• Korean Journal of Microbiology
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• v.38 no.4
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• pp.245-245
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• 2002

Catabolic pathways for the degradation of various aromatics by Sphingomonas yanoikuyae Bl are intertwined, joining at the level of substituted benzoates, which are further degraded vita ring cleavage reactions. The mutant strain EK497, which was constructed by deleting a large DNA region containing most of the genes for biphenyl, naphthalene, m-xylene, and m-toluate degradation, was unable to grow on all of the aromatics tested except for benzoate as the sole source of carbon and energy.S. yanoikuyae EK497 was found to possess only catechol ortho-ring cleavage activity due to deletion of the genes for the meta-cleavage pathway. Wild-type S. yanoikuyae Bl grown on benzoate has both catechol orthoand meta-cleavage activity. However, m-xylene and m-toluate, which are metabolized through methylbenzoate, and biphenyl, which is metabolized through benzoate, induce only the meta-cleavage pathway, suggesting the presence of a substrate-dependent induction mechanism.

• Bulletin of the Korean Chemical Society
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• v.24 no.2
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• pp.256-258
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• 2003

• Bulletin of the Korean Chemical Society
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• v.31 no.8
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• pp.2135-2136
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• 2010

• Journal of Microbiology
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• v.38 no.4
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• pp.245-249
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• 2000

Catabolic pathways for the degradation of various aromatics by Sphingomonas yanoikuyae Bl are intertwined, joining at the level of substituted benzoates, which are further degraded vita ring cleavage reactions. The mutant strain EK497, which was constructed by deleting a large DNA region containing most of the genes for biphenyl, naphthalene, m-xylene, and m-toluate degradation, was unable to grow on all of the aromatics tested except for benzoate as the sole source of carbon and energy.S. yanoikuyae EK497 was found to possess only catechol ortho-ring cleavage activity due to deletion of the genes for the meta-cleavage pathway. Wild-type S. yanoikuyae Bl grown on benzoate has both catechol orthoand meta-cleavage activity. However, m-xylene and m-toluate, which are metabolized through methylbenzoate, and biphenyl, which is metabolized through benzoate, induce only the meta-cleavage pathway, suggesting the presence of a substrate-dependent induction mechanism.

• Bulletin of the Korean Chemical Society
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• v.21 no.6
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• pp.595-603
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• 2000

Ring expansion reactions via endocyclic cleavage of cyclopropylcarbinyl radicals derived from the reaction of [1-benzyloxycarbonylbicyclo[n. 1.O]alk-(n+l)-yl] -1-imidazolethiocarboxylates with tributyltin hydride/AIBN proceeded to produce 3-cycloalkenecarboxylates in good yields. Benzyl (5'-phenoxypentyl) -3-cyclohepten-1 -carboxylate was obtained in 33% yield from the reaction of benzyl 5-methylenebicyclo [4. 1.0]- 1-carboxylates with 4-phenoxybutyl iodide under radical conditions. Selective cleavage of endocyclic bond in cyclopropane to the cyclohexane, results from stabilization of the resultant radical by the carbonyl groups, such as the benzyloxycarbonyl group, which lower the transition state energy for the final cyclopropane cleavage in the ring expansion.

• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.674-678
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• 1991

Methanolysis of a ${\beta}$-lactam ring of a cephalosporin was simulated with AM1 semiempirical quantum mechanical calculation. The tetrahedral intermediate TD1 from an O-protonated cephalosporin and a methanol transfers the proton intramolecularly to the C-4 carboxylate to generate an oxyanion, i.e., second tetrahedral intermediate TD2, which undergoes the amide bond cleavage without further protonation on the N-5. For this cleavage a low-energy barrier TS2 was located. According to the energy diagram, tetrahedral intermediates easily undergo ring cleavage even without the protonation on the amide nitrogen.

• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.71-78
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• 1988

The crown ether ring of 20, 21, 24, 25-tetranitrodibenzo-18-crown-6(TNDB-18-C-6) was cleaved by various alcoholic bases to give 2,4,5-trialkoxynitrobenzene derivatives and 4,5-dialkoxy-1,2-dinitrobenzene derivatives as the major products, and bis[(alkoxynitrophenoxy)ethyl]ether derivatives from partially cleaved crown ether ring as the minor products. The ring cleavage reaction of TNDB-18-C-6 with ethylene glycolic base resulted ring contraction through intramolecular nucleophilic cyclization of the initially formed ring cleavage product to give nitro derivatives of DB-14-C-4.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.766-771
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• 2004

Julong 601, a Gram-positive anaerobic bacterium strain capable of cleaving the C-ring of isoflavones daidzein and genistein, was isolated from human feces. BLAST search revealed that its complete 16S rDNA gene sequence has 99% similarity to Eubacterium ramulus. Metabolites of daidzein and genistein were determined as O-desmethylangolensin (O-Dma) and 2-(4-hydroxyphenyl) propionic acid (2-HPPA), respectively, based on UV, EI-MS, and $^1H$ and ^{13}C$ NMR spectral analyses. Enantiomers of O-Dma and 2-HPPA were isolated by chiral stationary-phase HPLC (CSP HPLC). Cleavage of the C-ring of daidzein and genistein by strain Julong 601 was highly enantioselective. Specific rotation ([$\alpha]_D$) and circular dichroism (CD) spectra of the enantiomers are reported here for the first time. Biotransformation kinetics of daidzein and genistein indicated that the C-ring of genistein has a higher susceptibility to bacterial degradation than that of daidzein.

• Mass Spectrometry Letters
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• v.4 no.4
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• pp.79-82
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• 2013

Various types of alkaloids observed in several herbal medicines were analyzed by electrospray ionization tandem mass spectrometry in positive ion mode. In the present study, MS/MS spectralpatterns were investigated for eight-types of alkaloids (aporpine, protoberberine, tetrahydroprotoberberine, benzylisoquinoline, protopine, phthalide, morpine, and bisbenzylisoquinoline). For aporpine- and protoberberine-type alkaloids, main fragmentations occurred at substituted groups on rigid ring structures, not showing ring fusion. Interesting fragmentations due to iminolization and retro-Diels-Alder (RDA) reaction were observed in MS/MS spectra of protopine- and tetrahydroprotobereberine-type alkaloids. Also, several types of fragmentations such as inductive cleavage and ${\alpha}$-cleavage, or bond cleavage between two ring structures were observed depending on their structural characteristics. These fragmentation patterns are expected to allow instant classification of the specific alkaloid type in various MS/MS spectra of alkaloids.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2823-2824
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• 2009