5.7 Branched Sugars
163
5.6.2
Acetals, Ketals
Derivatives of sugars generated by transformation of the carbonyl group
with alcohols are conventionally named as (hemi)acetals, (hemi)ketals
and so on.
SEt
I
H-C-OH
I
H-C-OAc
I
AcO-C-H
I
H-C-OAc
I
H-C-OAc
I
CH20Ac
CH20H
I
C(OEth
I
HO-C-H
I
H-C-OH
I
H-C-OH
I
CH20H
(1S)-2,3,4,5,6- Penta-O-ace- D-Fructosetyl-D-glucose S-ethyl modiethyl ketal
nothiohemiacetal
5.7
Branched Sugars
H H-C-OH
I
H-C-OH
I
H-C-OH
I
H-C-OH
I
CH20H
D-Allose-propane 1,3diyl dithioacetal
Branched monosaccharides are treated according to the afore-stated principles as substituted unbranched sugars, with customary trivial names
being retained. The chief criteria for the selection of parent saccharides
are:
a) the highest ranked functional type: aldaric acid> uronic acid/ketoaldonic acid/aldonic acid> dial dose > ketoaldose/aldose > diketose >
ketose,
b) the longest chain: heptose> hexose,
c) the alphabetically preferred parent system or configurational prefix:
allose> altrose; glueD > gulo,
d) the preferred configurational symbol: D > L; a > 13,
e) the parent system containing the largest number of substituents
expressed as prefixes.