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Asymmetric Synthesis via Heterocyclic intermediates, L. – Trichloroacetimidates, II. Asymmetric Synthesis of α‐Amino Acid Benzyl Esters via the Bisbenzyl Bislactim Ether of cyclo(‐ L ‐Val‐Gly‐)
Author(s) -
Groth Ulrich,
Schmeck Carsten,
Schöllkopf Ulrich
Publication year - 1993
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199319930153
Subject(s) - chemistry , alkylation , trifluoroacetic acid , ether , benzyl bromide , hydrolysis , bromide , enantiomer , aqueous solution , organic chemistry , medicinal chemistry , stereochemistry , catalysis
The diketopiperazine cyclo(‐ L ‐Val‐Gly‐) ( 1 ) can be O ‐alkylated under mild acidic reaction conditions with the alkyl trichloroacetimidates 2 to the corresponding bisalkyl bislactim ethers. Alkylation of the bisbenzyl bislactim ether anion of cyclo(‐ L ‐Val‐Gly‐) 4c with benzyl bromide and subsequent hydrolysis with aqueous trifluoroacetic acid afforded D ‐phenylalanine benzyl ester ( 8 ) with an enantiomeric excess of > 95%.