- Stereochemical elucidation of streptorubin B
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Streptorubin B is a structurally remarkable mem-ber of the prodiginine group of antibiotics produced by several actinobacteria, including the model organism Streptomyces coelicolor A3(2). Transannular strain within the pyrrolophane structure of this molecule causes restricted rotation that gives rise to the possibility of (diastereomeric) atropisomers. Neither the relative nor the absolute stereochemistry of streptorubin B is known. NOESY NMR experiments were used to define the relative stereochemistry of the major atropisomer of streptorubin BHCl in solution as anti. We exploited this finding together with our knowledge of streptorubin B biosynthesis in S. coelicolor to determine the absolute stereochemistry of the anti atropisomer. 2-Undecylpyrrole stereoselectively labeled with deuterium at C-4′ was synthesized and fed to a mutant of S. coelicolor, which was unable to produce streptorubin B because it was blocked in 2-undecylpyrrole biosynthesis, and in which the genes responsible for the last two steps of streptorubin B biosynthesis were overexpressed. 1H and 2H NMR analysis of the stereoselectively deuterium-labeled streptorubin BHCl produced by this mutasynthesis strategy allowed us to assign the absolute stereochemistry of the major (anti) atropisomer as 7′S. HPLC analyses of streptorubin B isolated from S. coelicolor on a homochiral stationary phase and comparisons with streptorubin B derived from an enantioselective synthesis showed that the natural product consists of an approximately 88:7:5 mixture of the (7′S, anti), (7′S, syn), and (7′R, anti) stereoisomers.
- Haynes, Stuart W.,Sydor, Paulina K.,Corre, Christophe,Song, Lijiang,Challis, Gregory L.
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p. 1793 - 1798
(2011/04/12)
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- Combination of novozym 435-catalyzed hydrolysis and mitsunobu reaction for production of (r)γ-lactones
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Chiral-lactones of both enantiomers were synthesized with more than 90% optical purities. The key step was Novozym 435-catalyzed hydrolysis of racemic N-benzyl-4-acetoxyalkylamides. Additionally, because (R)-γ-lactones are predominant in apricot, mango, peach, passion fruit, and strawberry, synthesis was attempted using only one enantiomer selectively. The (R)-enantimer was synthesized with more than 80% total yield and more than 90% optical purity by a combination of Novozym 435-catalyzed hydrolysis and the Mitsunobu reaction. Copyright
- Shimotori, Yasutaka,Miyakoshi, Tetsuo
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experimental part
p. 1607 - 1613
(2010/06/21)
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- Synthesis of (S)-γ- lactones with a combination of lipase-catalyzed resolution and mitsunobu reaction
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Six kinds of (S) - lactones [e.g., (S) - decalactone, (S) - undecalactone, and (S) - jasmolactone] were synthesized with 71-88% yields and 97% optical purities by combining lipase-catalyzed resolution with the Mitsunobu reaction. Copyright Taylor & Francis Group, LLC.
- Shimotori, Yasutaka,Miyakoshi, Tetsuo
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experimental part
p. 1570 - 1582
(2009/11/30)
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- Gamma-Undecenolactone, Method for the Preparation and Use Thereof for Cosmetics and in the Form of Food Additives
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The invention relates to a gamma-undecenolactone of formula (I), wherein a lactonic cycle can carry an unsaturation between carbon No2 and carbon No3 and is preferably saturated, RI is a possibly substituted C7 alkenyl or alkynyl group comprising at least one unsaturation, and preferably RI is an CH2═CH—CH2—CH2—CH2—CH2—CH2 group, said gamma-undecenolactone contains an asymmetric carbon in position 4 having (R) or (S) configuration. The biosynthesis of said gamma-undecenolactone and the use thereon for perfumery and for a food flavouring agent are also disclosed.
