5.1 Aldoses
157
Cyclic hemiacetal forms derived from these fundamental types are systematically named as ... ooxiroses (3-ring), ... ooxetoses (4-ring), ... ofuranoses (5-ring), ... opyranoses (6-ring), ... oseptanoses (7-ring), e.g.:
HO-C-H
CH20H
I
H-C-OH
I
H-Cfj-OH
I
H-C-O
I
HO-C-H
-
H-C-OH
I
HO-C-H
I
CH20H
[3-L-Glucooxetose
rH-C-OH
I
H-C-OH
I
HO-C-H
I
H-C-OH
I
H-C-OI
CH20H
a-D-Glucopyranose
~gf0
~H
rHO-C-H
I
H-C-OH
I
HO-C-H
I
H-C-OI
H-C-OH
I
CH20H
CH20H
I
HO-C-H
k~~H
4 OH
[3-D-Glucofuranose
HO-C-H
I
HO-C-H
I
H-C-OH
I
HO-C-H
I
HO-C-H
I
CH2 -O
a-L-Glucoseptanose
The configurational symbols a, [3 refer each to the so-called anomeric reference atom that in the above examples is identical with the configurational atom. Accordingly, the cis-relationship between the HO group
attached to the anomeric C atom and the oxygen attached to the reference
atom translates into a and trans into [3.
In reality, the cyclic hemiacetal forms of sugars and their derivatives
may assume a wealth of different ring conformations. For purposes of
nomenclature, however, linear Fischer Projections and Haworth Representations with their quasi conformation-averaging planar-cyclic habit
are best suited to illustrate the manifold stereochemical relationships significant for carbohydrates.
For the fundamental sugar types of Table 15 the respective trivial
names are generally preferred to the systematic names obtained according
to the pattern D-ribo-pentose (for D-ribose), D-gluco-hexose (for D-glucose), etc. For higher aldoses, however, exclusively systematic names are