138062-69-8Relevant articles and documents
Relationships Between the Acidity of the Z and E Isomers of N-Nitroso-N-alkyl-α-amino Acids and Their Conformations
Liberek, Bogdan,Ciarkowsky, Jerzy,Plucinska, Krystyna,Stachowiak, Krystyna
, p. 143 - 147 (1982)
The acidity constants of both Z and E conformational isomers of five N-nitroso-N-alkyl-α-amino acids, ON-N(R1)-CH(R2)-COOH, are determined by the observation of selected pH titrated (1)H NMR signals.For two glycine derivatives (1, R1=CH3, R2=H, ON-Sar; R1=C2H5, R2=H, ON-EtGly) and two alanine derivatives (3, R1=CH3, R2=CH3, ON-MeAla; 4, R1=C2H5, R2=CH3, ON-EtAla) the E ismers appear to be stronger acids than the Z while for the third alanine derivative (5, R1=n-C3H7, R2=CH3, ON-PrAla) the opposite is observed.These results, also inducing anisotropy effects associated with the N-NO group, are discussed in terms of conformations.A 7-membered ring conformation with an -NO...HOOC- intramolecular hydrogen bond is proposed to be statistically important in the Z isomers of 1,2,3 and, to a lesser extent, 4.