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Page/Page column 5
(2008/12/05)
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- Facile synthesis of optically active γ-lactones via lipase-catalyzed reaction of 4-substituted 4-hydroxybutyramides
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Lipase-catalyzed transesterification of racemic 4-substituted 4- hydroxybutyramides with succinic anhydride proceeded enantioselectively to afford (S)-succinic acid monoester and unreacted (R)-4-hydroxybutyramide derivative, which were separated easily by
- Matsumura, Yasufumi,Endo, Teruko,Chiba, Mitsuo,Fukawa, Hidemichi,Terao, Yoshiyasu
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p. 304 - 305
(2007/10/03)
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- A convenient chiral synthesis of 4-alkyl-γ-butanolides
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A simple three step synthesis of 4-alkyl-γ-butanolides as flavoring compounds from chiral propargyl alcohols is described.
- Yadav,Maniyan
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p. 2731 - 2741
(2007/10/02)
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- Lipase-catalyzed Transesterification in organic Solvents: Preparation and Enantiodifferentiation of optically enriched 4(5)-alkylated 1,4(1,5)-olides
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Porcine pancreatic lipase (PPL) catalyzed intramolecular transesterification of n-propyl esters of 4(5)-hydroxyalkanoic acids (C5-C12) in diethyl ether (20 deg C) yielded (S)-4-alkylated 1,4-olides of high optical purity (ee > 80percent) and optically pure (R)-4-hydroxyalkanoic-n-propylesters, but exhibited low enantioselectivity for (S)-5-alkylated 1,5-olides (ee=10-20percent).The chiral analysis of 4(5)-hydroxyalkanoic esters was performed by HRGC and HPLC after their derivatization with (R)-(+)-1-phenylethylisocyanate, (S)-O-acetyllactic acid chloride, and (R)-(+)-α-methoxy-α-trifluoromethylphenylacetic acid chloride.The enantiodifferentiation of 1,4(1,5)-olides was achieved by HPLC on a chiral (ChiraSpher) using an on-line optical rotation detector (ChiraMonitor).
- Huffer, Manfred,Schreier, Peter
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p. 1157 - 1164
(2007/10/02)
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- ENZYMATIC RESOLUTION OF RACEMIC LACTONES
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PPL, HLE or PLE enzymatic resolution of racemic γ, δ and ε-lactones gives optically active lactones (ee: 60 to 90percent).
- Blanco, L.,Guibe-Jampel, E.,Rousseau, G.
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p. 1915 - 1918
(2007/10/02)
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- Synthesis of the optical antipodes of 4-alkyl-γ-lactones
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Optical antipodes of 4-alkyl-γ-lactones 3 have been prepared by photochemical rearrangement of optically active α,β-epoxy diazomethyl ketones 1 in ethanol to give 4-hydroxy-alkenoates 2, followed by reduction of the alkene bond and subsequent lactonization.The required epoxy diazomethyl ketones 1 were obtained via the following sequence of reactions: alkylation of 2-propyn-1-ol, subsequent reduction to the alkenols 6, Sharpless epoxidation to 2,3-epoxy alcohols 7, oxidation to glycidic esters 8 and finally conversion to diazo ketones 1.The enantiomeric purities range from 84 to 100percent.
- Thijs, Lambertus,Waanders, Peter P.,Stokkingreef, Edwin H. M.,Zwanenburg, Binne
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p. 332 - 337
(2007/10/02)
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- KINETIC RESOLUTION OF LACTONES BY ENANTIOSELECTIVE PROTONATION OF THE CORRESPONDING CARBOXYLATE WITH A CHIRAL ACID
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Racemic lactones were optically activated through the hydrolysis with sodium hydroxide followed by the partial neutralisation with (1S)-(+)-10-camphorsulfonic acid in ethanol to afford R- or S-isomer with 99 - 38percent ee.
- Fuji, Kaoru,Node, Manabu,Murata, Makoto,Terada, Shunji,Hashimoto, Keiji
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p. 5381 - 5382
(2007/10/02)
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