50 L. FOWDEN AND D. O. GRAY 
than the other two isomers. The two earliest reduction products are presumably 
formed after uptake of only two hydrogen atoms, and represent geometrical isomers 
of a-(methylcyclopropyl)glycine (XV and XVI). The major isomer (XV, Fig. 2) was 
isolated by paper chromatographic methods from the mixture of amino acids resulting 
after hydrogenation of 75mg of a-(methylenecyclopropyl)glycine. Elementary 
analysis "gave? "C4912 955) Hy 8:7 62 N}; Q096 C,H NO; HO mequires Guioqoe 
H, 8.8%; N, 9.5%. The reduction sequence may then be written as: 
H 
abr CH,—C CH-CH(NH,)-COOH 
\ / 
Seer XIV 
GH a el 
§ : 
x ___CH-CH(NH,)-COOH <— _> CH,:(CH,),-CH(NH,)-COOH 
FR EEN 2 
HCH, _ XIX 
2 3 Norleucine 
CHy-CHay 
Earl ee ) CH-CH(NH,)-COOH 
XV and XVI . =a CH 
XVII 
Isoleucine 
H 1 
CHa 
—> C———CH-CH(NH,)-COOH <— ak a CH-CH,:CH(NH,)-COOH 
« a es F 3/ 
cH,” ° CH, XVIII 
2 3 Leucine 
When hypoglycin A was hydrogenated under identical conditions, the time-course of 
the reaction showed the production of a similar series of amino acids, each moving 
slightly faster on paper chromatograms than the corresponding product from XIV, a 
behaviour characteristic of a series of homo-amino acids. 
Whilst the infrared spectra indicated that the C=C was probably exocyclic, the 
hydrogenation results did not provide critical evidence to eliminate other possible 
structures, e.g. XX, XXI and XXII, below: 
CH,—CH——C-CH(NH,):COOH CH.—G C:CH(NH,)-COOH 
.CHY NCH, ~ 
OK Od 
CH 6 CH-CH(NH,)-COOH 
\CH~ 
SO 
However, the nuclear magnetic-resonance spectrum of the compound dissolved in 
CF,COOD (determined and interpreted by Dr. ABRAHAM, National Physical Labor- 
atory, Teddington) eliminated these possibilities and supported structure XIV as the 
only one fitting all the experimental observations. 
The stereochemical configuration of the two asymmetric carbon atoms was deter- 
mined by isolation of the isoleucine produced by catalytic hydrogenation. We have 
References p. 53 
