Soon-Ai Kim

Asymmetric Total Synthesis of Fluvirucinine A1

Diastereoselective vinyl addition to an amide carbonyl group and amide enolate induced aza-Claisen rearrangement are the key steps in the first asymmetric total synthesis of fluvirucinine A(1) (1), the aglycon of fluvirucin A(1). Fluvirucins are a class of macrolactam antibiotics produced by actinomycete strains that show promising biological properties.

A New Ring Expansion Reaction of 1-Acyl-2-vinylpiperidine and 1-Acyl-2-Vinylpiperazine via Aza-Claisen Rearrangement of Amide Enolate

Abstract A new ring expansion reaction of 1-acyl-2-vinylpiperidines and 1-acyl -2-vinylpiperazines has been achieved. Amide enolate induced aza-Claisen rearrangements of 1-acyl-2-azacycles provide the corresponding lactams possessing various substituents at α-position of carbonyl in good yields.

The highly diastereoselective palladium-catalyzed cyclizations. stereoselective syntheses of cis and trans-disubstituted hydroxycyclopentanes

Abstract A new variant of palladium-catalyzed stereoselective cyclization has been developed. This process provides an excellent 1,2-diastereocontrol of two new stereogenic centers as well as 1,3-asymmetric induction. In addition, desulfonylation of the cyclization product with retention of the initial stereochemistry and conversion of the desulfonylation product to the advanced carbaprostacyclin intermediate is described.

Asymmetrische Totalsynthese von Fluvirucinin A1

Die diastereoselektive Vinyladdition an eine Amid-Carbonylgruppe und die Amidenolat-induzierte Aza-Claisen-Umlagerung sind die Schlusselreaktionen der ersten asymmetrischen Totalsynthese von Fluvirucinin A11, dem Aglycon von Fluvirucin A1. Die von Actinomyceten produzierten Fluvirucine sind Makrolactam-Antibiotika mit interessanten biologischen Eigenschaften.

A formal synthesis of (+)-brefeldin A

Abstract A formal synthesis of (+)-brefeldin A has been achieved via stereoselective construction of hydroxycyclopentane skeleton possessing the requisite hydroxyheptenyl side chain. The highly advanced intermediate 2 has been synthesized from the known Weinreb amide in 19% overall yield of 11 steps.

Fracture evaluation of metallic materials at intermediate strain rates

This paper evaluates existing dynamic hardening models and fracture strains for metallic materials of typical crystalline structures: 4130 steel (BCC); OFHC copper (FCC); and Ti6Al4V (HCP). Uniaxial tensile and fracture tests of the representative materials are carried out at intermediate strain rate. In order to describe the dynamic hardening characteristics, several models are compared for each material and the most applicable model for a specific material has been recommended. The fracture tests at strain rates ranging from 0.001s to 100s are conducted with several types of the pure shear, dog bone and grooved specimens for the strain paths of the pure shear, uniaxial tension and plain strain conditions. The fracture strain and the strain path are measured on the surface of the specimen and the Lou-Huh ductile fracture criterion is implemented to describe the fracture loci with respect to the strain rate.

Palladium-Catalyzed Diastereoselective Cyclization of the Allylic Precursors. A Concise Synthetic Route to 3-Azabicyclo[3.3.0]Octane and Hydroisoindole Skeletons

Abstract A useful variant of palladium-catalyzed 1,2-diastereoselective cyclization of the allylic precursors based on the steric nature of the anion stabilizing groups has been developed. The 1,1,2-trisubstituted cycloalkane products have also been efficiently transformed into the azabicyclic systems.

Synthesis of cis-disubstituted cyclohexane synthesis of cis-1-ethenyl-2-hydroxymethyl-cyclohexane

The efficient synthetic routes to cis-1-ethenyl-2-hydroxymethyl-cyclohexane, an useful synthetic intermediate,have been described. Access to the cis-disubstitutd cyclohexane is gained through the Claisen rearrangment and selective DHP protection of diol respectively.