suman,Reddy, Poli Adi Narayana,Reddy, Basi V. Subba,Prasad, Attaluri R.
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p. 830 - 838
(2014/07/07)
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- Diastereoselective synthesis of the C14-C29 fragment of amphidinol 3
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An efficient stereoselective synthesis of the C14-C29 fragment highlighting a coupling reaction between a 1,3-dithiane derivative and an α-branched aldehyde was realized. This highly convergent synthesis involved two chiral pools, l-malic acid and (+)-camphorsulfonic acid, which are the starting compounds to control the six stereogenic centers present in the C14-C29 fragment of amphidinol 3.
- Rival, Nicolas,Hanquet, Gilles,Bensoussan, Charlelie,Reymond, Sebastien,Cossy, Janine,Colobert, Francoise
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p. 6829 - 6840
(2013/10/01)
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- Synthesis of a Cn-Cn+6 building block common to important polyol,polyene antibiotics from a divinylcarbinol by a desymmetrizing sharpless epoxidation
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A stereocontrolled synthesis of the enantiomerically pure epoxide 7b from propargyl ether 15 has been realized in 15 steps. Epoxide 7b represents a building block for the "eastern" moieties of the title compounds. Key steps in our approach were a desymmetrizing Sharpless epoxidation (→a€‰anti,cis-16), the selective processing of the bis-enolate of the bis(tert-butyl alkoxyacetate) 11 through a diastereoselective [2,3]-Wittig rearrangement (→a€‰syn,syn-9), and a stereo- and chemoselective iodolactonization (→a€‰35). The CO2H groups of dicarboxylic acid 37 were differentiated in a one-pot bis-oxidation reaction. The latter entailed the novel transformation of HO2CCH2-O-alkyl into AcOCH2-O-alkyl. The termini of a bis(tert-butyl alkoxyacetate) have been differentiated by forming the bis-enolate and engaging one enolate in a diastereoselective [2,3]-Wittig rearrangement. A diastereo- and chemoselective iodolactonization established the stereocenter of the epoxide ring. Copyright
- Nachbauer, Luc,Brueckner, Reinhard
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supporting information
p. 6545 - 6562
(2013/11/06)
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- Design, synthesis, biophysical and primer extension studies of novel acyclic butyl nucleic acid (BuNA)
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A novel nucleic acid analogue called acyclic (S)-butyl nucleic acid (BuNA) composed of an acyclic backbone containing a phosphodiester linkage and bearing natural nucleobases was synthesized. Next, (S)-BuNA nucleotides were incorporated in DNA strands and their effect on duplex stability and changes in structural conformation were investigated. Circular dichroism (CD), UV-melting and non-denatured gel electrophoresis (native PAGE) studies revealed that (S)-BuNA is capable of making duplexes with its complementary strands and integration of (S)-BuNA nucleotides into DNA duplex does not alter the B-type-helical structure of the duplex. Furthermore, (S)-BuNA oligonucleotides and (S)-BuNA substituted DNA strands were studied as primer extensions by DNA polymerases. This study revealed that the acyclic scaffold is tolerated by enzymes and is therefore to some extent biocompatible.
- Kumar, Vipin,Gore, Kiran R.,Pradeepkumar,Kesavan, Venkitasamy
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p. 5853 - 5865
(2013/09/12)
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- Improved synthesis of C8-C20 segment of pectenotoxin-2
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The C8-C20 segment of pectenotoxin-2 was efficiently synthesized in 16% overall yield in 22 steps from l-malic acid via an improved route.
- Fujiwara, Kenshu,Suzuki, Yuki,Koseki, Nao,Murata, Shun-Ichi,Murai, Akio,Kawai, Hidetoshi,Suzuki, Takanori
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scheme or table
p. 5589 - 5592
(2011/11/07)
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- Novel synthesis of stagonolide-F, putaminoxin and aspinolide-A
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Novel synthesis of putaminoxin, stagonolide-F and aspinolide-A have been achieved by utilizing (S) and (R)- malic acid. The key feature of the synthetic strategy includes Horner-Wittig olefination, double bond reduction and Steglich esterification. Olefinic acid for putaminoxin and stagonolide-F was prepared from (S)-malic acid whereas olefinic acid for aspinolide-A was prepared from (R)-malic acid and olefinic alcohols for putaminoxin, stagonolide-F and aspinolide-A were prepared by using Brown's asymmetric allylboration.
