• 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.

• Archives of Pharmacal Research
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• v.15 no.3
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• pp.234-238
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• 1992

Using cell-free extract of Lysobacter lactamgenus, enzymatic conversion of $\delta$-L-($\alpha$-aminoadiphyl)-L-cysteinyl-D-valine (ACV) the first substrate of $\beta$-lactam biosynthesis, into antibiotic compounds was attempted. In high performance liquid chromatographic (HPLC) analysis, the biosynthetic intermediates for cephalosporin antibiotics including isopenicillin N, deacetoxycephalosporin C, deacetylcephalosporin C and unknown cephem compound were detected in reaction mixtures. It implies that cephabacin compounds from L lactamgenus could be produced by biosynthetic routes through penicillin ring formation and its expansion to cephalosporin ring, likely as cephalosporin C from Cephalosporium or cephamycin C from Streptomyces. Among biosynthetic enzyme in cell-free extract, the ring formation activity (isopenicillin N synthetase activity) was separated in 50-60% of ammonium sulfate fraction, and ring expansion activity (deacetoxycephalosporin C synthetase activity) was found to be in 40-50% fraction. The partially purified isopenicillin N synthetase could convert as much as 90% ACV to isopenicillin N during 6-hour reaction.

• The Korean Journal of Pesticide Science
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• v.9 no.3
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• pp.185-190
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• 2005

Solid phase synthesis of 16, which is a derivative of the first systemic fungicide, carboxin 1 was described. Reaction of 1,3-oxathiolane derivative with solid resin of 4-hydroxy-3-nitrobenzophenone 6 gave 9 in 82% yield. Oxidation of sulfur in the solid 1,3-oxathiolane 9 by MCPBA followed by a ring expansion reaction under the acid catalyst afforded the corresponding dihydro-1,4-oxathiin derivative 12. Treatment of the solid 1,3-oxathiolane 9 with p-methoxyaniline resulted in 1,3-oxathiolane 14, 1,3-oxathiolane sulfoxide 15, dihydro-1,4-oxathiin 16, and acetoacetanilide derivative 17 in 41%, 35%, 14%, 10% yields, respectively.

• YAKHAK HOEJI
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• v.27 no.3
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• pp.185-205
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• 1983

Penicillins and cephalosporins are biosynthesized from L-.alpha.-aminoadipic acid, L-cysteine and L-valine. A tripeptide, LLD-$\delta$-($\alpha$-aminoadipyl)cysteinylvaline(LLD-ACV) was isolated from fermentation broths of Cephalosporium acremonium as well as of Penicillium chrysogenum and it was proved that the LL-$\delta$-($\alpha$-aminoadipyl cysteine was formed first in mycelia, to which valine would be connected to give LLD-ACV. However, several points are still unsolved; first, what mechanism is involved in the configurational change from L-valine to D-valine, second, what kind of cyclization mechanism gives a $\betha$-lactam ring and a thiazolidine ring and third, what is the pathways for the ring expansion from penicillins to cephalosporins. At present, it seems clear that LLD-ACV is cyclized to give isopenicillin N, which is transformed to penicillin N and further to cepbalosporin C. Other hydrophobic penicillins, including benzyl penicillin and penicillin V, are formed from isopenicillin N by acyl-exchange reactions catalyzed by penicillin transferase, rather than by acylation reaction on 6-aminopenicillanic acid(6-APA), which was isolated from the fermentation broth of P. chrysogenum and which would be formed by hydrolysis of $\delta-(\alpha$-amincadipyl)amido moiety at the C-6 position in isopenicillin N or penicillin N by penicillin acylase. Acylation of 6-APA is catalyzed also by penicillin acylase, but the reaction is proved not to be involved in penicillin biosynthesis. Understanding the biosynthesis of penicillins and cephalsoporins would provide solutions to increase in fermentation yields of penicillins, especially of cephalosporins and a solution to biological production of 7-aminocepbalosporanic acid (7-ACA) which is of importance in pharmaceutical industry. Still regulation mechanisms in penicillin and cephalosporin biosynthesis are unveiled at all.

