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Synthesis and NMR configurational analysis of 1,3‐imidazolidin‐4‐ones derived from (−)‐( S )‐phenylethylamine
Author(s) -
GarcíaMartínez Cirilo,
CervantesCuevas Humberto,
EscalanteGarcia Jaime
Publication year - 2003
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.10280
Subject(s) - chemistry , stereocenter , intramolecular force , chemical shift , stereochemistry , hydrogen bond , ring (chemistry) , molecule , organic chemistry , catalysis , enantioselective synthesis
The preparation and NMR study in the solution state of (−)‐( S )‐1‐acetyl‐3‐(phenylethyl)‐1,3‐imidazolidin‐4‐one, (−)‐(2 R ,1′ S )‐ and (+)‐(2 S ,1′ S )‐1‐acetyl‐2‐ tert ‐butyl‐3‐(phenylethyl)‐1,3‐imidazolidin‐4‐one, and (−)‐(2 S ,1′ S )‐ and (+)‐(2 R ,1′ S )‐1‐carboethoxy‐2‐ tert ‐butyl‐3‐(phenylethyl)‐1,3‐imidazolidin‐4‐one are described. The orientations of acetyl, carboethoxy, and phenethyl groups attached to nitrogen atoms N‐1 and N‐2 were deduced from the proton and 13 C chemical shifts. The typical orientation of phenethyl group, which has the hydrogen H‐6 syn and close to the oxygen of carbonyl C‐4, was observed in (−)‐( S )‐1‐acetyl‐3‐(phenylethyl)‐1,3‐imidazolidin‐4‐one but not in the other four compounds; nevertheless, interpretation of chemical shifts based on the ring current effects correlated with the true configuration of the new stereogenic center at C‐2. Four of these imidazolidinones were analyzed by X‐ray diffraction to corroborate the configuration determined by NMR. The structures determined by X‐ray diffraction revealed the existence of intramolecular hydrogen bonds capable to control the conformation of the phenethyl and acyl groups in the solution state. Chirality 15:S74–S81, 2003. © 2003 Wiley‐Liss, Inc.