- Kamal, Ahmed,Reddy, Papagari Venkat,Balakrishna, Moku,Prabhakar, Singaraboina
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p. 143 - 149
(2013/01/10)
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- A new synthetic strategy for 2-deoxy-D-ribose via palladium(II)-catalyzed cyclization of aldehyde
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We achieved a total synthesis of 2-deoxy-D-ribose through intramolecular Pd(II)-catalyzed cyclization of aldehyde via an unstable hemiacetal intermediate as a key step. The Japan Institute of Heterocyclic Chemistry.
- Miyazawa, Masahiro,Awasaguchi, Ken-Ichiro,Uoya, Ikuyo,Yokoyama, Hajime,Hirai, Yoshiro
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experimental part
p. 1891 - 1902
(2011/04/12)
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- Stereocontrolled entry to the tricyclo[3.3.0]oxoheptane core of bielschowskysin by a [2+2] cycloaddition of an allene-butenolide
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As part of ongoing transannulation studies, the practical synthesis of an allene-linked γ-butenolide from l-malic acid and its substrate-controlled [2+2] photocycloaddition to the tricyclic core of bielschowskysin (1) are described.
- Miao, Ru,Gramani, Subramanian G.,Lear, Martin J.
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scheme or table
p. 1731 - 1733
(2009/07/05)
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- Spongipyran synthetic studies. Evolution of a scalable total synthesis of (+)-spongistatin 1
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Three syntheses of the architecturally complex, cytotoxic marine macrolide (+)-spongistatin 1 (1) are reported. Highlights of the first-generation synthesis include: use of a dithiane multicomponent linchpin coupling tactic for construction of the AB and CD spiroketals, and their union via a highly selective Evans boron-mediated aldol reaction en route to an ABCD aldehyde; introduction of the C(44)-C(51) side chain via a Lewis acid-mediated ring opening of a glucal epoxide with an allylstannane to assemble the EF subunit; and final fragment union via Wittig coupling of the ABCD and EF subunits to form the C(28)-C(29) olefin, followed by regioselective Yamaguchi macrolactonization and global deprotection. The second- and third-generation syntheses, designed with the goal of accessing 1 g of (+)-spongistatin 1 (1), maintain both the first-generation strategy for the ABCD aldehyde and final fragment union, while incorporating two more efficient approaches for construction of the EF Wittig salt. The latter combine the original chelation-controlled dithiane union of the E- and F-ring progenitors with application of a highly efficient cyanohydrin alkylation to append the F-ring side chain, in conjunction with two independent tactics to access the F-ring pyran. The first F-ring synthesis showcases a Petasis-Ferrier union/rearrangement protocol to access tetrahydropyrans, permitting the preparation of 750 mg of the EF Wittig salt, which in turn was converted to 80 mg of (+)-spongistatin 1, while the second F-ring strategy, incorporates an organocatalytic aldol reaction as the key construct, permitting completion of 1.009 g of totally synthetic (+)-spongistatin 1 (1). A brief analysis of the three syntheses alongside our earlier synthesis of (+)-spongistatin 2 is also presented.
- Smith III, Amos B.,Sfouggatakis, Chris,Risatti, Christina A.,Sperry, Jeffrey B.,Zhu, Wenyu,Doughty, Victoria A.,Tomioka, Takashi,Gotchev, Dimitar B.,Bennett, Clay S.,Sakamoto, Satoshi,Atasoylu, Onur,Shirakami, Shohei,Bauer, David,Takeuchi, Makoto,Koyanagi, Jyunichi,Sakamoto, Yasuharu
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scheme or table
p. 6489 - 6509
(2011/02/25)
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- Solid-phase synthesis of [5.5]-spiroketals
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An efficient and reliable multi-step synthesis of 251 natural product-like [5.5]-spiroketals on solid supports has been developed. As central key step, a double intramolecular hetero-Michael (DIHMA) reaction to alkynones was applied. The sequence allows for introduction of numerous substituents on the scaffold and for variation of stereochemistry. [5.5]-Spiroketals bearing an additional ketone were obtained in high overall yields. Further diversification was achieved by reduction of the ketone and reductive amination using polymer-supported borohydride, Grignard reaction and conversion to oxime derivatives in the solution phase.
