• Bulletin of the Korean Chemical Society
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• v.28 no.9
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• pp.1545-1548
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• 2007

This paper discusses the racemic and stereoselective synthetic route for novel 4'α -methyl and 6'α -methyl analogues of abacavir. The quaternary carbon at the 4'-position of carbocyclic nucleoside was installed successfully via a Claisen rearrangement. The stereocontrolled construction of a methyl group in the 6'α - position was directed through the Felkin-Anh rule. A Bis-vinyl compound 9 was cyclized successfully using Grubbs' catalyst II to provide a carbocycle nucleus for the target compound. The synthesized compound 15 showed moderate anti-HIV activity (EC50 = 10.67 μM, MT-4 cell lines).

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.750-751
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• 2006

We investigated the mechanism how the high green density can be provided during die lubricated warm compaction (WD). We observed and analyzed the densification processes of iron powders including different contents of an inner lubricant, and measured the lateral pressure at the die wall during WD in comparison with conventional compaction and warm compaction. As a result, the high density in WD was due to not only the particles-deformation enhanced by warming powders but also the particles-rearrangement promoted by reducing an amount of the inner lubricant rather than the die lubrication.

• Archives of Pharmacal Research
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• v.28 no.2
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• pp.129-141
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• 2005

(-)-Fumagillol (1), a hydrolysis product of fumagillin, has been synthesized by several group from commercially available 1,2:5,6-di-O-isopropylidene-${\alpha}$-D-allofuranose in a highly stereoselective manner. Chiral centers on C5 and C6 came from D-allofuranose and the asymmetric center on C4 was accomplished by 1,3-chirality transfer using the Claisen rearrangement on a chiral allyl alcohol. Chirality, which is necessary on an epoxide consisting of the spiro-ring system, was diastereoselectively constructed by the well-known reaction, intramolecular ester enolate alkylation (IEEA), which showed that this reaction can be applied to the alpha-alkoxy ester system. The epoxide on the side chain was regioselectively introduced by the difference between the number of substituents on the vinyl groups. This accomplishment proved that IEEA can be a useful tool for the synthesis of complex molecules.

• Bulletin of the Korean Chemical Society
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• v.32 no.3
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• pp.909-914
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• 2011

An improved convergent and economical method has been developed for the synthesis of erlotinib, a 4-anilinoquinazoline and an EGFR-tyrosine kinase inhibitor for treatment of non-small-cell lung cancer. The final two steps for the formation of this 4-anilinoquinazoline from suitable 2-aminobenzonitrile intermediate and 3-ethynylaniline were modified and were performed in a simple one-pot reaction. The ring-closing mechanism for the formation of erlotinib from the suitable formamidine intermediate and 3-ethynylaniline was investigated and determined to proceed via the formation of phenyl benzamidine intermediate rather than involving Dimroth rearrangement reported earlier. The new benzamidine intermediate was isolated for the first time and characterized.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.65-70
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• 2011

Coumarins are ubiquitous in plant kingdom and have been used as antitumor, antifungals, anticoagulants, insecticides. Chalcones are also widespread in plant kingdom and have been known to possess diverse biological activities; antibacterial, antifungal, antitumor and anti-inflammatory, etc. As they are considered as important natural products, numerous synthetic approaches have been reported up to the present. We devise a new selective method of preparing dihydrocoumarins and chalcones from aryl cinnamates by the selection of reagents. Dihydrocoumarin derivatives were prepared selectively by using intramolecular cyclization catalyzed by p-toluene sulfonic acid. Also, chalcones were prepared by Fries-rearrangement catalyzed by $TiCl_4$. This method can be used for preparing various coumarin & chalcone compounds.

• Bulletin of the Korean Chemical Society
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• v.31 no.10
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• pp.2783-2785
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• 2010

Searching for new molecular radicals which are believed to play an important role as reaction intermediates in aromatic chain reactions, we have applied the technique of corona excited supersonic expansion employing a pinhole-type glass nozzle to obtain the vibronic spectrum from the corona discharge of precursor 3,5-difluorotoluene with a large amount of inert carrier gas helium. An analysis of the observed spectrum revealed that many vibronic bands are from other isomeric difluorobenzyl radicals generated in the jet by migration of the fluorine atom or methylene group to the adjacent position in the 3,5-difluorobenzyl radical. A possible mechanism was proposed for the formation of other isomers by using a bridged cyclic intermediate structure.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1812-1816
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• 2004

The stereoselective synthesis 4′,6′-dually branched carbocyclic nucleosides was accomplished in this study. The introduction of a methyl group in the 6′$({\alpha})$-position was accomplished by Felkin-Anh controlled alkylation. The construction of the required 4′$({\alpha})$-quaternary carbon was carried out using a [3,3]-sigmatropic rearrangement. Bis-vinyl 6 was successfully cyclized using a Grubbs' catalyst II. The natural bases (adenine, cytosine) 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 good antiviral activity against the HCMV.

• Bulletin of the Korean Chemical Society
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• v.30 no.12
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• pp.2959-2961
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• 2009

Total synthesis of (${\pm}$)-licochalcone E (1), an allyl retrochalcone isolated from roots of Glycyrrhiza inflata, has been achieved from 4-tetrahydropyranyloxyacetophenone (7) with (E)-2-methoxy-4-(2-methyl-2-butenyloxy)benzaldehyde (6) or (Z)-2-methoxy-4-(2-methyl-2-butenyloxy)-benzaldehyde (11) through a convergent strategy involving aldol condensation and Claisen rearrangement as key steps.

• Bulletin of the Korean Chemical Society
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• v.29 no.9
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• pp.1723-1728
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• 2008

An efficient synthetic route for carbocyclic versions of stavudine analogues and their evaluation on antiviral activity are described. The construction of an ethynylated quaternary carbon at the 4'-position of carbocyclic nucleosides was accomplished using Claisen rearrangement of 11 and ring-closing metathesis (RCM) of dienyne 14 as key transformations. An antiviral evaluation of the synthesized compounds, 20, 21, 22, and 25 against HIV-1, HSV-1, HSV-2, and HCMV showed that only the guanine analogue 25 is moderately active against HIV-1 in the MT-4 cell line ($EC_{50}$ = 11.91 $\mu$mol).

• Archives of Pharmacal Research
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• v.27 no.2
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• pp.136-142
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• 2004

In this study, a highly diastereoselective synthesis of anti-1 ,2-aminoalcohol was explored starting from L-amino acids as chiral sources. The higher yield and diastereoselectivity was shown when the aza-Claisen rearranqement was performed with allylic trichloroacetimidate 6a in the presence of palldium(II) catalyst.