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Synlett 2009(5): 848-849  
DOI: 10.1055/s-0028-1087718
SPOTLIGHT
© Georg Thieme Verlag Stuttgart ˙ New York

l-Ascorbic Acid

Bernhard Füger*
Institute of Organic Chemistry, RWTH Aachen University, ­Landoltweg 1, 52056 Aachen, Germany
e-Mail: bernhard.fueger@oc.rwth-aachen.de;
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Publikationsdatum:
24. Februar 2009 (online)

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Introduction

l-ascorbic acid, also known as Vitamin C, has an important role in physiology. As an essential vitamin, it has to be taken regulary by mammals which cannot produce it themselves. It serves to prevent deseases and has proven to act beneficially in the human body. Moreover, it is used in large amounts in the food industry as a nutritional additive and as a radical scavenger to e.g. prevent the oxidative degradation of lipids in food. The oxidation of l-ascorbic acid (or its monoanion 1) proceeds via monodehydro-l-ascorbic acid (radical anion 2), which disproportionates to l-ascorbate (1) and dehydro-l-ascorbic acid (3) (Scheme  [¹] ). [¹]

Scheme 1

l -ascorbic acid can be synthesized in large amounts from d-glucose by a combination of chemical and microbiological steps in an overall yield of 66%. [²]

Despite its physiological significance, the chemistry of ­l-ascorbic acid remained unexplored for a long time. This is probably due to its many reaction possibilities and the resulting lack of chemo- and/or regioselectivity. Procedures for selective functionalization of l-ascorbic acid had to be developed before any further utilization was possible. For example, highly regioselective O-alkylation was described recently: 5,6-Ο-Isopropylidene protected l-ascorbic acid 4 reacts with many electrophiles to yield 2-O-substituted products 5 or 3-O-substituted products 6 in excellent yields and regioselectivities, depending on the reaction conditions (Scheme  [²] ). [³]

Scheme 2