- Baeyer–Villiger monooxygenase-catalyzed desymmetrizations of cyclobutanones. Application to the synthesis of valuable spirolactones
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A series of γ-butyrolactone derivatives, including some spiranic ones, was obtained through desymmetrization of the corresponding prochiral 3-substituted cyclobutanones via Baeyer–Villiger monooxygenase (BVMO)-catalyzed oxidation. After reaction optimization using several commercial enzymes, both antipodes of various lactones were synthesized in most cases with >90% conversion and >80% enantiomeric excess under mild reaction conditions. In some cases alcohol formation was also observed (up to 40% conversion) as an undesired side reaction due to the presence of alcohol dehydrogenases in these preparations. Selected transformations were achieved on a 100 mg scale showing the possibilities of these oxidative biocatalysts as a new source of highly interesting compounds.
- Rodríguez-Mata, María,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,García-Cerrada, Susana,Mendiola, Javier,de Frutos, óscar,Collado, Iván
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supporting information
p. 7268 - 7275
(2016/10/26)
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- Efficient and Selective Cu/Nitroxyl-Catalyzed Methods for Aerobic Oxidative Lactonization of Diols
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Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
- Xie, Xiaomin,Stahl, Shannon S.
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p. 3767 - 3770
(2015/04/14)
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- β-Pseudopeptide foldamers. the homo-oligomers of (4R)-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid (D-Oxac)
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A total synthesis in solution and a conformational analysis of the homo-oligomers of (4R)-(2-oxo-1,3-oxazolidin-4-yl)-acetic acid (D-Oxac) to the tetramer level are described. As the D-Oxac building block contains both an oxazolidin-2-one and a β-amino acid group, it may represent a new type of conformationally constrained tool for the construction of β-pseudopeptide foldamers. A conformational investigation using NMR and an extensive, unconstrained analysis with a Monte Carlo search to the octamer level, both in water and in chloroform, showed that these homo-oligomers tend to fold in a regular helical structure in a competitive solvent, such as water. Since aqueous solutions are of major relevance for biological systems, these molecules are good candidates for application to these environments.
- Luppi, Gianluigi,Galeazzi, Roberta,Garavelli, Marco,Formaggio, Fernando,Tomasini, Claudia
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p. 2181 - 2187
(2007/10/03)
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- Studies towards the total synthesis of batzelladine A
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Application of a diastereoselective three-component coupling to the bicyclic core of the batzelladine alkaloids is described. The synthesis features the elaboration of glutamic acid by use of Eschenmoser sulfide contraction. An earlier approach is also included, which shows some limitations of dithiane chemistry when applied to the particular compounds required for this target.
- Elliott, Mark C.,Long, Matthew S.
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p. 2003 - 2011
(2007/10/03)
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- A new entry to polyfunctionalized 4,5-trans disubstituted oxazolidin-2-ones from L-aspartic acid
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A straightforward synthesis of enantiomerically pure (4R,5S)-5-oxazolidinecarboxylic acid, 2-oxo-4-[(t-butyldimethyl-silyloxy)methyl]-, benzyl ester and of (4S,5S)-4-oxazolidinecarboxylic acid, 2-oxo-5-[(t-butyldimethylsilyloxy)methyl]-, benzyl ester was envisaged starting from readily available L-aspartic acid. The key step is the diastereoselective addition of iodine with the introduction of a new stereogenic centre.
- Luppi, Gianluigi,Tomasini, Claudia
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p. 797 - 800
(2007/10/03)
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- NOVEL BETA-LACTAM COMPOUNDS AND PROECSS FOR PRODUCING THE SAME
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1. A β-lactam compound of the formula [1]; ???wherein R1 is a lower alkyl, a lower alkyl substituted by a hydroxy; R2 is a hydrogen, a lower alkyl; X is O, S, NH; m and n are 0 to 4, Y1 is a halogen, cyano, a hydroxy, an amino, a lower alkyloxy, a lower alkylamino, a carboxy, a carbamoyl, a lower alkyl, etc., Y2 is hydrogen, an alkyl, cyano, -C(R3)=NR4 (wherein R3 and R4 are hydrogen, an amino, an alkyl, etc., or R3 and R4 may combine each other together with the nitrogen atom to form a 5- to 7-membered heterocyclic group), or a pharmaceutically acceptable salt thereof, or a non-toxic ester thereof, which has an excellent antibacterial activity against Gram-positive bacteria, especially against MRSA and MRCNS.