- Sommer, Stefan,Kuehn, Marc,Waldmann, Herbert
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supporting information; experimental part
p. 1736 - 1750
(2009/08/14)
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- The first total synthesis of (-) and (+)-2-hydroxy-24-oxooctacosanolide using an effective lactonization
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(Chemical Equation Presented) An effective method for the total synthesis of 2-hydroxy-24-oxooctacosanolide, a defensive salivary secretion of the African termite Pseudacanthotermes spiniger, has been developed. The key lactonization to form a 29-membered ring lactone core is performed using 2-methyl-6- nitrobenzoic anhydride with a catalytic amount of 4-(dimethylamino)pyridine N-oxide.
- Shiina, Isamu,Kikuchi, Takaaki,Sasaki, Akane
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p. 4955 - 4958
(2007/10/03)
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- Process for preparing 1,2,4-butanetriol
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An object of the present invention is to provide a process wherein 1,2,4-butanetriol can be obtained safely, easily and inexpensively without causing problems concerning wastewater. A malic diester, 3-hydroxy-γ-butyrolactone or 3,4-dihydroxybutanoate represented by the following formulae (I), or a mixture thereof is reduced with sodium borohydride in an organic solvent to give 1,2,4-butanetriol represented by the following formula (II). When an optically active substance is used as the above-mentioned starting compound, substantially no recemization occurs during the reduction, and optically active 1,2,4-butanetriol is obtained.
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- PROCESS FOR PRODUCTION OF 1,2,4-BUTANETRIOL
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An object of the present invention is to provide a simple and low-cost process for preparing 1,2,4-butanetriol. Malic diester, 3-hydroxy-γ-butyrolactone or 3,4-dihydroxybutanoate represented by the following formula (I) or a mixture thereof, which is a raw material, is reduced in a medium in the presence of sodium borohydride to give 1,2,4-butanetriol represented by the following formula (II). In the process, sodium borohydride is added to a first alcohol, the raw material is added to a second alcohol which is different from the first alcohol, and they are reacted each other. In the formula, R is alkyl having four or less carbon atoms.
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Page/Page column 4-5
(2008/06/13)
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- METHOD FOR THE PRODUCTION OF OPTICALLY ACTIVE 2-AMINO-,2-CHLORO-,2-HYDROXY OR 2-ALKOXY-1-ALCOHOLS
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The invention relates to a method for the production of optically active 2-amino-, 2 chloro-, 2-hydroxy- or 2-alkoxy-1-alkanoles by catalytic hydrogenation of corresponding optically active 2-amino-, -chloro-, 2-hydroxy- and 2-alkoxy carboxylic acids or the acid derivatives thereof. According to the inventive method, hydrogenation is carried out in the presence of palladium and rhenium or catalysts containing palladium and rhenium.
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Page/Page column 9
(2008/06/13)
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- Stereoselective total synthesis of the nonenolide (+)-microcarpalide
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The enantiomer [(+)-1] of the nonenolide natural product microcarpalide [(-)-1] has been prepared from (S)-malic acid (3) and 3-decyn-1-ol (11) via a sixteen step sequence involving, inter alia, two metathesis processes.
- Banwell, Martin G.,Loong, David T. J.
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p. 713 - 734
(2007/10/03)
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- Stereoselection in radical cyclization of β-alkoxyvinyl sulfoxides: Synthesis of tetrahydrofuranyl allyl carbinols
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Equation presented. Tetrahydrofuranyl allyl carbinols may be prepared stereoselectively via radical cyclization of β-alkoxyvinyl sulfoxides, Pummerer rearrangement, and reaction with allylstannane.
