A practical method to access enantiopure β-perfluoroalkyl-β-amino acids: diastereoselective reduction of cyclic enamino-esters
摘要:
A highly practical method to access enantiopure beta-perfluoroalkyl-beta-amino acids was developed, which Could be conducted Without any expensive reagent, special apparatus/technique, nor tedious chromatographic separation. The condensation of methyl 4,4,4-trifluoro-3-oxobutanoate with (S)-2-amino-2-phenylethanol, followed by an intramoleculer transesterification, gave an enamino-ester with a seven-membered ring structure. The hydride reduction of the cyclic enamino-ester proceeded with excellent diastereoselectivity (dr = 95:5-97:3) to give the corresponding cyclic amino-ester. The major isomer of the cyclic amino-ester was readily separated from the minor one and successfully converted into (S)-3-amino-4,4,4-trifluorobutanoic acid (five steps, 38% overall yield, >99% ee). Concerning the key step of this synthesis, the same strategy was applicable to another substrate: the asymmetric hydride reduction of a cyclic enamino-ester with a pentafluoroethyl group also proceeded in excellent diastereoselectivity (dr = 96:4). (C) 2009 Elsevier Ltd. All rights reserved.
Synthesis and evaluation of chiral β-amino acid-based low-molecular-weight organogelators possessing a methyl/trifluoromethyl side chain
作者:Koichi Kodama、Ryuta Kawamata、Takuji Hirose
DOI:10.1039/c8nj05668d
日期:——
The synthesis and gelation properties of chiral β-amino acid-based low-molecular-weight organogelators, possessing methyl/trifluoromethyl sidechains, are reported. The structure of the sidechain and chirality were found to be important parameters affecting the gelation ability. The pure enantiomer of the trifluoromethylated β-amino acid displayed good gelation properties due to the formation of fibrillar
A highly practical method to access enantiopure beta-perfluoroalkyl-beta-amino acids was developed, which Could be conducted Without any expensive reagent, special apparatus/technique, nor tedious chromatographic separation. The condensation of methyl 4,4,4-trifluoro-3-oxobutanoate with (S)-2-amino-2-phenylethanol, followed by an intramoleculer transesterification, gave an enamino-ester with a seven-membered ring structure. The hydride reduction of the cyclic enamino-ester proceeded with excellent diastereoselectivity (dr = 95:5-97:3) to give the corresponding cyclic amino-ester. The major isomer of the cyclic amino-ester was readily separated from the minor one and successfully converted into (S)-3-amino-4,4,4-trifluorobutanoic acid (five steps, 38% overall yield, >99% ee). Concerning the key step of this synthesis, the same strategy was applicable to another substrate: the asymmetric hydride reduction of a cyclic enamino-ester with a pentafluoroethyl group also proceeded in excellent diastereoselectivity (dr = 96:4). (C) 2009 Elsevier Ltd. All rights reserved.