Food Chemistry

17.1 Vegetables 781

to ketoglutarate in theKrebscycle:

(17.1)

4-Methyleneglutamic acid (Table 17.5: XXXI) is
formed from pyruvic acid:

(17.2)

The important precursors of onion flavor, the

S-alkylcysteine sulfoxides, are formed as follows:

(17.3)

2,4-Diaminobutyric acid and some other

compounds are derived from cysteine (cf. Reac-

tion 17.4).

The aspartic acid semi-nitrile formed initially

can be decarboxylated toβ-amino propionitrile

which, just as its γ-glutamyl derivative, is

responsible for osteolathyrism in animals.

Hydrolysis of the semi-nitrile yields aspartic acid,

hydrolysis and reduction yield 2,4- diaminobu-

tyric acid, the oxalyl derivative of which, like

oxalyldiaminopropionic acid, is a human neu-

rotoxin. The main symptoms of neurolathyrism

are paralysis of the limbs and muscular rigidity.

2,4-Diaminobutyric acid can be converted via the

aspartic acid semialdehyde into 2-azetidine car-

boxylic acid (XXI), which occurs, for example,

in sugar beets (Table 17.5).

(17.4)