Hydrothermal formose reaction

The self-condensation of formaldehyde is a one pot reaction resulting in a complex mixture of carbohydrates. Based on a simple chemical, the reaction was previously considered as a prebiotic source for sugar generation. Usually, a high pH and the presence of catalytically active species are required. Here, the formose reaction was performed under hydrothermal temperatures up to 200 degrees C, and carbohydrates were obtained under even simpler conditions. We found no pronounced catalytic influence of active cations, and a slightly alkaline pH was sufficient to induce the reaction. Maximum yield was reached in very short times, partly less than 1 minute. No selectivity for a particular carbohydrate, although searched for, was found. Contrary to reactions performed at lower temperatures, hexoses were only formed in negligible yields, whereas the shorter carbohydrates accounted for the major fraction. Among the pentoses, ribose and the ketoses with corresponding stereochemistry were formed in higher yields compared to the reaction at lower temperature. Furthermore, we identified 2-deoxyribose in the product mix and found strong indications for the presence of other deoxy compounds. Hence, the hydrothermal formose reaction shows some remarkable differences compared to the conventional reaction at moderate temperatures.