• Journal of the Korean Chemical Society
• /
• v.55 no.2
• /
• pp.251-255
• /
• 2011

A new and highly stereoselective synthesis of (E)-4'-amino-3,4,5-trimethoxystilbene was achieved by using 3,4,5-trimethoxybenzaldehyde and p-nitrotoluene as starting materials through condensation under solvent-free condition and followed by the reducing of nitro group with the system of $NH_2NH_2/FeCl_3$/C in ethanol. The crystal structure of (E)-4'-amino-3,4,5-trimethoxystilbene was also determined by X-ray diffraction analysis.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.1
• /
• pp.163-171
• /
• 2009

Few $\alpha$-Hydroxy-$\beta$-amino acids were synthesized via various nucleophilic addition of the epoxide and followed by stereoselective nucleophilic substitution reaction and eliminative cleavage of the acetal selectively in diacetal compound. One of the synthesized $\alpha$-Hydroxy-$\beta$-amino acid reacted with L-leucine methylester to give corresponding dipeptide in good yields.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.10
• /
• pp.1520-1524
• /
• 2005

This paper describes the racemic and stereoselective synthetic route for a novel 4'$\alpha$-phenyl and 6'$\alpha$-methyl doubly branched carbocyclic nucleosides from an acyclic 2-hydroxy acetophenone. The installation of phenyl group at the 4'-position of carbocyclic nucleoside was successfully accomplished via a sequential [3,3]-sigmatropic rearrangement. The stereoselective introduction of a methyl group in the 6'$\alpha$-position was accomplished by Felkin-Anh controlled alkylation. Bis-vinyl 11 compound was successfully cyclized using a Grubbs’ catalyst II to desired carbocycles. The natural bases (adenine and cytosine) were efficiently coupled using a Pd(0) catalyst. Although all the synthesized compounds were examined for their activity against several viruses such as HIV-1, HSV-1, HSV-2 and HCMV, only cytosine analogues 17 exhibited weak antiviral activity against HCMV.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.7
• /
• pp.625-630
• /
• 1995

α-Linked D-altropyranosidic derivatives were obtained by configurational change at C-3 of α-D-mannopyranosides as the key step in preparation of allyl and methyl α-D-glycopyranosides of 6-deoxy-D-altro-heptose. The manno-altro conversion was effected by sequential reactions of Swern oxidation and stereoselective borohydride reduction. Allyl 4,6-O-benzylidene-2-O-p-methoxybenzyl-α-D-mannopyranoside was transformed to the corresponding altropyranoside via 3-oxo-arabino-hexopyranoside. Allyl 7-O-benzyl-6-deoxy-3,4-O-isopropylidene-α-D-altro-heptopyranoside has been prepared as a glycosyl acceptor to be coupled with β-D-GlcpNAc-(1→3)-α-D-Galp glycosyl donor for the synthesis of an O-antigen repeating unit of Campylobacter jejuni serotypes O:23 and O:36. Stereoselective borohydride reduction also succeeded in yielding methyl 2,4,7-tri-O-benzyl-6-deoxy-α-D-altro-heptopyranoside from the corresponding 3-oxo-α-D-arabino-heptopyranoside. C-6 Homologation was achieved by sequential reactions of cyanide displacement of 6-sulphonates, reduction of the resulting heptopyranosidurononitrile with diisobutylaluminum hydride, hydrolysis of the imine, and further reduction with sodium borohydride.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.11
• /
• pp.3554-3558
• /
• 2012

A new highly stereoselective synthesis of pyrrolidine azasugar 1,4-dideoxy-1,4-imino-D-galacitol is being reported herein. The synthesis was achieved in a linear sequence and inexpensive chiral source (+)-diethyl tartarate was used as the starting material. The key step involved during the synthesis was Pd catalysed amino cyclization of alkenylamine, Bose modified Mitsunobu reaction and Sharpless asymmetric dihydroxylation.

• Applied Chemistry for Engineering
• /
• v.25 no.4
• /
• pp.392-395
• /
• 2014

(2S,3S,4S)-3,4-Dihydroxyglutamic acid (DHGA), a biologically active ${\alpha},{\beta}$-dihydroxy-${\gamma}$-amino acid, was efficiently synthesized from a readily available D-serine derivative in 30% overall yield over 11 steps. The key stereoselective $OsO_4$-catalyzed dihydroxylation reaction controlled by an N-diphenylmethylene group on the amino group of ${\gamma}$-amino-${\alpha},{\beta}$-unsaturated (Z)-ester successfully introduced the diol moiety of the intermediate 5a in 86% with more than 10 : 1 diastereomeric ration. Then it was in turn successfully converted to the desired target compound, (2S,3S,4S)-3,4-DHGA, via simple oxidation and hydrolysis in a highly stereoselective manner and a higher yield than the previous syntheses. This result strongly supports that our synthetic methodology of stereoselective $OsO_4$-catalyzed dihydroxylation should be useful in stereoselctive synthesis of various bioactive compounds with an amino diol moiety.

• Journal of the Korean Chemical Society
• /
• v.36 no.4
• /
• pp.579-583
• /
• 1992

Stereoselective synthesis of farnesol, (2E, 6E)-3,7,11-trimethyldodeca-2,6,10-tiren-1-ol(1), was carried out using 5-bromo-2-methylpent-2-ene(2) as a starting material. After conversion of 5-bromo-2-methylpent-2-ene(2) to the corresponding iodide compound, 5-(4-methylpent-3-enyl)-2,3-dihydrofuran(4) was obtained by alkylation of 5-lithio-2,3-dihydrofuran with 5-iodo-2-methylpent-2-ene. Ni(0)-catalyzed coupling reaction of the dihydrofuran 4 with MeMgI was proceeded to give (3E)-4,8-dimethylnona-3,7-dien-1-ol(5) in 72% yield. The resultant homoallylic alcohol 5 was converted to the (5E)-6,10-dimethylundeca-5,9-dien-2-one(8) in 4 steps. Compound 8 was condensed with dimethylmethoxycarbonylmethylphosponate in benzene follwed by $NaBH_4$ reduction in EtOH to yield (2E, 6E)-3,7,11-trimethyldodeca-2,6,10-trien-1-ol(1). Ni(0)-catalyzed coupling reaction of MeMgI with dihydrofuran 4 was a key step in this synthesis of farnesol(1).

• Bulletin of the Korean Chemical Society
• /
• v.23 no.1
• /
• pp.86-92
• /
• 2002

A short synthesis of novel prostanoids, 12-epi-carbacyclins 3 and 24, has been accomplished using palladium chemistry as a key step. The silyl enol ether 10a prepared through organopalladium chemistry has been allowed to react with 1-octen-3-one in the presence of $Pd(OAc)_2$ to give compound 12 in a single step. The unusual chemo- and stereoselective reduction of the ${\alpha},{\beta}$-unsaturated ketone in 12 has been effected with (S)-BINALH. Subsequent desilylation and Wittig reaction have provided the Subsequent desilylation and Wittig reaction have provided the $PGI_2$ analogues 3 and 24.

• Journal of the Korean Chemical Society
• /
• v.57 no.5
• /
• pp.591-598
• /
• 2013

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.3
• /
• pp.570-576
• /
• 2010

A variety of ynamides undergo highly regio- and stereoselective radical addition of arenethiols with the aid of triethylborane as a radical initiator. The products, N-[(Z)-2-arylsulfanyl-1-alkenyl]amides, can be reduced with triethylsilane in trifluoroacetic acid to yield N-[2-(arylsulfanyl)alkyl]amides.