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l-Glucose is an organic compound with formula C 6 H 12 O 6 or O=CH[CH(OH)] 5 H, specifically one of the aldohexose monosaccharides. As the l-isomer of glucose, it is the enantiomer of the more common d-glucose. l-Glucose does not occur naturally in living organisms, but can be synthesized in the laboratory.
There are three common naming conventions for specifying one of the two enantiomers (the absolute configuration) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents d- and l-) is based on its optical rotation properties; and the D/L system is based on the molecule's relationship to ...
Of note, the L form of amino acids and the D form of sugars (primarily glucose) are usually the biologically reactive form. This is due to the fact that many biological molecules are chiral and thus the reactions between specific enantiomers produce pure stereoisomers. [5] Also notable is the fact that all amino acid residues exist in the L form.
L-forms of amino acids tend to be tasteless, whereas D-forms tend to taste sweet. [13] Spearmint leaves contain the L-enantiomer of the chemical carvone or R-(−)-carvone and caraway seeds contain the D-enantiomer or S-(+)-carvone. [9] The two smell different to most people because our olfactory receptors are chiral.
The use of capital letters is to differentiate from the "d" / "l" notation (optical descriptor) described earlier. In this system, the enantiomers are named with reference to D- and L-glyceraldehyde which is taken as the standard for comparison. The structure of the chiral molecule should be represented in the Fischer projection formula.
The lowercase "d-" and "l-" prefixes are distinct from the SMALL CAPS "D-" and "L-" prefixes. The " D -" and " L -" prefixes are used to specify the enantiomer of chiral organic compounds in biochemistry and are based on the compound's absolute configuration relative to (+)- glyceraldehyde , which is the D -form by definition.
The D/L system (named after Latin dexter and laevus, right and left), not to be confused with the d-and l-system, see above, does this by relating the molecule to glyceraldehyde. Glyceraldehyde is chiral itself and its two isomers are labeled D and L (typically typeset in small caps in published work). Certain chemical manipulations can be ...
The fact that d-glucose is dextrorotatory is a combined effect of its four chiral centres, not just of C-5; some of the other d-aldohexoses are levorotatory. The conversion between the two anomers can be observed in a polarimeter since pure α-d-glucose has a specific rotation angle of +112.2° mL/(dm·g), pure β-d-glucose of +17.5° mL/(dm·g ...