Microwave-assisted chemistry of carbohydrates

Microwave irradiation is becoming an increasingly popular method of heating which replaces the classical one because it proves to be a clean, cheap, and convenient method. Often, it affords higher yields and results in shorter reaction times. This method of heating has been extended to almost all areas of chemistry with the exception of the carbohydrate chemistry which has suffered a certain delay, as it is testified by the limited number of applications. The aim of this review is to explore the variety of these applications in carbohydrate chemistry, even if in a limited number, which have been carried out with microwave irradiation as activating agent. Mainly, these concern the selective or unselective protection and deprotection of hydroxyl functionalities, and triglyceride alcoholysis and glycerolysis reactions of industrial interest since these lead to materials for the production of straining, emulsifying and softening agents and moreover for the production of an ecologic fuel (biodiesel). Other aspects of the carbohydrate chemistry such as the syntheses of monosaccharides containing heterocyclic nuclei, or unsaturations, or halogens are also included. Synthetically, the effect on the mutarotation phenomenon, polysaccharides, methanolysis and hydrolysis of saccharides, flavour formation deriving from the interactions of sugars with amino acids, and sterospecific activation of the C-H bond for the deuterium and tritium labelling are reported. In several cases, a comparison is made between results obtained with conventional and microwave-assisted methods.