Premium
Alkylations of Chiral Imidazolidinones Derived from Di‐ and Triglycine and Attempts at Cyclisations to Give Cycloisodityrosines
Author(s) -
Bezencon Olivier,
Seebach Dieter
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619960805
Subject(s) - chemistry , enantiopure drug , electrophile , moiety , hydrolysis , alkylation , allylic rearrangement , medicinal chemistry , stereochemistry , organic chemistry , catalysis , enantioselective synthesis
Di‐ and triglycine derivatives ( 1–5 ) containing a 2‐ tert ‐butyl‐1,3‐imidazolidin‐4‐one moiety were prepared in rac. and enantiopure forms. By deprotonations with LiNR 2 these imidazolidinones were converted to Li, Li 2 , and Li 3 derivatives ( H‐N ) and the latter alkylated, preferably with the more reactive electrophiles (MeI, benzylic and allylic bromides). The diastereoselectivity at the endocyclic (imidazolidinone) position is always very high (>95:5), while it varies with respect to the newly formed stereocentres at the exocyclic positions (2:1 to >95:5). Three dozens of new di‐ and triglycine derivatives were thus prepared and fully characterised. Cyclisation attempts with seven different diaryl ethers ( 23, 29, 32, 35, 39, 44, 45 ), which are potential precursors of cycloisodityrosines, failed. The configurations of the products were assigned by X‐ray structure analysis ( 29, 40, 53 ), NMR analysis, and hydrolysis to the amino acid components, followed by GC analysis.