4.2 Monosaccharides 273formation of l-deoxy-2,3-diulose, also called
1-deoxyosone. In addition,4-deoxy-2,3-diulose,
also called 4-deoxyosone, can be formed by
water elimination at C-4 of 2,3-eneaminol
(Formula 4.57). In contrast to the previously
mentioned pathways, the amino acid residue re-
mains bound to the carbohydrate in this reaction
path. As shown in the reaction scheme, all three
deoxyosones occur in different cyclic hemiacetal
forms.
As in the case of the deoxyosones, the concen-
trations ofAmadoriandHeynscompounds vary,
depending on the reaction conditions (pH value,
temperature, time, type and concentration of
the educts). As a result, there is a change in the
product spectrum and, consequently, in the color,
taste, odor, and other properties of the food in
each case.
(4.54)(4.55)(4.56)Like allα-dicarbonyl compounds, deoxyosones
can be stabilized as quinoxalines by a trapping re-
action with o-phenylenediamine (Formula 4.58)
and subsequently quantitatively determined using
liquid chromatographic techniques. In this way,
deoxyosones were detected for the first time as
intermediates in carbohydrate degradation.
The stable secondary products of theMaillardre-
action, that are isolated from many different re-
action mixtures and have known structures, can
be generally assigned to a definite deoxyosone by
a series of plausible reaction steps (enolization,
elimination of water, retroaldol cleavage, substi-
tution of an amino function for a hydroxy func-
tion etc.).
Of the large number of secondary products known
today, a few typical examples will be dealt with
here for each deoxyosone.