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Enantioselektive α‐Alkylierung von Asparagin‐ und Glutaminsäure über die Dilithium‐enolatocarboxylate von 2‐[3‐Benzoyl‐2‐( tert ‐butyl)‐1‐methyl‐5‐oxoimidazolidin‐4‐yl]essigsäure und 3‐[3‐Benzoyl‐2‐( tert ‐butyl)‐1‐methyl‐5‐oxoimidazolidin‐4‐yl]propionsäure
Author(s) -
Aebi Johannes D.,
Seebach Dieter
Publication year - 1985
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19850680603
Subject(s) - chemistry , dilithium , benzoyl chloride , alkylation , acetic acid , electrophile , hydrolysis , enantioselective synthesis , glutamic acid , deprotonation , medicinal chemistry , organic chemistry , amino acid , catalysis , ion , biochemistry
Overall Enantioselective α‐Alkylation of Aspartic and Glutamic Acid through Dilithium Enolatocarboxylates of 2‐ [3‐Benzoyl‐2‐( tert ‐butyl)‐1‐methyl‐5‐oxoimidazolidin‐4‐yl]acetic and 3‐[3‐Benzoyl‐2‐( tert ‐butyl)‐1‐methyl‐5‐oxoimidazolidin‐4‐yl]propionic Acid, respectively The pure methyl esters 10 of the heterocyclic carboxylic acids specified in the title were prepared in several steps by known methods from aspartic and glutamic acid, with overall yields of ca. 20%. The corresponding heterocyclic acids 11 were doubly deprotonated by LiNEt 2 /BuLi or LiN(i‐Pr) 2 /BuLi to give enolatocarboxylates ( 3 ). The latter were reacted with electrophiles (MeOD, Mel, C 6 H 5 CH 2 Br) to give the crystalline products 14 – 21 diastereoselectively. Hydrolysis of the imidazolidinone ring of three such products gave the corresponding α‐branched aspartic and glutamic acids 22 – 24 of known absolute configuration, thus establishing the stereochemical course of the overall enantioselective alkylations.