Chemistry Reference
In-Depth Information
Chapter 2
The Role of Silicates in the Synthesis of Sugars
Under Prebiotic Conditions
Joseph B. Lambert, Senthil Andavan Guruswamy-Thangavelu
2.1
Sugars and Life
Before life, there must have been the molecules of life—amino acids for proteins, het-
erocyclic bases such as adenine for nucleic acids, and sugars for polysaccharides. In
1953, Miller demonstrated that amino acids could be produced from mixtures of
water, carbon monoxide, ammonia, and hydrogen with the help of an electric spark
[
1
]. Oró and Kimball were able to prepare the nucleotide base adenine from
hydrogen cyanide and ammonia [
2
]. Many advances on these experiments have
been made in the subsequent decades. In 1967 Gabel and Ponnamperuma reported
experiments indicating that simple sugars could be prepared from formaldehyde,
based on the Butlerov reaction [
3
]. Breslow in 1959 already had provided an aldol
mechanism for this reaction [
4
]. Reid and Orgel, however, in a companion paper
to that of Gabel and Ponnamperuma, concluded that the Butlerov reaction was im-
practical because the sugars decompose and “some method of stabilizing the sugars
is essential” [
5
]. The authors respectively used aluminosilicates and a mixture of
carbonate and hydroxyapatite, but obtained yields under 5 % of unstable sugars.
2.2
The Formose Reaction
The Butlerov reaction (Fig.
2.1
) had come to be known as the formose reaction, as it
converts formaldehyde to sugars (-oses). Our expansion of the Breslow mechanism
is as follows.
Formaldehyde (C1) alone is incapable of undergoing an aldol reaction, since it
lacks an acidic proton alpha to the carbonyl group. The two-carbon sugar glycolade-
hyde (C2) is the smallest such system with an active hydrogen, so Breslow hypoth-
esized it must be present in catalytic amounts. The product of the aldol condensation
