48 L. FOWDEN AND D- ©. GRAY 
The metabolism of the substituted amides has not been investigated in plants as 
yet. It would seem reasonable to assume that deamidase-type enzymes would hydrolyse 
them to give products identical with those obtained after acid hydrolysis. Biosyn- 
thetic pathways leading to the amides may be dependent upon synthetase-type 
enzymes utilizing aspartic acid and ethylamine or ethanolamine as substrates (compare 
glutamine and asparagine synthetases), or upon transferase-type enzymes where 
asparagine and the appropriate amine would act as substrates (compare the action 
of glutaminotransferase upon mixtures of glutamine and hydroxylamine). 
Extracts of fresh rat liver, which are known to possess strong asparaginase activity 
(GREENSTEIN AND CARTER?®), hydrolysed compounds VIII and IX more slowly than 
asparagine; aspartic acid together with either ethylamine or ethanolamine were 
identified as reaction products. Although the degradation of asparagine is also catalysed 
by transaminases when keto acids are added to liver extracts (GREENSTEIN AND 
CARTER®®; MEISTER, SOBER, TICE AND FRASER®®), the addition of pyruvate did not 
cause a noticeable increase in the rate of breakdown of the substituted asparagines. 
The two amides were synthesized chemically by a similar method in which an etha- 
nolic solution of 4-ethyl hydrogen-L-aspartate, prepared by the method of CurRTIS 
AND Kocu*!, was heated for several hours at 100° with either ethylamine or ethanol- 
amine. Natural and synthetic products were shown to be identical by comparisons 
of m.p., Rp, and [a|p and by infrared spectroscopy. 
Our observations have indicated that several additional, unidentified amino acids 
are present in bryony and in other members of this family of plants. 
Cyclopropylamino acids from the family Sapindaceae 
Hypoglycin A (XIII), isolated from the fruits of the tropical plant, Blighia sapida, 
has been a centre of interest because it possesses both an intriguing chemical structure 
and a distinct physiological action in reducing the blood sugar levels of animals 
(HASSALL AND REYLE*, 33; PaTRIcK**). Its structure was elucidated by work in 
several different laboratories (ANDERSON et al. 9°; VON HOLT AND LEPPLA®®; RENNER, 
JOHL AND STOLL??; DE Ropp, VAN METER, DE RENzO, MCKERNS, PIDACKS, BELL, 
ULLMAN, SAFIR, FANSHAWE AND Davis?8; WILKINSON??; ELLINGTON, HASSALL AND 
PLIMMER”) and has been confirmed by chemical synthesis. Now we have shown an 
analogous amino acid, a-(methylenecyclopropyl)glycine (XIV), to be a constituent 
of the fruit of the subtropical species, Litchi chinensis. 
CHY=¢ CH—CH,-CH(NH,)-COOH CH CH—CH(NH,):COOH 
\CH,/ XII \CH,/ XIV 
XIV was detected in extracts of Litchi seeds by paper chromatography ; the extract 
contained an acid which moved to a position between y-aminobutyric acid and valine 
on chromatograms developed with a n-butanol-acetic acid—-water mixture (see Table I 
for R; in phenol). The ninhydrin colour was brown initially but changed to violet 
over a period of 2h. The crude acid (1.35 g) was isolated from 24 kg of fresh seeds 
(water content approx. 50°) by ion-exchange and paper-partition chromatographic 
methods. After recrystallization from 70% (v/v) ethanol, 0.68 g of pure compound 
was obtained; decomposition began at 202°, [a]p?!> + 83.5° (c = 3.0% in water), 
[a]p + 110° (c = 2.5% in 5 N HCl). 
References p. 53 
