Uronic acids are carbohydrates present in relevant biologically active compounds. Most of the latter are glycosides or oligosaccharides linked by their anomeric carbon, so their synthesis requires glycoside-bond formation. The activation of this anomeric center remains difficult due to the presence of the electron-withdrawing C-5 carboxylic group. Herein we present an overview of glucuronidation, mannuronidation and galacturonidation reactions, including syntheses of prodrugs, oligosaccharides and stereochemical aspects.

The microwave-assisted alkaline degradation of D-glucose with alumina supported potassium hydroxide towards its conversion into lactic acid is reported. An experimental design approach was used to optimize the variables involved in this transformation. The reaction succeeded in yielding 75C-% of lactic acid starting from D-glucose using 1.5 equiv of KOH at 180 °C. The optimal conditions were applied to D-fructose, D-mannose and D-sucrose.

A mecanosynthesis of glycosylamines under solventless conditions was established. This environmentally friendly approach optimized with l-rhamnose, was investigated using a variety of amines and other carbohydrates.

In the growing context of sustainable chemistry, one of the challenges of organic chemists is to develop efficient and environmentally friendly methods for the synthesis of high-added-value products. Heterogeneous photocatalytic transformations have brought revolution in this regard, as they take advantage of an unlimited source of energy (solar light) or artificial UV light to onset organic chemical modifications. The abundance of free carbohydrates as chemical platform feedstock offers a great opportunity to obtain a variety of industrial interest compounds from biomass. Due to their chirality and polyfunctionality, the conversion of sugars generally requires multi-step protocols with protection/deprotection steps and hazardous chemical needs. In this context, several selective and eco-friendly methodologies are currently under development. This review presents a state of art of the recent accomplishments concerning the use of photocatalysts for the transformation and valorization of free carbohydrates. It discusses the approaches leading to the selective oxidation of free sugars, their degradation into organic chemicals, or their use for hydrogen production.