The formose reaction, discovered by Aleksandr Butlerov in 1861[1][2], involves the formation of sugars from formaldehyde. Formose is a contraction of formaldehyde and aldose.
The reaction begins with two formaldehyde molecules condensing to make glycolaldehyde 1 which further reacts in an aldol reaction with another equivalent of formaldehyde to make glyceraldehyde 2. An aldose-ketose isomerization of 2 forms dihydroxyketone3 which can react with 2 to form ribulose4, and through another isomerization ribose5. Molecule 3 also can react with formaldehyde to produce tetrulose6 and then aldoltetrose7. Intermediate 7 can split into 2 in a retro-aldol reaction.
Significance
The formose reaction is of importance to the question of the origin of life as it is a path from simple formaldehyde to complex sugars like ribose and from there to RNA. In one experiment simulating early Earth conditions, pentoses formed from mixtures of formaldehyde, glyceraldehyde, and borate minerals such as colemanite Ca2B6O115H2O or kernite Na2B4O7.[4] Adding to the interest in the formose reaction is the fact that both formaldehyde and glycolaldehyde have been observed spectroscopically in outer space.
