IDENTIFICATION OF THE ELUSIVE AMINO ACID 21 
Sufficient information is here provided to permit the stereochemical correlation of 
each of the fourisomers of y-hydroxyglutamic acid with those of the corresponding y-hy- 
droxyprolines, the configurations of which have been previously established. Such cor- 
relations are represented in Fig. 8. Thus, 1-hydroxyproline (structure I) may be con- 
figurationally correlated with y-hydroxy-1-glutamic acid B (structure IT), whereas 
COOH COOH COOH COOH 
NH = H NH» 
CHo ~ 
. | 
HO HO 
\/ 
CHo 
I BG It para 
CHo CH» 
be a 
COOH COOH 
CH» ~ 
i 
CH. 
Fig. 8. Stereochemical relationship of the stereoisomeric forms of y-hydroxyglutamic acid with the 
corresponding forms of y-hydroxyproline. 
L-allohydroxyproline (structure III) is the stereochemical equivalent of y-hydroxy- 
glutamic acid A (structure IV). The validity of these correlations was recently demon- 
strated by ADAMS AND GOLDSTONE”, who showed that y-hydroxy-.-glutamic acid B 
(structure IT) isa metabolic product, in the mammal, of t-hydroxyproline (structure I). 
With this in mind, it now becomes possible to eliminate the A and B designations for 
the diastereomeric amino acids and adopt the prefix adlo in their stead. The configu- 
rational designation and nomenclature of the y-hydroxyglutamic acids could thereby 
be represented as shown in Table III. 
As the configurations and optical rotations of each of the four antipodes of y-hydroxy- 
glutamic acid are now known, comparison of these with the optical rotation of the 
natural amino acid would suffice to establish the configuration of the latter. However, 
TABLE III 
CONFIGURATIONAL DESIGNATION AND NOMENCLATURE OF THE ISOMERIC 
VY-HYDROXYGLUTAMIC ACIDS 


Configuration of 
Isomer y-carbon atom Recommended designation 
y-Hydroxy-.t-glutamic acid A Ls OF Dg allo-y-Hydroxy-L-glutamic acid 
y-Hydroxy-p-glutamic acid A Ds OF Lg allo-y-Hydroxy-p-glutamic acid 
y-Hydroxy-L-glutamic acid B Ds OF Lg y-Hydroxy-.-glutamic acid 
y-Hydroxy-p-glutamic acid B Ls OF Dg y-Hydroxy-p-glutamic acid 
y-Hydroxy-L-glutamic acid (mol. wt. 163.1): 
[M]p = +31.8° (H,O) and +61.6° (5 N HCl);c = 1%,T = 2 
allo-y-Hydroxy-t-glutamic acid (mol. wt. 163.1): 
Vii pp —I—2 293° (Ei. @) andiet som (5 NEC] eo 195, fe —25-- 
On 
References p. 22/24 
