MICROREVIEW DOI: 10.1002/ejoc.201001578 The Chemistry of L-Sorbose Ilhem Zebiri, [a] Sébastien Balieu, [a] Arnaud Guilleret, [b] Romain Reynaud, [b] and Arnaud Haudrechy* [a] Keywords: Carbohydrates / Protecting groups / Synthetic methods Despite the fact that L-sorbose has been widely used for the synthesis of vitamin C at an industrial level, its use in organic synthesis remains rare. However, a survey of the chemical Introduction -Sorbose (1, Scheme 1) is a readily available natural sugar, one of the rare ones in the -series. -sorbose is pro- duced by regiocontrolled dehydrogenation of -sorbitol by using Gluconobacter oxydans or Acetobacter species and its annual production is approximately 60000 tons. [1] Pro- duction from Gluconobacter oxydans or from other bacteria strains is limited by concomitant inhibition resulting from the presence of -sorbitol in amounts greater than 10% by mass of the reaction mixture. To avoid this, it has proven necessary to optimize the production method, thus render- ing industrial applications more attractive. [2] Scheme 1. Structure of -sorbose (1). -Sorbose has been largely used as a starting material in the synthesis of vitamin C and also in the formation of rare sugars, such as -tagatose by using -tagatose 3-epimerase isolated from Pseudomonas sp ST-24, [3] or -iditol by using Candida famata 234B. [4] Quite surprisingly, despite its structural similarity to well-exploited -fructose, few methods describing easy modification of this interesting sugar exist. [5] In the first part of this microreview, the different forms that -sorbose can adopt will be described (open, pyranose, or furanose), and in the second part, focus on chemical transformations and proposed additional synthetic possibilities will be high- lighted. [a] Institut de Chimie Moléculaire de Reims, UMR CNRS, Université de Reims, BP 1039, 51687 REIMS Cedex, France Fax: +33-326913166, E-mail: arnaud.haudrechy@univ-reims.fr [b] Soliance SA, Route de Bazancourt, 51100 Pomacle, France Eur. J. Org. Chem. 2011, 2905–2910 © 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2905 literature shows that this unusual sugar can be transformed into interesting derivatives. The Different Forms of L-Sorbose -Sorbose (1) can exist in an open form (Scheme 1), but it can also exist in two pyranose forms A (Scheme 2), where the α anomer is presumably the most favored due to the anomeric effect, which is further confirmed by experimental measurements in water between 27 and 85 °C (between 87 and 98 %); [6] all of those forms exist in equilibrium with two furanose forms B. Scheme 2. -Sorbose (1) and its four pyranose and furanose forms. Interestingly, in both pyranose forms, a maximum number of substituents occupy the equatorial positions, giving them a considerable thermodynamic stability (Scheme 3). Scheme 3. Pyranose forms of -sorbose. An interesting structural study was published that con- tradicts the statement that 1 exists predominantly in a pyra- nose form. [7] Indeed, oxidative cleavage of sorbopyranose form A with Pb(OAc) 4 should give an open intermediate (preferring the 1,2-syn diol system), followed by shortening