OCCURRENCE OF FREE AMINO ACIDS — PLANTS Fas 
DISCUSSION 
Chairman: EUGENE ROBERTS 
POLLARD: Recently, we have repeated the isolation of an amino acid from Phlox, which was first 
described by VIRTANEN AND Hierara!. Although the optical rotation was not determined by 
VIRTANEN, this substance was characterized chemically as y-hydroxyglutamic acid. The original 
published analysis showed that this particular y-hydroxyglutamic acid was not a hydrate and 
could be presumed to be identical with y-hydroxyglutamic acid “A”, later synthesized and resolved 
by Brenorton et al. (cf. Winttz’s contribution to this symposium). FowDEN® has also isolated 
y-hydroxyglutamic acid from Hemerocalis and has determined its optical rotation. With Dr. WINITz’s 
assistance, we have also determined the optical properties of the y-hydroxyglutamic acid in Phlox. 
Consequently, by all the criteria now proposed, the y-hydroxyglutamic acid from Phlox is found 
to be identical with the synthetic material called by BEeno1ton ef al. “L-allo-y-hydroxyglutamic 
acid”. 
The term allo was applied to this particular isomer because it was correlated stereochemically 
with L-allo-y-hydroxyproline. This use of the term allo really implies more stereochemical signifi- 
cance than the term usually conveys. Allo simply means “the other one’. Wherever possible, 
as in the case under discussion, the term should be used to designate that isomer, whatever its 
absolute configuration, which is different from the first discovered isomer, in this case, a natural 
product. Since no absolute rule governs the assignment of the term allo, some element of choice 
remains. However, the most important thing is the determination of absolute structure in the 
manner for which Dr. Win1rz stands. Therefore, so long as the absolute structure is unequivocally 
established, the choice of names, within the existing framework of rules, remains somewhat 
secondary so that the name as proposed by BENoiToN e¢ al. can certainly be retained. However, 
it is suggested that this use of the term allo should not become a precedent to cover generally a 
structural relationship with some other allo compound, for if this were adopted, the original 
usefulness of the term would be lost. 
Win11z: With regard to Dr. PoLLARD’s comments concerning the nomenclature of the y-hydroxy- 
glutamic acids, it will be recalled that y-hydroxyglutamic acid was first discovered in nature by 
VIRTANEN in about 1955. As its configuration and optical rotation were not then ascertained, there 
was no way of knowing which of the four possible stereoisomers it actually represented. Such was 
the situation in 1957 when we prepared the material synthetically, separated the racemic dia- 
stereomers, labeled one racemate “A” and the other “B” according to the FiscHER convention, 
resolved each racemate, and then correlated the configurations of the antipodes of the A and B 
forms with those of the antipodes of hydroxyproline and allohydroxyproline. Some four years 
later, only a few short weeks ago, the material was isolated by STEWARD AND POLLARD from Phlox 
decussata seed, and it was found that the rotation of this natural material corresponded to that 
of the synthetic antipode to which we had previously assigned the designation of allo-~y-hydroxy- 
L-glutamic acid. Now, Dr. PoLLarp presumes to question the use of the term allo in this situation 
because neither does its application to the naturally occurring form appeal to his esthetic senses 
nor were we prophetic enough to predict the optical identity of the natural material some four 
years prior to its actual characterization. 
It should be emphasized that the term allo has no configurational meaning whatsoever. It just 
means the other form, and it makes no difference whether we designate the natural form as allo 
or normal as long as there is no confusion with regard to its optical configuration. In this connec- 
tion, it should be recalled that both the normal and allo forms of several amino acids, such as the 
hydroxyprolines and the isoleucines, have been found in nature. It should further be recalled that 
ADAMS AND GOLDSTONE demonstrated that an enzyme from mammalian tissues converts hydroxy- 
proline to the normal form of y-hydroxyglutamic acid; allohydroxyproline, however, was not 
susceptible to the action of this enzyme and not converted to the allo-y-hydroxyglutamic acid 
isolated from plants. It is obvious, therefore, that the use of the designations of normal and allo 
in connection with the natural occurrence of a given amino acid not only has no significance, but 
is a use for which these terms were never intended. 
AXELROD: The isolation of 6-aminoisobutyric has been mentioned. I should just like to add an 
References p. 72 