- Keum, Gyochang,Kang, Soon Bang,Kim, Youseung,Lee, Eun
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p. 1895 - 1897
(2007/10/03)
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- Process for preparing 1,2, 4-butanetriol
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An object of the present invention is to provide a process wherein 1, 2,4-butanetriol can be obtained safely, easily and inexpensively without causing problems concerning wastewater. A malic diester, 3-hydroxy-γ-butyrolactone or 3,4-dihydroxybutanoate represented by the following formulae (I), or a mixture thereof is reduced with sodium borohydride in an organic solvent to give 1,2,4-butanetriol represented by the following formula (II). When an optically active substance is used as the above-mentioned starting compound, substantially no recemization occurs during the reduction, and optically active 1,2,4-butanetriol is obtained.
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- Nucleic acid derivatives
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A compound which comprises a backbone having a plurality of chiral carbon atoms, the backbone bearing a plurality of ligands each being individually bound to a chiral carbon atom of the plurality of chiral carbon atoms, the ligands including one or more pair(s) of adjacent ligands each containing a moiety selected from the group consisting of a naturally occurring nucleobase and a nucleobase binding group, wherein moieties of the one or more pair(s) are directly linked to one another via a linker chain; building blocks for synthesizing the compound; and rises of the compound, particularly in antisense therapy.
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- A stereoselective and short total synthesis of the polyhydroxylated γ-amino acid (-)-detoxinine, based on stereoselective preparation of dihydropyrrole derivatives from lithiated alkoxyallenes
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Based on our earlier results employing lithiated methoxyallene 2 as C3 building block and imines 3 for the synthesis of dihydropyrrole derivatives 5, we have investigated chiral imines 6, 10, and 15 as electrophilic components. Combined with lithiated alkoxyallenes, these imines provide the corresponding primary adducts and finally the dihydropyrrole derivatives 8, 12, 17, 20, and 22 in good yields and with high to excellent syn selectivities. This stereochemical outcome is interpreted as a result of achelate control. Treatment with hydrochloric acid converted syn-8 and syn-12 into bicyclic compounds 9 and 13, whereas under more mildly acidic conditions adduct syn-17 was transformed into diol syn-18. The total synthesis of the uncommon γ-amino acid (-)-detoxinine could be achieved by starting from (S)-malic acid, which was converted into imine 15 in four steps. Lithiated benzyloxyallene added to imine 15 and efficiently furnished the crucial dihydropyrrole derivative syn-22. The hydrogenolysis of this compound did not directly provide the protected triol 29 as anticipated, but a stepwise protocol made the triol available in a fairly satisfactory manner. A second crucial step of the synthesis was the selective oxidation of 29, which could be achieved by employing platinum dioxide and oxygen. The resulting bicyclic lactone 30 was smoothly transformed into enantiopure (-)-detoxinine. Thus, a fairly short synthesis of this natural product based on a lithiated alkoxyallene could be performed, demonstrating the potential of these intermediates for syntheses of interesting functionalized heterocyclic compounds.
- Floegel, Oliver,Amombo, Marlyse Ghislaine Okala,Reissig, Hans-Ulrich,Zahn, Gernot,Bruedgam, Irene,Hartl, Hans
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p. 1405 - 1415
(2007/10/03)
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- Novel heteroatom-containing vitamin D3 analogs: Efficient synthesis of 1α,25-dihydroxyvitamin D3-26,23-lactam
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Vitamin D3 and its synthetic analogs are promising compounds for controlling various types of cell differentiation. In this article, we describe the synthesis of novel vitamin D3 analogs containing heteroatoms in their side chains - so-called vitamin D3 lactam analogs - via 1,3-dipolar cycloaddition reaction as a key step.
- Kato, Yuko,Hashimoto, Yuichi,Nagasawa, Kazuo
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p. 488 - 499
(2007/10/03)
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- Total synthesis of (+)-phorboxazole A, a potent cytostatic agent from the sponge Phorbas sp.
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A convergent total synthesis of phorboxazole A (1a), from the C(3-19), C(20-27) and C(33-46) fragments 5, 4 and 91, respectively, concentrating on stereocontrolled formation of the bonds at C(2-3), C(19-20) and C(27-28), is described. Although a coupling reaction between a macrolide ketone and the side chain substituted sulfone, at C(27-28) was not successful, a Wadsworth-Emmons olefination involving the oxane methyl ketone 4 and an oxazole produced the oxane 90 which was next coupled to 91 leading to the C(20-46) unit 100. A further coupling of 100 to 71c at C(19-20) then led to 105, ultimately, and the synthesis was completed by a macrocyclisation reaction from 105, at the C(2-3) alkene bond, followed by deprotection of 106.
