• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.1996-1998
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• 2014

Licochalcone C was synthesized from commercially available 2,4-dihydroxybenzaldehde by using regioselective $Al_2O_3$-mediated C-prenylation followed by conventional Claisen-Schmidt condensation in basic condition.

• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.976-980
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• 2006

The synthesis of 4'-phenyl and 1'-methyl doubly branched carbocyclic nucleoside was accomplished from 2-hydroxy acetophenone. The 4'-phenyl group was installed via a [3,3]-sigmatropic rearrangement reaction, and the carbonyl addition of methylmagnesium bromide was used to introduce the 1'-methyl group. Cyclization of divinyl 9 was performed using $2^{nd}$ generation Grubbs catalyst. The coupling of cyclopentenol 12$\alpha$ with 6-chloropurine by Mitsunobu reaction and desilylation was used to synthesize the target nucleoside 15.

• Archives of Pharmacal Research
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• v.29 no.6
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• pp.464-468
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• 2006

Novel phenyl branched apiosyl nucleosides were synthesized in this study. The introduction of phenyl group in the 4'-position was accomplished by a [3,3]-sigmatropic rearrangement. Apiosyl sugar moiety was constructed by sequential ozonolysis and reductions. The natural bases (cytosine and adenine) were efficiently coupled with an apiosyl sugar by classical glycosyl condensation procedure (persilyated base and TMSOTf). The antiviral activities of the synthesized compounds were evaluated against the HIV-1, HSV-1, HSV-2 and HCMV.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.243.1-243.1
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• 2003

Extensive efforts in the search of therapeutically useful carbocyclic nucleosides have resulted in a wealth of their synthetic methodologies in racemic and optically active forms. The classical one-directional methods such as linear synthesis and convergent synthesis are the approaches most frequently seen in the literature for the preparation of carbocyclic nucleosides, and their advantages and limitations are well known. (omitted)

• Journal of the Korean Chemical Society
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• v.30 no.6
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• pp.548-552
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• 1986

A stereoselective synthesis of 3-phenoxybenzyl (${\pm}$)-cis and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid starting from readily available 2-methyl-3-buten-2-ol($\underline{2}$) is described. Allylic rearrangement of 2-methyl-3-buten-2-ol, in the presence of acetic acid and acetic anhydride gave 3-methyl-2-butenyl acetate($\underline{3}$). The [3,3] sigmatropic rearrangement of the allyl acetate($\underline{3}$), as the silylketene acetal, produced the ${\gamma},\;{\delta}$-unsaturated acid($\underline{4}$). Treatment of 3,3-dimethyl-4-pentenoic acid($\underline{4}$) with SOCl2 followed by esterification with 3-phenoxybenzyl alcohol yielded 3, 3-dimethyl-4-pentenoic acid ester($\underline{5}$). Addition of carbon tetrachloride to the olefin ester($\underline{6}$) furnished 4,6,6,6-tetrachloro-3,3-dimethylhexanoic acid ester ($\underline{7}$). Cyclization with potassium t-butoxide and elimination of hydrogen chloride afforded 3-phenoxybenzyl (${\pm}$) cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethyl-1-cyclopropanecarboxylic acid.

• Journal of the Korean Chemical Society
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• v.27 no.1
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• pp.38-45
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• 1983

Aziridine derivatives were utilized for the formation of aziridine N-oxides at low temperature, which were subject to easy decomposition and/or rearrangement like the protonated aziridines at room temperature. t-Butyl nitroso compound formed by the decomposition of N-oxide is easily characterized by its blue color and it is the major product in case that no branched alkyl groups are substituted on the carbon atoms of the aziridine ring and the stationary groups on the nitrogen are inert to rearrange the oxide such as the t-butyl group. The oxidative rearrangement products, however, are mainly formed when the substituents are methyl or ethyl group on the carbon atoms. It is interesting to see that the sigmatropic rearrangement of 2-ethyl aziridine gave only cis olefinic compound selectively in case that t-butyl group was substituted on the nitrogen, whereas N-hydroxy aziridine compounds were formed exclusively when t-butyl group was replaced with ethyl group.

• YAKHAK HOEJI
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• v.48 no.1
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• pp.88-92
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• 2004

In this study; a series of 2',4'-doubly branched carbocyclic nucleosides (8,9,10) were synthesized from simple acyclic ketone derivative as starting material. The installation of the 4'-quaternary carbon needed was carried out using a 〔3,3〕-sigmatropic rearrangement. In addition, the introduction of a methyl group in the 2'-position was accomplished by Grig-nard reaction. Bis-vinyl was successfully cyclized using a Grubbs' catalyst II. The natural bases (adenine, cytosine, uracil) were efficiently coupled with the use of a Pd(0) catalyst. Although all the synthesized compounds were assayed against several viruses, only cytosine analogue 9 showed weak antiviral viral activity (EC$_{50}$=45.4 $\mu$M) against CoxB3 virus.s.

• YAKHAK HOEJI
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• v.50 no.2
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• pp.65-69
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• 2006

Novel 4'-hydroxymethyl branched thioapiosyl nucleosides were synthesized in this study. The introduction of hydroxymethyl group in the 4'-position was accomplished by a [3,3]-sigmatropic rearrangement. Thioapiosyl sugar moiety was constructed by sequential ozonolysis, reduction and cyclization. The pyrimidine nucleosidic bases (uracil, 5-fluorouracil, 5-iodouracil, 5-chlorouracil, 5-bromouracil) were efficiently coupled by Vorbruggen glycosyl condensation procedure (per-silyated base and TMSOTf). The antiviral activities of the synthesised compounds were evaluated against the HIV-1, HSV-1, HSV-2 and EMCV 5-Iodouracil 18 showed weak antiviral activity against HSV-1 $(EC_{50}=30.7{\mu}M)$.

• YAKHAK HOEJI
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• v.49 no.1
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• pp.20-24
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• 2005

The synthesis of 4',5'-doubly branched carbocyclic nucleosides was accomplished in this study. The selective methylation in the 5'-position was made by Felkin-Anh controlled Grignard addition. The construction of the required 4'-quaternary carbon was carried out by using a [3,3]-sigmatropic rearrangement. Bis-vinyl 6 was successfully cyclized using a Grubbs' catalyst II. The natural pyrimidine bases (cytosine, uracil, thymine) were efficiently coupled using a Pd(0) catalyst. When the synthesized compounds were examined for their activity against several viruses such as the HIV-1, HSV-1, HSV-2 and HCMV, the cytosine analogue 13 exhibited weak antiviral activity against the HCMV.

• Journal of the Korean Society of Safety
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• v.11 no.4
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• pp.84-89
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• 1996

The Oxidation of aflatoxin $G_1$ ($AFG_1$) with ozone in chloroform solvent gave the stable ozonide into ozonization of the double bond in the terminal furan ring, and this reaction have been carried out for 3hr at -78. 5$^{\circ}C$. The chloroform solvent was removed in a stream of nitrogen and the residue was separated by elution chromatography(EC). The structure of this compound have been identified by using MS, $^1H-NMR$, $^l3C-NMR$ and I. R spectroscopy, respectively. This compound was formed the normal stable AFG$_1$-ozonide into spontaneous rearrangement after unstable ozonide according to sigmatropic rearrange ment dependent upon cyclo addition by ozone.