Joong-Gon Kim

A mild and efficient procedure for the preparation of acid chlorides from car☐ylic acids

Abstract Various car☐ylic acids are converted into the corresponding acid chlorides by treatment with trichloroacetonitrile and triphenylphosphine in methylene chloride at room temperature. Aryl acids show higher reactivity than alkyl acids under the conditions.

Trifunctional methacrylate monomers and their photocured composites with reduced curing shrinkage, water sorption, and water solubility.

Novel trifunctional methacrylates, 1,1,1-tris[4-(2-acetoxy-3-methacryloyloxypropoxy)phenyl]ethane (Ac-THMPE) and 1,1,1-tris[4-(2-acetoxy-3-methacryloyloxypropoxy)phenyl]methane (Ac-THMPM), have been prepared by acetylation of the hydrophilic hydroxyl groups of 1,1,1-tris[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]ethane (THMPE) and 1,1,1-tris[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]methane (THMPM), respectively, for use as dental monomers. Decrease in monomer viscosity resulted from the acetylation. Unfilled resins and composites based on the four trimethacrylates were evaluated for photopolymerization conversion, water contact angle, and curing shrinkage. Water sorption, water solubility, and flexural strength of the composites prepared from the trimethacrylate were measured. Those data obtained for the trimethacrylate-containing materials were compared with control 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (bis-GMA)-based materials in order to evaluate the applicability of the trimethacrylates as dental monomers. The acetylation of hydroxyl groups appeared to be an effective method to decrease curing shrinkage, water sorption, and water solubility of the dental composites. When compared with the bis-GMA composite, the composites based on Ac-THMPM and Ac-THMPM showed much lower curing shrinkage, water sorption, and water solubility, along with approximately equal conversion and flexural strength.

Intramolecular cyclopropanation using iodonium ylides. The 3,5-cyclovitamin D ring A synthon

Abstract The key intermediate 2b for 3,5-cyclovitamin D ring A synthon 13 was prepared in 80% yield as a diastereomeric mixture (70:30) via intramolecular cyclopropanation from iodonium ylide 10b.

A CONVENIENT METHOD FOR SYNTHESIS OF SYMMETRICAL ACID ANHYDRIDES FROM CARBOXYLIC ACIDS WITH TRICHLOROACETONITRILE AND TRIPHENYLPHOSPHINE

Various carboxylic acids are converted into the corresponding carboxylic acid anhydrides treated with trichloroacetonitrile and triphenylphosphine in the presence of triethylamine at room temperature.

Agrostistachin, a novel cytotoxic macrocyclic diterpene from

Abstract Agrostistachin, a cytotoxic constituent of Agrostistachys hookeri , was characterized as a new member of the rare casbane class of diterpenoids. The structure and stereochemistry of this compound were established by analysis of its spectral and X-ray crystallographic parameters.

Radical deoxygenation of alcohols via their trifluoroacetate derivatives with diphenylsilane

Abstract Trifluoroacetate derivatives of alcohols can be used as precursors for the radical deoxygenation of alcohols with diphenylsilane. The reaction afforded high isolated yields of the deoxygenated products and neutral reaction conditions.

A general synthetic route to A-ring hydroxylated vitamin D analogs from pentoses

Abstract The enyne needed for coupling to a CD-ring fragment, namely, 3 S , 5 R -oct-1-en-7-yne-3,5-diol, in the Trost-Dumas carbopalladation route to 1α, 25-dihydroxyvitamin D 3 was synthesized from D -xylose in 13 steps and 21% yield.

One-Pot Preparation of Esters from Carboxylic Acids Using the PPh3-CCl3CN System

Abstract A convenient one-pot process for preparing various esters from carboxylic acids using the Ph3P-CCl3CN has been developed. Racemic α-tocopherol, clofibrate and flavoxate were prepared in high yields using this method.

A convenient synthesis of 1α,25-dihydroxy-28-norvitamin D2

Abstract The title compound was synthesized via the Julia olefination using ring B-diene protected 3β-hydroxy-23,24-bisnorchola-5,7-diene-22-al acetate and the side-chain synthon 2-methyl-4-phenylsulfonyl-2-(tetrahydropyranyloxy)butane. Ring B-deprotection, photolysis, Paaren-DeLuca hydroxylation and separation of the 5,6 E and Z stereoisomers completed the synthesis in overall 3% yield.

In vivo molecular imaging of [125I]-labeled 3-iodothyronamine: a hibernation-inducing agent.

The present investigation was carried out with the objective of studying in vivo imaging of 3-iodothyronamine (T(1)AM) compound in mice. A simple and efficient synthesis of [(125)I]-T(1)AM was established, and a molecular imaging study was performed using micro-SPECT/CT at 1h post-injection of [(125)I]-T(1)AM. Imaging studies revealed the activity in the gastrointestinal tract and liver, indicating that [(125)I]-T(1)AM was distributed primarily in the liver, and excreted into the gastrointestinal tract through a bile duct.