- Pattenden, Gerald,Gonzalez, Miguel A,Little, Paul B,Millan, David S,Plowright, Alleyn T,Tornos, James A,Ye, Tao
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p. 4173 - 4208
(2007/10/03)
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- Microbial Synthesis of the Energetic Material Precursor 1,2,4-Butanetriol
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The lack of a route to precursor 1,2,4-butanetriol that is amenable to large-scale synthesis has impeded substitution of 1,2,4-butanetriol trinitrate for nitroglycerin. To identify an alternative to the current commercial synthesis of racemic D,L-1,2,4-butanetriol involving NaBH4 reduction of esterified D,L-malic acid, microbial syntheses of D- and L-1,2,4-butanetriol have been established. These microbial syntheses rely on the creation of biosynthetic pathways that do not exist in nature. Oxidation of D-xylose by Pseudomonas fragi provides D-xylonic acid in 70% yield. Escherichia coli DH5α/pWN6.186A then catalyzes the conversion of D-xylonic acid into D-1,2,4-butanetriol in 25% yield. P. fragi is also used to oxidize L-arabinose to a mixture of L-arabino-1,4-lactone and L-arabinonic acid in 54% overall yield. After hydrolysis of the lactone, L-arabinonic acid is converted to L-1,2,4-butanetriol in 35% yield using E. coli BL21(DE3)/pWN6.222A. As a catalytic route to 1,2,4-butanetriol, microbial synthesis avoids the high H2 pressures and elevated temperatures required by catalytic hydrogenation of malic acid. Copyright
- Niu, Wei,Molefe, Mapitso N.,Frost
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p. 12998 - 12999
(2007/10/03)
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- Complete stereochemistry of tetrafibricin
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(Matrix presented) With use of the NMR databases in achiral and chiral solvents, the complete stereochemistry of tetrafibricin (1) has been elucidated without degradation of the carbon framework.
- Kobayashi, Yoshihisa,Czechtizky, Werngard,Kishi, Yoshito
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- Process for the preparation of butane triols
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A process for the preparation of butane triols is provided. In the process, a malic acid diester is reduced with sodium borohydride in the presence of an ether and an alcohol. Preferably, the malic acid diester is an ethyl or methyl ester, the ether is tetrahydrofuran or bis(2-methoxyethyl) ether (diglyme), and the alcohol comprises ethanol. Advantageously, the reaction is carried out at ambient temperature.
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- Process for the preparation of (4R,6S)-4-hydroxy-6-hydroxymethyl-tetrahydropyran-2-one
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The present invention relates to an improved, efficient and enantio-selective process for the synthesis of (4R, 6S)-4-hydroxy-6-hydroxymethyl tetrahydropyran-2-one, employing the Sharpless asymmetric dihydroxylation and regiospecific nucleophilic hydride opening of the cyclic sulfite/sulfate as the key steps. The invention also resides in the intermediates used in the process.
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- Method for producing optically active alcohols
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The invention relates to a process for the preparation of optically active alcohols from optically active carboxylic acids by reducing an optically active carboxylic acid with hydrogen in the presence of a catalyst comprising ruthenium and at least one further metal or transition metal having an atomic number in the range of from 23 to 82.
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- Total synthesis of pederin, a potent insect toxin: The efficient synthesis of the right half, (+)-benzoylpedamide
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A simple and efficient synthesis of (+)-benzoylpedamide, the right half of pederin, was achieved in 16 steps with a 35% overall yield from (S)-malic acid. The key steps include the SmI2-mediated intramolecular Reformatsky reaction, stereoselective allylation, the Sharpless asymmetric dihydroxylation, and amidation. The total synthesis of pederin was accomplished via coupling of the left and right halves.
