Self-condensation reactions, sugar

Acid or Lewis-acid catalyzed self-condensation reactions of 1,2-anhydro sugars were studied for the synthesis of polysaccharides [438]. Polysaccharides of relatively low molecular weights (< 10,000) were obtained, and the anomeric configurations could be varied depending on the promoter and temperature [439]. 

Another example of the ability of proteinogenic amino acids, small peptides, and amines to catalyse the formation of new C-C bonds has been demonstrated by Weber and Pizzarello they were able to carry out model reactions for the stereospecific synthesis of sugars (tetroses) using homochiral L-dipeptides. The authors achieved a D-enantiomeric excess (ee) of more than 80% using L-Val-L-Val as the peptide catalyst in sugar synthesis (in particular D-erythrose) via self-condensation of glycol aldehyde. 

Knowledge of the reaction conditions on primitive Earth is essential to carry out laboratory investigations, and neither proteins nor nucleic acids form spontaneously in aqueous solution (47). Sugars must have been formed by the self condensation of formaldehyde, another possible precursor of life, via the photolysis of water in the presence of CH4. 

---