• YAKHAK HOEJI
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• v.43 no.1
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• pp.11-15
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• 1999

A brief route for regiospecific synthesis of novel 10-Oxodaunomycinone Derivatives (10a, b) is described. Dimethoxy-l-tetralone 4 was converted to acetyl tetralone (5a, b) which was oxidized with oxygen to obtain cis-diol compound (8a, b). The construction of (10a, b) was completed by the condensation of phthaloyl dichloride 9 with cis-diol (8a, b)

• Bulletin of the Korean Chemical Society
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• v.30 no.9
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• pp.2039-2042
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• 2009

As a part of an ongoing effort to discover inhibitors of the Hepatitis C Virus RNA replication, we describe here the first synthetic route of 1'($\alpha$),2'($\beta$)-C-dimethyl carbocyclic adenine analogue. The key intermediate cyclopentenyl alcohol 8($\alpha$) was prepared from aldehyde 4 using ring-closing metathesis (RCM) as a key reaction. Coupling of 8($\alpha$) with nucleosidic base via the regioselective Mitsunobu reaction followed by stereoselective dihydoxylation and deprotection afforded the target carbocyclic adenine analogue 12.

• Bulletin of the Korean Chemical Society
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• v.33 no.1
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• pp.76-82
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• 2012

A novel and efficient tetrahydrofuranyl ring opening method was developed using the highly reactive TFAT reagent in the presence of an acid scavenger, 2,6-di-tert-butyl-4-methylpyridine. Various acid sensitive groups are compatible with the reaction condition, making it generally applicable to many tetrahydrofuranyl steroids. Moreover, it is a synthetic equivalent of 'Marker degradation' affording an efficient synthesis of C17-OH rockogenin acetate.

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

• Bulletin of the Korean Chemical Society
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• v.30 no.5
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• pp.1003-1008
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• 2009

The $O_sO_4$-catalyzed dihydroxylations of a monosubstituted allylic amine and $\gamma-amino-\alpha,\;\beta-unsaturated$ (E)-esters with bulky alkyl groups showed a high anti-selectivity. Since the acyclic conformation of N-acyloxy protected allylic amines was efficiently controlled by a bulky t-Bu or OBO ester group, the anti diastereoselectivity of >12.5:1 was obtained without applying a chiral reagent. The synthetic utility of the present method was demonstrated by a stereoselective and efficient synthesis of an $\alpha$-glucosidase inhibitor 15 from commercially available N-Cbz-L-serine 6 in 11 steps and 31% yield.

• Bulletin of the Korean Chemical Society
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• v.30 no.11
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• pp.2626-2630
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• 2009

2'($\beta$)-Hydroxymethylated adenosine is a potent and selective inhibitor of hepatitis C virus (HCV) replication. It targets the RNA-dependent RNA polymerase of HCV, NS5B. Synthesis and antiviral evaluation of carbocyclic versions are described. The cyclopentene intermediate ($9\beta$) was successfully synthesized through sequential Johnson-Claisen orthoester rearrangement and ring-closing metathesis (RCM). Coupling of bases via a Pd(0) catalyst, selective dihydroxylation, and desilylation yielded the target nucleoside analogues. The compounds 17 and 18 were assayed for their ability to inhibit HCV RNA replication in a subgenomic replicon Huh7 cell line and showed moderate antiviral activity with toxicity up to 20.0 and 24.7 ${\mu}g/mL$, respectively.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1059-1063
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• 1998

Regiospecific total syntheses of (±)-11-deoxy-4-methoxy-10-oxo-βrhodomycinone (21a) and (±)-11-deoxy-1-methoxy-10-oxo-β-rbodomycinone (21b) are described. 2-(2-Bromoethyl)-1,3-dioxane (6) was transformed to naphthalenone 12, which was condensed with (phenylsulfonyl)-isobenzofuranone 13 to afford 7,8-dihydro-9-ethyl-6-hydroxy-4-methoxynaphthacen-5,12-dione (15). Epoxide 16 prepared from olefinic compound 15, reacted with HF/Pyr (7:3) to give 17. Dihydroxylation of 17 with t-BuOK/P(OMe)3/O2, selective cis-diol protection of mixed compounds 18 with phenylboronic acid in toluene, separation of cis-boronate 19 and trans-diol 20 by column chromatography on silica gel, and cleavage of the boronate group of 19 with 2-methylpentane-2,4-diol in acetic acid completed the construction of 21.

• Journal of the Mineralogical Society of Korea
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• v.32 no.3
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• pp.201-211
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• 2019

The particle size and crystallinity of fault gouge generally decreases with slip. Phyllosilicates including talc are known to be present in fault gouge and play an important role in fault weakening. In particular, the coefficient of friction varies depending on the presence of a water molecule on the surface of mineral. The purpose of this study is to investigate the effect of talc on fault weakening by changing the water content and dehydration behavior of talc before and after grinding, which systematically varied particle size and crystallinity using high energy ball mill. Infrared spectroscopy and thermal analysis show that the as-received talc is hydrophobic before grinding and the water molecule is rarely present. After grinding up to 720 minutes, the particle size decreased to around 100 ~300 nm, and in talc, where amorphization proceeded, the water content increased by about 8 wt.% and water molecule would be attached on the surface of talc. As a result, the amount of vaporized water by heating increased after grinding. The dihydroxylation temperature also decreased by ${\sim}750^{\circ}C$ after 720 minutes of grinding at ${\sim}950^{\circ}C$ before grinding due to the decrease of particle size and crystallinity. These results indicate that the hydrophobicity of talc is changed to hydrophilic by grinding, and water molecules attached on the surface, which is thought to lower the coefficient of friction of phyllosilicates. The repeated slip throughout the seismic cycle would consistently lower the coefficient of friction of talc present in fault gouge, which could provide the clue to the weakening of matured fault.