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| Home > JCE Print > Journal of Chemical Education > Issues >
1999
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January
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In the Laboratory
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Use of Protecting Groups in Carbohydrate Chemistry: An Advanced Organic Synthesis Experiment
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Anna C. Cunha, Leticia O. R. Pereira, Maria Cecília B. V. de Souza, and Vitor F. Ferreira
Universidad Federal Fluminense, Instituto de Química, Departamento de Química Organica, CEG, Campus do Valonguinho, Rio de Janeiro, Niterói 24020-150, Brazil
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January 1999
Vol. 76 No. 1
p. 79
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| Abstract |
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A simple and inexpensive three-step reaction sequence for advanced experimental organic chemistry using D-glucosamine hydrochloride as starting material for the synthesis of 2-amino-2-deoxy-1,3,4,6-tetra-O-acetyl-b-D-glucopyranose hydrochloride is described. D-Glucosamine hydrochloride is a carbohydrate derivative isolated from crab shells. It is inexpensive and readily available from most chemical companies. This reaction sequence is appropriate for teaching undergraduate students the correct use of protecting groups. This is a major concept in organic synthesis and one of the determinant factors in the successful realization of multiple-step synthetic projects. The aim of the experiment is to protect the hydroxyl groups of D-glucosamine leaving its amino group as hydrochloride salt. The experiment deals only with protection and deprotection reactions. All products are crystalline substances. The amino group of d-glucosamine hydrochloride is protected by a condensation reaction with p-methoxybenzaldehyde to produce the Schiff's base as a mixture of a- and b-anomers. The second step involves the protection of all hydroxyl groups by esterification reaction using acetic anhydride, forming the imino-tetraacetate derivative as the b-anomer. The stereospecificity of this reaction at the anomeric center is due to the voluminous imino group at C-2. Removal of the amino protection group of this derivative is the final step, which can be accomplished by a selective acid hydrolysis affording the desired peracylated D-glucosamine hydrochloride.
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| More Information |
 Citation |
Cunha, Anna C.; Pereira, Leticia O. R.; de Souza, Maria Cecília B. V.; Ferreira, Vitor F. J. Chem. Educ. 1999 76 79.
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Keywords |
Organic Chemistry; Carbohydrates; Undergraduate Research; Organic Synthesis; Teaching/Learning Theory/Practice; Laboratory Instruction
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History |
Created:
Last Updated: |
June 15, 1999
June 22, 2005
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| Home > JCE Print > Journal of Chemical Education > Issues >
1999
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January
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79
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