• Bulletin of the Korean Chemical Society
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• v.13 no.1
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• pp.83-87
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• 1992

The ring expansion of 1,3-thiazolidines 4 derived from ${\beta}$-ketoacid derivatives to the corresponding dihydro-1,4-thiazines 1 by using the action of chlorine on 4 has been achieved. In the chlorinolysis unisolable sulfenyl chlorides 5 may be formed from chlorosulfonium ions 11 by ${\beta}$-elimination involving carbonyl activated methylene hydrogens. Addition of sulfenyl chloride to the internal double bond appears to form probable thiiranium ions 14, which in turn gave 1 with loss of acidic proton. Imminium ions 15 could be hydrolyzed easily to give enol 8. As a side reaction, dihydrothiazine that was formed was further chlorinated to produce dichlorides 16 which were rearranged readily to the chloromethyl compounds 10.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.337-353
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• 2016

The successful completion of the present research would be achieved using ground waste glass (GWG) microparticles in self-consolidating concrete (SCC). Here, the influences of GWG microparticles as cementing material on mechanical and durability response properties of SCC are investigated. The aim of this study is to investigate the hardened mechanical properties, percentage of water absorption, free drying shrinkage, unit weight and Alkali Silica Reaction (ASR) of binary blended concrete with partial replacement of cement by 5, 10, 15, 20, 25 and 30 wt% of GWG microparticles. Besides, slump flow, V-funnel, L-box, J-ring, GTM screen stability, visual stability index (VSI), setting time and air content tests were also performed as workability of fresh concrete indicators. The results show that the workability of fresh concrete was increased by increasing the content of GWG microparticles. The results showed that using GWG microparticles up to maximum replacement of 15 % produces concrete with improved hardened strengths. From the results, when the amount of GWG increased there was a gradual decrease in ASR expansion. Results showed that it is possible to successfully produce SCC with GWG as cementing material in terms of workability, durability and hardened properties.

• Journal of the Korean Chemical Society
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• v.33 no.2
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• pp.247-256
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• 1989

4-Acetyl-5,6-dihydro-2-methyl-1,4-thiazine carboxylic acid derivatives 24 were prepared by ring expansion of corresponding thiazolidine sulfoxides. Oxidation of 2-methyl-1,3-thiazolidine-2-acetic acid derivatives 12 gave a mixture of cis and trans sulfoxides, 14 and 15. Assignments of the cis and trans sulfoxides were based on the $^1HNMR$ and IR spectroscopy and regioselectivity of deuterium exchange reaction. With PTSA as acid catalyst both the cis and trans sulfoxide, 14 and 15 were transformed via sulfenic acid 18 to dihydro-1,4-thiazine 24. However, under the neutral conditions (in DMF at $100^{\circ}C$) the trans sulfoxides 15 rearranged via sulfenic acid 21 to isomeric dihydrothiazines 27. The mechanism of formations of 24 and 27 is also discussed.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.309-315
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• 2024

Silicon and carbon composite (SiC) is considered one of the most promising anode materials for the commercialization of Si-based anodes, as it could simultaneously satisfy the high theoretical capacity of Si and the high electronic conductivity of carbon. However, SiC active material undergoes repeated volumetric changes during charge/discharge processes, leading to continuous electrolyte decomposition and capacity fading, which is still considered an issue that needs to be addressed. To solve this issue, we suggest a 4,4'-Methylenebis(cyclohexyl isocyanate) (H₁₂MDI)-based waterborne polyurethane binder (HPUD), which forms a 3D network structure through thermal cross-linking reaction. The cross-linked HPUD (denoted as CHPU) was prepared using an epoxy ring-opening reaction of the cross-linker, triglycidyl isocyanurate (TGIC), via simple thermal treatment during the SiC anode drying process. The SiC anode with the CHPU binder, which exhibited superior mechanical and adhesion properties, not only demonstrated excellent rate and cycling performance but also alleviated the volume expansion of the SiC anode. This work implies that eco-friendly binders with cross-linked structures could be utilized for various Si-based anodes.

• Journal of the Korean Chemical Society
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• v.37 no.1
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• pp.119-130
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• 1993

The stereochemistry of 1,3-thiazolidine sulfoxides 1 in which 3 chiral centres are present in a molecule was elucidated by deuterium exchange and trapping reactions. 3-Acetoxy-1,3-thiazolidines 5 was oxidized to 6 and 8, corresponding $\alpha$-cis 10, $\alpha$-trans 11, $\beta$ -cis 12, and $\beta$ -trans 13 isomers were separated from their diasteromeric mixtures. Sulfoxide 10 was isomerized to more thermodynamically stable isomer 13 under neutral conditions in refluxing benzene or toluene. The methyl hydrogens of 2-methyl group in the sulfoxide 13 and those of the sulfoxide 11 were deuterated by the deuterium incorporation reactions. The intermediate sulfenic acids 25 and 26 derived from the sulfoxides 10 and 12 via sigmatropic rearrangement were trapped by 2-mercaptobenzothiazole (2-MBT) to give disufides 27 and 28 respectively. However, the sulfoxides 11 and 13 were transformed to ring expansion product dihydro-1,4-thiazine 29 under the same reaction conditions. In the presence of acid catalyst, the sulfoxides 10, 11, and 12 were converted to dihydro-1,4-thiazine 29 through the sulfoxide 13 quantitatively. The mechanisms of isomerization of sulfoxides and the formation of 29 were also discussed.