Byeong-Seon Jeong

Trimeric Cinchona alkaloid phase-transfer catalyst: α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide

A trimeric Cinchona alkaloid ammonium salt, α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide has been prepared as a novel phase-transfer catalyst. The catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using the trimer catalyst showed high enantioselectivity (90–97% ee).

Highly efficient ortho-fluoro-dimeric cinchona-derived phase-transfer catalysts

A series of cinchona alkaloid-derived dimeric quaternary ammonium salts were prepared as chiral phase-transfer catalysts by the introduction of various functional groups on the phenyl ligand. Among them, the 2-F-substituted derivative 21 showed the highest enantioselectivity in the alkylation of the glycine anion equivalent 1 (97 to >99% ee).

Structure-activity relationship study of asiatic acid derivatives for new wound healing agent.

Ten semi-synthetic derivatives of asiatic acid were prepared and their wound healing effects were evaluated by employing a tensile strength assay and a wound area assay. Among them, ethoxymethyl 2-oxo-3,23-isopropylidene-asiatate (12) showed the strongest and the fastest wound healing activity. Furthermore, it left the smallest scar after healing.

Synthesis and application of dimeric Cinchonaalkaloid phase-transfer catalysts:α,α′-bis[O(9)-allylcinchonidinium]-o,m, or p-xylene dibromide

A dimeric Cinchona alkaloid ammonium salt, α,α′-bis[O(9)-allylcinchonidinium]-m-x ylene dibromide 4, has been developed as a new efficient phase-transfer catalyst; the catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using 4 provided 7 in a high enantiomeric excess (90–99% ee).

Asymmetric synthesis of (S)-4-(2,2,4-trimethyl-1,3-dioxolan-4-yl)-1-butanol, a key intermediate for (1S,5R)-(−)-frontalin via asymmetric bromolactonization

Abstract A asymmetric synthesis of ( S )-4-(2,2,4-trimethyl-1,3-dioxolan-4-yl)-1-butanol, a key intermediate for (1 S ,5 R )-(−)-frontalin, via asymmetric bromolactonization employing ( S )-(−)-proline as a chiral auxiliary is described.

Asymmetric synthesis of (R)-(+)-etomoxir

Abstract An asymmetric synthesis of etomoxir 1 , involving bromolactonization by using ( S )-(−)-proline as a chiral auxiliary, is reported.

Asymmetric synthesis of (R)-(+)-etomoxir via enzymatic resolution

Abstract An asymmetric synthesis of ( R )-(+)-etomoxir 3 , employing enzymatic resolution of ethyl 2-alkyl-2,3-dihydroxypropionate using Amano AK via transacylation is reported.

Asymmetric synthesis of (S)-α-substituted β-bromo-α-hydroxy acids

Publisher Summary (S)-α-substituted β-bromo-α-hydroxy acids (S)-4 are very important chiral synthon for medicinally important compounds, such as potential new hypoglycemia active alkylglycidic acids and anti-ulcer active misoprost. Herein the chapter shows a new and simple synthetic method for (S)-4 using asymmetric bromolactonization that has been the most dependable method for the chiral α-α-disubstituted α-hydroxy acids.