Ascorbic acid - wiki

L-Ascorbic acid

Ascorbic acid is a naturally occurring organic compound with antioxidant properties. It is a white solid, but impure samples can appear yellowish. It dissolves well in water to give mildly acidic solutions. Ascorbic acid is one form ("vitamer") of vitamin C. It was originally called L-hexuronic acid, but, when it was found to have vitamin C activity in animals ("vitamin C" being defined as a vitamin activity, not then a specific substance), the suggestion was made to rename it. The new name, ascorbic acid, is derived from a- (meaning "no") and scorbutus (scurvy), the disease caused by a deficiency of vitamin C. Because it is derived from glucose, many non-human animals are able to produce it, but humans require it as part of their nutrition. Other vertebrates which lack the ability to produce ascorbic acid include some primates, guinea pigs, teleost fishes, bats, and some birds, all of which require it as a dietary micronutrient (that is, in vitamin form).

Ascorbic acid is prepared in industry from glucose in a method based on the historical Reichstein process. In the first of a five-step process, glucose is catalytically hydrogenated to sorbitol, which is then oxidized by themicroorganism Acetobacter suboxydans to sorbose. Only one of the six hydroxy groups is oxidized by this enzymatic reaction. From this point, two routes are available. Treatment of the product with acetone in the presence of an acid catalyst converts four of the remaining hydroxyl groups to acetals. The unprotected hydroxyl group is oxidized to the carboxylic acid by reaction with the catalytic oxidant TEMPO (regenerated by sodium hypochlorite —bleaching solution). Historically, industrial preparation via the Reichstein process used potassium permanganate as the bleaching solution. Acid-catalyzed hydrolysis of this product performs the dual function of removing the two acetal groups and ring-closing lactonization. This step yields ascorbic acid. Each of the five steps has a yield larger than 90%.

A more biotechnological process, first developed in China in the 1960s, but further developed in the 1990s, bypasses the use of acetone-protecting groups. A second genetically modified microbe species, such as mutant Erwinia, among others, oxidises sorbose into 2-ketogluconic acid (2-KGA), which can then undergo ring-closing lactonization via dehydration. This method is used in the predominant process used by the ascorbic acid industry in China, which supplies 80% of world's ascorbic acid.^[30] American and Chinese researchers are competing to engineer a mutant that can carry out a one-pot fermentation directly from glucose to 2-KGA, bypassing both the need for a second fermentation and the need to reduce glucose to sorbitol.

Historically important industrial synthesis of ascorbic acid from glucose via the Reichstein process. 

This process was patented and sold to Hoffmann-La Roche in 1935. The first commercially sold vitamin C product was called Cebion from Merck.

The Reichstein process in chemistry is a combined chemical and microbial method for the production of ascorbic acid from D-glucose that takes place in several steps. This process was devised by Nobel Prize winner Tadeus Reichstein and his colleagues in 1933 while working in the laboratory of the ETH in Zürich.

Tadeusz Reichstein (20 July 1897 – 1 August 1996) was a Polish bornchemist, naturalized Swiss and the Nobel Prize in Physiology or Medicinelaureate (1950).

F. Hoffmann-La Roche AG is a Swissglobal health-care company that operates worldwide under two divisions: Pharmaceuticals andDiagnostics. Its holding company, Roche Holding AG, has bearer shares listed on the SIX Swiss Exchange.

The Merck Group, branded and commonly known as Merck, is a German multinational chemical, pharmaceutical and life sciences company headquartered in Darmstadt, with around 50,000 employees in around 70 countries. Merck was founded in 1668 and is the world's oldest operating chemical and pharmaceutical company, as well as one of the largest pharmaceutical companies in the world.

Further reading:

2-cyanopicolinium esters could be reductively cleaved using Ru(bpy)₃²⁺ and ascorbic acid under visible light irradiation.

[HTML] Visible light photoredox catalysis: applications in organic synthesis

JMR Narayanam, CRJ Stephenson - Chemical Society Reviews, 2011

 924

[HTML] rsc.org

As the reductant, ascorbic acid and/or sodium ascorbate proved to be excellent for they allow preparation of a broad spectrum of 1,4-triazole products in high yields and purity at 0.25–2 mol % catalyst loading.

A stepwise huisgen cycloaddition process: copper (I)‐catalyzed regioselective “ligation” of azides and terminal alkynes

VV Rostovtsev, LG Green, VV Fokin, KB Sharpless - Angewandte Chemie, 2002

7697

In situ synthesis of gold nanoparticles using molecular gels and liquid crystals from vitamin-C amphiphiles

P Kumar Vemula, U Aslam, V Ajay Mallia, G John - Chemistry of materials, 2007

103

[PDF] cuny.edu