a
CIPHERED FORMULAS IN CARBOHYDRATE CHEMISTRY ALVARO DIFINI and J O S ~ DIFINI NET0 Escola de Engenharia, Universidade do Rio Grande do Sul, P6rto Alegre, Brazil
MONOSACCHARIDES
To simplify the representation of monosaccharides, schematic formulas (geometrical simplifications) have been developed as an aid to a rapid writing of configurations. Hydroxyl groups at asymmetric carbon atoms have been indicated by horizontal lines joined to a vertical line. The intersections of the vertical and horizontal limes designate carbons, of a chain, that are usually asymmetric. Greater simplification can be attained by ciphered formulas (numerical simplifications). Hydrogen atoms projected t o the left of a vertical chain are indicated by the digit 1, whereas a hydroxyl radical to the left is represented by the digit 2. A comparison of the configurational, schematic and ciphered representations of acyclic D-glucose follows: CHO
for D-glycerose, "2" would be L-glycerose. An asymmetric carbon atom is identified by an asterisk. Aldotetroses would be formulated in this way: CHO
11 n-Erythrose
t:
I
* , HOH ( I or 2)
22 &Erythrose
*AHOH (1 or 2)
12 L-Threosej 21 D-Threosej
Enantiomorphs
Enantiornorphs
The configuration of an enantiomorph is obtained in a ciphered representation by interchanging each digit 1 with 2, and each 2 with 1. Ciphered formulas of monosaccharides belonging to the D-series terminate with 1 and those of the *series termiuate with 2. Examples of such representation among the ketohexoses are these (enantiomorphs are bracketed together):
0
I-
H - L1 o H
&HOH (1 or 2)
121 n-Sorbose 212 Ghrbose}
t:
* HOH (1 or 2 ) I
122 &Fructose 211 n-Fruotose)
CHIOH
Schematic
Configurational
Ciphered
I n order t o avoid ambiguity, some name must be given along with a ciphered formula, either a specific name or sometimes a general structural name. Starting with the aldotrioses, ciphered formulas could be employed: The ciphered formula "1" would stand
A summary of ciphered fornlulas of monosaccharides is given in Table 1. ALDITOLS AND ALDARIC ACIDS
Like the monosaccharides, the alditols can be represented by ciphered formulas, as long as the name of the
TABLE 1 Cinhered Formulas of Monosaccharides Aldotslroaea
11
Kclotelroaea
n-
1
Erythrose
22
r-
12
D .
L .
2
Glueoae L.
2122
L.
1212
L.
Idose
Threose 21
n-
1211
Erythrulose
D-
2121
n-
JOURNAL OF CHEMICAL EDUCATION
specific alcohol is given, or else the class name of alcohols to which it belongs. For example, the tetritols are represented by these ciphered formulas: ' ~ H O H( 1 or 2)
12 L-Threitol 21 D-Threital}
t:
* , HOH ( I or 2)
Since no aldehyde or ketone group is present, either one of the primary alcohol groups (-CH20H) can be placed a t the top of the chain of any given configuration by merely rotating the two-dimensional configurational formula through 180'. Thus many of the alditols can be indicated by two sets of digits. The second set is produced by exchanging a 1 for a 2, or a 2 for a 1, followed by inverting; this sometimes gives an identical set of digits. Aldaric acids also have identical ends (-COOH). Consequently, the ciphered formulas of aldaric acids are identical to those of the corresponding alditols. Aldaric acids are treated in the same way as the alditols. (Of course not all of the carbons marked with an asterisk are strictly asymmetric; some may be pseudoasymmetric.) COOH
I t is necessary to know that the ciphered formula refers to an aldaric acid or an alditol, or any other carbohydrate derivative with identical groups at both ends of the chain, before the ciphering takes on definite meaning. The ciphered representation of the alditols and aldaric acids are respectively summarized in Tables 2 and 3. MISCELLANEOUS APPLICATIONS
Equation writing can be expressed easily, as exemplified by the reduction of D-glucoseto D-glucitol:
or the isomerization of D-glucoseto D-fructose: D-Glucose base D-Fructose 1211 + 211
Reduction of D-sorboseproduces L-glucitol and D-iditol:
Alpha and beta modifications of carbohydrates can be represented in this way:
CHSOH
A
*( I HoH),
*IcHoH). I
Disaccharides like maltose and sucrose could be written as:
CIH,OH
~OOH Aldaric acids
Alditols
TABLE 2 Ciphered For ulas of Alditols Talntols
Pcnlitola
11 = 22
Ir
112 = 122
1-
Arabitol o-
221 = 211
Sucrose
Various modifications can be employed to take care of sugar derivatives like ethers, esters, and glycosides. These two formulas demonstrate such usage:
Ribitol
Threitol 21
Maltose
111 = 222
Erythritol
12
Hmilola
AcO-2
n-
i-0Ac I-OA c I-OAc 1 J -
I
CH20Ac a-D-Glucopyranose pentaacetate
121 = 212
Xylitol
1-OCHI CHIOCHZ :3,4,&Trimethyla-wmannopyrsnose
BIBLIOGRAPHY TABLE 3 Ciohered F o m u l a s of Aldaric Acids
mean-Tartaric soid
12
L .
Tartaric aoid 21
0-
Ribaric acid
112 = 122
L-
Arabinario acid 221 = 211
D-
1112 = 1222 L-
Talarie acid 2221 = 2111
1212
L-
Idarie acid 0-
2121
D-
FIESER,L. F., AND M. FIESER,"Organic Chemistry," 2nd cd., D. C. Heath and Co., Boston, 1950. GILMAN, H., Edilor, "Organic Chemistry," 2nd ed., John Wiley &Sons, Inc., New York, 1943, Vol. 2. Editors, "Advances in CarHUDSON, C. S., AND S. M. CANTOR, bohydrate Chemistry," Academic Press Inc., New York, 1950, Vol. 5. KARRER,P., "Tratado de Quimica Organica," Manuel Marin, Barcelona, 1944. NOVELLI.A,. "Quimica Organiea Acielica." Editorial El Ateneo, Buenos Aires, 1950. PERCIVAL,E. G. V., "Structural Cmhohydrate Chemistry," Frederick Muller Ltd.. London. 1950. PIGMAN, W. W., AND M. L. W ~ L F R O M , Edilom, "Advances in Carbohydrate Chemistry," Academic Press Inc., New York, 1945, 1948, 1949, Vols. 1, 3, 4. THOMAS, V., "Lepons de Chimie Organique," Dunod, Paris, 1932.
"Rules of Carbohydrate Namenclsture," 123rd A.C.S. Meeting, Chem. Eng. News, 31,177683, (1953).
VOLUME 35, NO. 1, JANUARY, 1958
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