Chemical and Functional Properties of Food Saccharides

© 2004 by CRC Press LLC
conditions. 35 Under alkaline conditions, 3-deoxy-2-hexosuloses, often called 3-deoxyhexosones,
are easily transformed into so-called metasaccharinic acids (18.24).
HC
COOH
CH 2
Formation of formic acid has also been reported. On the other hand, degradation of
3-deoxypentosone and 3-deoxytetrosone in alkaline solutions leads to rapid browning;
however, metasaccharinic acids are not detected. 35 Under acidic conditions, 5hydroxymethyl-2-furaldehyde
and 2-furaldehyde are formed as main products by
dehydration and cyclization of 3-deoxyhexosones and 3-deoxypentosones, respectively.
In the presence of larger amounts of primary amines, the formation of furan
derivatives is suppressed in favor of pyrrole (18.25) or pyridinium derivatives
(18.26). 36
CH 2
OH
a-Dicarbonyl cleavage and the so-called b-carbonyl route are other mechanisms
leading to the formation of furane and pyrrole derivatives from 3-deoxyosones. By
the former mechanism, 3-deoxyhexosuloses are transformed into 2-deoxypentoses
(18.27) that are further transformed into 2-hydroxymethyfurane (18.28) or 2hydroxymethylpyrroles
(18.29) (Reaction 18.8). The latter compounds have been
shown to have outstanding polycondensation potential. 37
HC
C
CH 2
O
O
HC OH
HC OH
CH 2 OH
F
HC
CH 2
CH 2
OH
O
HC OH
HC OH
CH 2 OH
18.17 18.27
Reaction 18.8
α-dicarbonyl
fragmentation
OH
HC OH
HC OH
CH 2 OH
18.24
N
R
18.25
CHO
-
O
N OH
+
R
18.26
H 2 O
HC
CH
CH
O
HC OH
CH 2 OH
H 2 O
R NH2 H O 2
O
28
N
R
18.29
CH 2
OH
CH 2
OH