Chemistry Reference
In-Depth Information
'sugar' goes back to the Sanskrit word '
sarkar
', which means sugar cane and its
product. This word has entered many languages (for example Persian, Greek, Latin
and Arabic). The Greek variant '
saccharon
'
and its Latin form '
sac-
charum
' have led us to designate sugars as 'saccharides'. When using 'glycoside',
the Greek term '
glykys
'
(
σ
κχαρον
)
(
γλυκ ς
)
, translated into ' sweet ' , is the etymological
root.
The most abundant hexose is glucose (Glc) or grape sugar. Its name is derived
from the Latin loanword ' glucus ' . This sugar and its 2 - deoxy - 2 - acetamido deriva-
tive
N
-acetylglucosamine (GlcNAc) are the building blocks for rigid cell walls, that
is, the polymers cellulose and chitin (please see Chapter 12 for details). GlcNAc
is ubiquitously present in glycosaminoglycan chains and peptidoglycans as well
as in glycoconjugates such as glycoproteins with
N
- and
O
- glycans (please see
Chapters 6 - 11 and 29 ). De -
N
-acetylation without proper sulfation results in the
occurrence of small amounts of glucosamine ( GlcN ) in glycosaminoglycan chains
(please see Chapter 11). Historically, the scientifi c detection of the natural pres-
ence of GlcN and its derivative GlcNAc dates back to a fortunate menu selection
in 1875 (see Info Box 1 and also Info Box 1 in Chapter 12). An answer why glucose
and its derivatives are so abundant in Nature is given in the next paragraph by
closely looking at the different projection formulas.
Info Box 1
'In 1875 a young physician named Georg Ledderhose was working during the
summer semester in the laboratory of Friedrich Wöhler in Göttingen when
Ledderhose's uncle, Felix Hoppe-Seyler, a noted physiological chemist, invited
him to dinner. At his uncle's suggestion he took the remains of the lobster they
had eaten back to the laboratory, where he found that the claws and the shell
dissolved in hot concentrated hydrochloric acid and that on evaporation the
solution yielded characteristic crystals. He soon identifi ed the crystalline com-
pound as a new nitrogen-containing sugar, which he named
glycosamin
' [N.
Sharon. Carbohydrates.
Sci Am
1980;
243
, 80 - 97].
Note: F. Hoppe-Seyler was the founder of the
Zeitschrift fü r physiologische
Chemie
in June 1877, which today is known as
Biological Chemistry
.
1.2
What Projection Formulas Tell Us
The classical chain structure introduced by E. Fischer fi gures how the (H
2
O)
m
molecules are distributed over the carbon backbone. A series of hydroxy groups
is present together with an aldehyde function at C1 (Figure 1.1a). Of note, their
high density establishes a platform with exceptional properties (please see below).
When looking at experimental numbers in Figure 1.2, it becomes obvious that the
chain structure will not at all be the predominant form of a carbohydrate.
