Tyrosine enantioseparation

Fig. 21 LC and SFC enantioseparations of propranolol on a derivatized tyrosine Pi ride CSP. Mobile-phase conditions LC, 95 5 hexane/(ethanol containing 1% n-propylamine) (v/v) SFC, 90/10 carbon dioxide/(methanol containing 1% n-propylamine) (v/v) [179]. Molecular modeling results are presented for (a) optimized structure of (/J)-propranolol without CO2 and (b) optimized stiucture of (/J)-propranolol with CO2. The intramolecular hydrogen bonding is denoted by an arrow (adapted from [183])...

Elek et al. evaluated different dual selector systems containing a CD derivative (Me-(3-CD and DM-(3-CD) and a new diazacrown ether derivative (A-[2-(l,4,10,13-tet-raoxa-7,16-diazacyclooctadecan-7-yl)propanoyl]glycine) (RS-1) for the enantioseparation of Trp-methylester (Trp-ME) and tyrosine-methylester (Tyr-ME) enantiomers. For this separation, a 56.5-cm-long (50.00 cm effective length), 75- JLm i.d. uncoated fused-silica capillary was used. Trp-ME was baseline separated (Rs= 1.93) when a 44.7-mM phosphate buffer with pH 2.27, containing 28.6-mM DM-(3-CD and 47-mM diazacrown-ether derivative, was applied. The best separation for Tyr-ME (Rs = 1.05) was... 

The first cellulose enantioseparation was of a racemic amino acid by paper chromatography [8]. Early cellulose TLC smdies were aimed at repeating paper chromatography enantiomer separations more quickly and with better resolution. Cellulose TLC has mostly been used for amino acids, their derivatives, and peptides and the following are examples of successful enantioseparations. Aromatic amino acids were separated on polyester-backed 20 x 20 cm plates by elution with methanolic aqueous 0.1 M HCl (A) or ethanol/pyridine/water (1 1 1) (B). Typical respective R values were 0.75/0.81 for l- and o-tyrosine in mobile phase A and 0.37/0.46 for L- and D-5-methyl tryptophan in B [9,10]. 

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