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  • Sulfoxides  (4)
  • Sigma factors  (2)
  • 1995-1999  (6)
  • 1970-1974
  • 1
    Electronic Resource
    Electronic Resource
    Analysis of cryIAa expression in sigE and sigK mutants of Bacillus thuringiensis (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 734-741 
    Details
    ISSN: 1617-4623
    Keywords: Key words Bacillus thuringiensis ; cry gene expression ; Encapsulation ; Sigma factors ; Sporulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The sigE and sigK genes, encoding the sporulation-specific sigma factors σ35 and σ28 of Bacillus thuringiensis, were each disrupted by inserting a gene conferring resistance to kanamycin into their coding sequence. The B. thuringiensis SigE- and SigK- mutant strains were blocked at different sporulation stages and were unable to sporulate. The SigE- strain was blocked at stage II of sporulation, whereas the SigK- strain was blocked at stage IV. The expression of a cryIAa′-′lacZ transcriptional fusion was analysed in these genetic backgrounds and it was found that both sigma factors are involved in the in vivo transcription of this gene. However, the SigK- strain harbouring the cryIAa gene produced amounts of toxin similar to those produced by the B. thuringiensis Spo+ strain. The toxins accumulated in the mother cell compartment to form a crystal inclusion which remained encapsulated within the cell wall. Thus, transcription from the σE-dependent promoter alone (Bt I promoter) is sufficient to support high levels of toxin production in B. thuringiensis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172985
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis ofcrylAa expression insigE andsigK mutants ofBacillus thuringiensis (1996)
    Springer
    Molecular genetics and genomics 250 (1996), S. 734-741 
    Details
    ISSN: 1617-4623
    Keywords: Bacillus thuringiensis ; cry gene expression ; Encapsulation ; Sigma factors ; Sporulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract ThesigE andsigK genes, encoding the sporulation-specific sigma factorsσ 35 andσ 28 ofBacillus thuringiensis, were each disrupted by inserting a gene conferring resistance to kanamycin into their coding sequence. TheB. thuringiensis SigE− and SigK− mutant strains were blocked at different sporulation stages and were unable to sporulate. The SigE− strain was blocked at stage II of sporulation, whereas the SigK− strain was blocked at stage IV. The expression of acryIAa′-′lacZ transcriptional fusion was analysed in these genetic backgrounds and it was found that both sigma factors are involved in the in vivo transcription of this gene. However, the SigK− strain harbouring thecryIAa gene produced amounts of toxin similar to those produced by theB. thuringiensis Spo+ strain. The toxins accumulated in the mother cell compartment to form a crystal inclusion which remained encapsulated within the cell wall. Thus, transcription from theσ E-dependent promoter alone (Bt I promoter) is sufficient to support high levels of toxin production inB. thuringiensis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02172985
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Enantiomerically Pure 2′,3′,5′-Trideoxy-4′-[(diethoxyphosphoryl)difluoromethyl]thymidine Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2149-2157 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Sulfoxides ; Nucleotide analogues ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: D- and L-(diethoxyphosphoryl)difluoromethyl nucleoside analogues 10 have been synthesized using the building block approach, starting from chiral fluorinated molecules. The key steps of the synthetic sequence were condensation of 2-methyl-5-(4-methylphenylsulfinyl)pent-2-ene (1) and ethyl 2-(diethoxyphosphoryl)-2,2-difluoroacetate (2), reduction of the thus formed ketones 3 to alcohols 4, reductive removal of the sulfur moiety to give hydroxy phosphonates 6, and oxidative cyclization to give furanose derivatives 8.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stereoselective Synthesis of Enantiomerically Pure β-Fluoroalkyl γ-Butyrolactones by Sulfoxide-Directed Lactonization (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 111-115 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Lactones ; Annulation ; Ketene ; Sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Enantiomerically pure α,α-dichloro β-fluoroalkyl γ-p-tolylthio γ-butyrolactones trans-6a-c have been obtained with excellent stereocontrol (〉 98:2) and enantiomeric purity (〉 98:2) by sulfoxide-directed lactonization (Marino's annu-lation reaction) of β-fluoroalkyl vinyl sulfoxides (R)-(E)-5a-c with dichloroketene. Highly chemoselective dechlorination and desulfurization reactions performed on trans-6c efficiently provided the β-chlorodifluoromethyl γ-butyrolactone (S)-8c, the absolute stereochemistry of which was determined by X-ray diffraction analysis of its γ-p-tolylthio precursor (2R,3S)-7c.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Stereoselective Synthesis of the Pheromone (R)-(-)-Sulcatol, and Its Enantiopure (R)- and (S)-1-Mono-, -1,1-Di-, and -1,1,1-Trifluoro Analogues[1] (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 117-127 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Pheromones ; Sulfoxides ; Sulcatol ; Asymmetric synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The pheromone (R)-(-)-sulcatol (10a) and three of its enantiomeric mono-, di-, and trifluoro analogues 10b-d have been synthesized, in six steps and with good overall yields, starting from chiral (R)-2-methyl-5-[(4-methylphenyl)sulfinyl]pent-2-ene (1) and commercially available fluorinated or non-fluorinated acetates.Supporting information for this article is available on the WWW under http://www.wileY-Vch.de/contents/jc_2046/1999/98375_s.pdf or from the author.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Stereoselective Synthesis of Fluorinated Isoxazolidines and 2,3-Dihydroisoxazoles: A Cycloadditive Route to Enantiomerically Pure Amino Fluoro Alcohols (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1665-1670 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine ; Cycloadditions ; Nitrones ; Asymmetric induction ; Sulfoxides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-(Fluoroalkyl)isoxazolidines 6 and -2,3-dihydroisoxazoles 8 have been obtained in enantiomerically pure form with good diastereoselectivity by 1,3-dipolar cycloaddition of diethyl fumarate and dimethylacetylene dicarboxylate, respectively, to the chiral fluorinated nitrone (R)-5. The latter has been prepared from the β-fluoromethyl-β-oxo sulfoxide (RS)-1, by a synthetic sequence where the chiral and enantiomerically pure sulfinyl function acts as a removable source of chirality. Reductive opening of isoxazolidines 6 then afforded amino fluoromethyl diols 7 in good yields.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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