Fischer convention<\/strong><\/p>\n\n\n\n The need for consistency in stereochemical designation prompted Emil Fischer to use C-5 of the dextrorotatory, (+)-, enantiomer of glucose as a starting point. This molecule was drawn in Fischer projection formula.<\/p>\n\n\n\n (+)-Glucose was degraded by Fischer to an aldotriose, (+)-Glyceraldehyde, in which the only stereogenic center originates from C-5 of the parent molecule. Arbitrarily, Fischer assigned the configuration (I)<\/strong> to (+)-Glyceraldehyde, which became D-(+)-Glyceraldehyde (OH on the right-hand side position) and the configuration (II)<\/strong> to (-)-Glyceraldehyde, which became L-(-)-Glyceraldehyde (OH on the left-hand side position).<\/p>\n\n\n\n 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. If the hydroxyl group attached to the highest chiral carbon<\/em><\/strong> is on the right-hand side it is referred to as D-series and if on the left-hand side it is called L-series. The configurational assignment based on chemically relating to chiral molecules to either D- or L-Glyceraldehyde is known as the genetic nomenclature.<\/p>\n\n\n\n Case study: Glucose<\/strong><\/p>\n\n\n\n Glucose is six carbon sugar (aldohexose). To apply Fischer convention focus on the placement of the -OH group attached to the highest chiral carbon (in this case C-5 (highlighted in red color).<\/p>\n\n\n\n In (+)-Glucose, the -OH group attached to the highest chiral carbon (C-5) is on the right-hand side of the carbon skeleton. Hence it is assigned the D-configuration. Whereas in the case of (-)-Glucose the -OH group attached to carbon (C-5) is on the left-hand side and hence assigned L-configuration.<\/p>\n\n\n\n Amino acid Convention \u2013 \u03b1-carbon<\/strong><\/p>\n\n\n\n The absolute configuration at the \u03b1-carbon atom of the \u03b1-amino acids is designated by the prefixed capital letter D or L to indicate a formal relationship to D- or L-serine and thus to D- or L-Glyceraldehyde. The configuration is determined by the location of amino group (-NH2) on alpha carbon of amino acid, if it is on right-hand side it is called D- amino acid and if it is on left-hand side then it is called L-amino acid.<\/p>\n\n\n\n <\/p>\n\n\n\n <\/p>\n\n\n\n Practice exercise<\/strong><\/p>\n\n\n\n Assign D-\/L- configuration to the following sugars and amino acid.<\/p>\n\n\n\n References<\/strong><\/p>\n\n\n\n Bernard Testa, Principles of organic stereochemistry, Marcel Dekker Inc., New York, 1979.<\/p>\n\n\n\n Hartung, Walter H.; Andrako, John (1961). “Stereochemistry”<\/a>. Journal of Pharmaceutical Sciences<\/em>. 50<\/strong> (10): 805\u2013818. doi:10.1002\/jps.2600501002<\/p>\n\n\n\n Slocum, D. W.; Surgarman, D.; Tucker, S. P. (1971). “The two faces of D and L nomenclature”. Journal of Chemical Education<\/em>. 48<\/strong> (9): 597. Bibcode:1971JChEd..48..597S. DOI:10.1021\/ed048p597<\/p>\n\n\n\n![\"\"](\"https:\/\/chiralpedia.com\/blog\/wp-content\/uploads\/2022\/03\/Glucose-1.png\")
![\"\"](\"https:\/\/chiralpedia.com\/blog\/wp-content\/uploads\/2022\/03\/Glyceraldehyde-DL-6.png\")
![\"\"](\"https:\/\/chiralpedia.com\/blog\/wp-content\/uploads\/2022\/03\/DL-Glucose-2.png\")
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![\"\"](\"https:\/\/chiralpedia.com\/blog\/wp-content\/uploads\/2022\/03\/Erthrose-Threose-Cycteine.png\")
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