Formose reaction
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.
Reaction and mechanism
The reaction is catalyzed by a base and a divalent metal such as calcium hydroxide. The intermediary steps taking place are aldol reactions, reverse Aldol reactions, and aldose-ketose isomerizations. Intermediates are glycolaldehyde, glyceraldehyde, dihydroxyacetone, and tetrose sugars. In 1959, Breslow proposed a mechanism for the reaction, consisting of the following steps:[3]
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 dihydroxyketone 3 which can react with 2 to form ribulose 4, and through another isomerization ribose 5. Molecule 3 also can react with formaldehyde to produce tetrulose 6 and then aldoltetrose 7. Molecule 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.
References
- ^ Butlerov, A. M. (1861). "Einiges über die chemische Structur der Körper". Zeitschrift für Chemie. 4: 549–560.
{{cite journal}}: Cite has empty unknown parameters:|month=and|coauthors=(help) - ^ Orgel, Leslie E. (2000). "Self-organizing biochemical cycles". PNAS. 97 (23): 12503–12507. doi:10.1073/pnas.220406697.
{{cite journal}}: Cite has empty unknown parameters:|month=and|coauthors=(help) - ^ Breslow, R. (1959). "On the Mechanism of the Formose Reaction". Tetrahedron Letters. 21: 22–26.
{{cite journal}}: Cite has empty unknown parameters:|month=and|coauthors=(help) - ^ Ricardo, A. (2004). "Borate Minerals Stabilize Ribose". Science. 303 (5655): 196. doi:10.1126/science.1092464.
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