178897-35-3Relevant articles and documents
Stereoselective synthesis of β-benzyl-α-alkyl-β-amino acids from l-aspartic acid
Seki, Masahiko,Shimizu, Toshiaki,Matsumoto, Kazuo
, p. 1298 - 1304 (2007/10/03)
A stereoselective synthesis of β-benzyl-α-alkyl-β-amino acids 1 and 2 from L-aspartic acid 3 has been developed. Methyl 5-phenyloxazolidin-2-one-4-acetate 4 was prepared from L-aspartic acid 3 through the acylation of benzene or phenyllithium with a-amino carboxyl group of L-aspartic acid skeleton. Alkylation of a dianion of 4 with alkyl halides and subsequent hydrogenation afforded cmfi-disubstituted /J-amino acids Ib and le in high stereoselectivities. Complete reversal of the stereoselection was realized by the alkylation of 4-phenyl-3-feri-butoxycarbonylamino-4-butanolide 6 which was obtained in a single step from 4. The 2,3,4-trisubstituted amino lactone 7 thus obtained was hydrogenated to give a syra-disubstituted β-amino acid 2a. The syn-products 2b, 2c, and 2d were alternatively prepared via aldol condensation of 6 with aromatic or aliphatic aldehydes followed by stereoselective reduction of the double bond with nickel chloride-sodium borohydride.