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- Introduction of 4(S)-oxazolidineacetic acid, 2-oxo (D-Oxac) motif in a polypeptide chain: Synthesis and conformational analysis
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A four step synthesis of 4(S)-oxazolidineacetic acid, 2-oxo benzyl ester (D-Oxac-OBn) from L-Asp-OH in 45% overall yield is reported. The formation of by-products is completely avoided, by microwave irradiation and by the use of caesium carbonate as base. Moreover the synthesis and IR and 1H NMR conformational analysis of the tetramers Boc-L-Val-D-Oxac-L-Ala-OBn and Boc-L-Val-D-Oxac-Aib-L-Ala-OBn in solution is reported.
- Luppi, Gianluigi,Villa, Marzia,Tomasini, Claudia
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p. 247 - 250
(2007/10/03)
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- Facile and chemoselective reduction of carboxylic acids to alcohols using BOP reagent and sodium borohydride
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Hydroxybenzotriazolyl esters, formed in situ from carboxylic acids and BOP reagent, react with sodium borohydride in THF to give alcohols in high yields. This method is convenient, rapid and chemoselective, with such functional groups as nitro, halide, nitrile, azido and ester being unaffected.
- McGeary, Ross P.
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p. 3319 - 3322
(2007/10/03)
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- New nodularins: A general method for structure assignment
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A general method has been developed for assigning the structures of nodularin, a potent hepatotoxin, tumor promoter, and protein phosphatase inhibitor, and minor components isolated from a cultured and a bloom sample of the cyanobacterium Nodularia spumigena. It consists of (1) FABMS analysis (determination of molecular weight and molecular formula), (2) 1H NMR spectroscopy on the parent compound and chiral GC analysis of an acid hydrolyzate (identification and stereochemistry of amino acid components), (3) ozonolysis followed by NaBH4 reduction (conversion to a linear peptide), and (4) FABMS/CID/MS analyses of the linear peptide and the parent compound (sequence analysis). The method has been employed in assigning structures to three new nodularins (2-4) and can be applied to other cyclic peptides containing α,β-dehydroamino acid unit(s), especially the related microcystins, cyclic heptapeptide hepatotoxins. Two nodularins, [DMAdda3]nodularin (2) and [(6Z)Adda3]nodularin (3), were obtained from a bloom sample collected from Lake Ellesmere (New Zealand), and [D-Asp1]nodularin (4) was isolated from cultured cells (strain L-575). The LD50s of 2 and 4 were 150 and 75 μg/kg (ip, mice), respectively, but 3 did not show apparent toxicity at 2.0 mg/kg.
- Namikoshi,Choi,Sakai,Sun,Rinehart,Carmichael,Evans,Cruz,Munro,Blunt
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p. 2349 - 2357
(2007/10/02)
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- A facile synthesis of chiral N-protected β-amino alcohols
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Chiral N-protected β-amino alcohols are easily obtained by NaBH4 reduction of mixed anhydrides of N-protected α-amino acids in an organic/aqueous medium. The alcohols obtained from side chain or main chain reduction of N-protected aspartic acid are converted in good yields into lactones.
- Rodriguez,Llinares,Doulut,Heitz,Martinez
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p. 923 - 926
(2007/10/02)
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- Synthesis of 3-Methoxy-2-iso-oxacephalosporin
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Optically active 3-methoxy-2-iso-oxacephalosporins are efficiently prepared via intramolecular acylation as a key step.
- Nitta, Hajime,Hatanaka, Minoru,Ueda, Ikuo
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p. 432 - 433
(2007/10/02)
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- DEVELOPMENT OF CHIRAL β-DICARBONYL EQUIVALENTS. ENANTIODIVERGENT ALKYLATION OF ASPARTIC ACID.
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L-Aspartic acid has been converted to derivatives which undergo alkylation reactions with stereoselectivities that are enantiomerically complimentary.
- McGarvey, Glenn J.,Hiner, Roger N,Matsubara, Yoshio,Oh, Taeboem
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p. 2733 - 2736
(2007/10/02)
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