SOME AMINO ACIDS FROM PLANTS Bye 
found that it is possible to separate isoleucine from alloisoleucine on paper chromato- 
grams (Whatman No. 3MM paper) developed for 4 or 5 days ina tert.-amyl alcohol- 
water—acetic acid mixture (20 : 20 : I, v/v; upper phase used; isoleucine runs slightly 
faster than alloisoleucine) and in this way the isolate was shown to be isoleucine. 
This isoleucine had [a]p + 43 + 6° (c = 0.5% in 5 N HCl); authentic L-isoleucine 
has [a]p + 39.5° (c = 0.5-2.0% in 5 N HCl). The four stereoisomers of a-(methyl- 
SE45: SO ui NOMS Som Ons 
P+} 4 tt tt 4 4 4 


Fig. 2. A diagrammatic representation of a chromatogram, developed in f-amyl alcohol—water— 
acetic acid (20 : 20 : I, v/v, upper phase), produced from samples of the reaction mixture obtained 
after the hydrogenation of a-(methylenecyclopropyl)glycine for various times (expressed in min 
at the origin of the chromatogram). The spots were identified as: XIV, a-(methylenecyclopropy])- 
glycine; XV and XVI, geometrical isomers of a-(methylcyclopropyl)glycine; XVII, isoleucine; 
XVIII, leucine; and XIX, norleucine. 
enecyclopropyl)glycine are represented using Fischer’s convention by structures 
XXIII-XXVI; the appropriate isoleucine isomer that would be obtained after 
hydrogenation is listed below each representation. Structure XXIV represents the 
natural isomer isolated from Litchi seeds. 
The L-configuration at the a-carbon atom is supported by the observation that the 
value of [a], measured for an a-(methylenecyclopropyl)glycine solution in 5 N HCl 
had a higher (+) value than when the determination was made in aqueous solution. 
As yet we have not been able to assign exact stereochemical configurations to the 
CH, CEH, CH, GE: 
GS Cn CS ZG 
et : Se 
CH, CH, (Ciel, CH 
er ae * Ee Cn 
H,N—C—H H—C—NH, H,N—C—H H—C—NH, 
COOH COOH COOH COOH 
XXITI XXIV XXV XXVI 
D-isoleucine L-isoleucine p-alloisoleucine L-alloisoleucine 
References p. 53 
