Studies on the lead-catalyzed synthesis of aldopentoses

The object of this work was to find an efficient means of synthesizing ribose in a manner that could be considered prebiotic. The starting point for synthesis was an aqueous solution of formaldehyde. Heretofore the most frequently used catalyst for this purpose has been calcium hydroxide. Unfortunately this system produces a wide array of products in addition to ribose which constitutes 1% or less of the final product. Attempts were made to find more mild conditions under which the formaldehyde could be reacted. Magnesium hydroxide suspensions were used for this purpose. Formaldehyde does not yield any sugars when incubated in magnesium hydroxide suspensions alone. However, if the magnesium hydroxide suspension was supplemented with doubly charged lead salts and catalytic amounts of any intermediate in the prebiotic pentose pathway, aldopentoses accounted for 30 per cent or more of the final product. The presence of lead in the incubation mixture also accelerated a number of other reactions including the interconversion of the four common aldopentoses, ribose, arabinose, lyxose and xylose.