- Takemura, Takahiro,Nishii, Yoshinori,Takahashi, Shunya,Kobayashi, Jun'ichi,Nakata, Tadashi
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p. 6359 - 6365
(2007/10/03)
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- Spongistatin synthetic studies. An efficient, second-generation construction of an advanced ABCD intermediate
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(formula presented) A short, efficient, and stereocontrolled synthesis of (-)-4, an advanced ABCD subunit of the spongistatins, has been achieved. Central to the synthetic strategy is the multicomponent linchpin union of silyl dithianes with epoxides to access both the AB and CD fragments. Fragment coupling was then achieved via an efficient stereoselective aldol reaction. The linear sequence required 22 steps and proceeded in 4.0% overall yield.
- Smith III, Amos B.,Doughty, Victoria A.,Sfouggatakis, Chris,Bennett, Clay S.,Koyanagi, Jyunichi,Takeuchi, Makoto
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p. 783 - 786
(2007/10/03)
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- Poly(ether-thioether), poly(ether-sulfoxide) and poly(ether-sulfone) nucleic acids
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A compound comprising a poly(ether-thioether), poly(ether-sulfoxide) or poly(ether-sulfone) backbone bearing a plurality of ligands that are individually bound to chiral carbon atoms located within the backbone, at least one of the ligands including a moiety such as a naturally occurring nucleobase, a nucleobase binding group or a DNA interchelator; a process of synthesizing the compound, monomers to be used in this process and their synthesis process and processes for using the compound in biochemistry and medicine.
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- Catalytic enantioselective isomerization of silacyclopentene oxides: New strategy for stereocontrolled assembly of acyclic polyols
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A versatile precursor for the assembly of a range of polyol-containing fragment is the silacyclic alcohol 2 that results from the highly enantioselective, calalytic isomerization of diphenylsilacyclopentene oxide (1). The use of this precursor is illustrated with the efficient and highly diastereoselective assembly of acyclic tetraol motifs.
- Liu, Dong,Kozmin, Sergey A.
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p. 4757 - 4759
(2007/10/03)
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- Synthesis of the H-I-J tricyclic fragment of ciguatoxin, a marine polyether toxin
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During the course of our synthetic studies on ciguatoxin, synthesis of H-I-J tricyclic fragment has been stereoselectively achieved starting from a D-glucal derivative. The key steps are Sonogashira coupling reaction and cobalt complex-mediated oxocane cyclization.
- Liu, Tong-Zhu,Isobe, Minoru
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p. 266 - 268
(2007/10/03)
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- Synthetic studies on the HIJK-ring fragment of ciguatoxin
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Synthesis of the tetracyclic HIJK-ring fragment of ciguatoxin with high stereoselectivity has been achieved starting from a sugar derivative directed toward the synthesis of the right part of ciguatoxin. Sonogashira coupling of a vinyl iodide with an acetylene derivative, cobalt complex-mediated (seven- and eight-membered ring) cyclizations and a heteroconjugate addition reaction play important roles in the current research work. (C) 2000 Elsevier Science Ltd.
- Liu, Tong-Zhu,Isobe, Minoru
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p. 5391 - 5404
(2007/10/03)
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- Asymmetric synthesis of (+)-loline
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The first asymmetric synthesis of (+)-loline has been achieved in 20 steps from (-)-malic acid by a route incorporating intramolecular hetero- Diels-Alder cycloaddition of an acylnitrosodiene.
- Blakemore, Paul R.,Schulze, Volker K.,White, James D.
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p. 1263 - 1264
(2007/10/03)
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- Enantiocontrolled synthesis of trialkyl-substituted stereogenic carbons. A general route to cis-3,5-dialkyl γ-lactones
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(Formula Presented) Lewis acid treatment of tertiary Co2(CO)6-propargylic alcohols having a stereochemically defined benzyloxy group at the γ-benzyl position yielded after cobalt demetalation sec-dialkyl bishomopropargylic alcohols in good yields. The reaction is highly stereoselective and predictable, providing pure stereoisomers. The use of benzyl-α,α′-d2 ethers permitted the stereoselective d-labeling of methines and methylenes. Very simple chemical manipulations provided a general methodology to obtain the enantiomers of 3,5-dialkyl-γ-lactones.
- Díaz, David,Martín, Víctor S.
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p. 335 - 337
(2007/10/03)
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