Prebiotic sugar synthesis: Hexose and hydroxy acid synthesis from glyceraldehyde catalyzed by iron(III) hydroxide oxide

Abstract

Iron(III) hydroxide oxide [Fe(OH)O] efficiently catalyzed the condensation of 25 mM DL-glyceraldehyde to ketohexoses at 25 degrees C (pH 5-6). At 16 days the yields were sorbose (15.2%), fructose (12.9%), psicose (6.1%), tagatose (5.6%), and dendroketose (2.5%) with 19.6% of triose unreacted. Analysis at 96 days showed no decomposition of hexoses. Under these conditions Fe(OH)O also catalyzed the isomerization and rearrangement of glyceraldehyde to dihydroxyacetone and lactic acid, respectively. In these reactions, about 10% of the glyceraldehyde was oxidized to glyceric acid with concurrent reduction of the iron(III) to iron(II). The partial reduction of Fe(OH)O did not noticeably reduce its ability to catalyze hexose synthesis. The relationship of these results to prebiotic sugar synthesis is discussed.

The Astrobiology Primer v2.0

“…This simplest aldehyde can be formed under a variety of conditions, including UV irradiation of the primordial atmosphere composed of H 2 O, CO 2 , and H 2 (Pinto et al , 1980) or even simply H 2 O and CO 2 (Bar-Nun and Hartman, 1978); electric discharge, possible in a wide range of atmospheric compositions based on CH 4 , H 2 , H 2 O, N 2 , and CO or CO 2 (Miller and Schlesinger, 1984); or photoreduction reactions (Chittenden and Schwartz, 1981). Various other aldehydes and sugars can be synthesized by condensation of formaldehyde (Weber, 1992) or by direct synthesis pathways similar to those of formaldehyde formation. Formaldehyde is also a substrate in the formose-type reactions—the sugar polymerization—which has been proposed as a historically first prebiotic route to obtain various mixtures of sugars (Breslow, 1959; Fig.…”

Bis[( l )prolinate-N,O]Zn: A water-soluble and recycle catalyst for various organic transformations

“…Previously, the self condensation of formaldehyde in basic medium was used to synthesize pentoses to yield less than 1% of riboses [63]. So the investigations were carried out to escalate the amount and stability of pentoses.…”

Sugar-Driven Prebiotic Synthesis of Ammonia from Nitrite

“…As shown in Pathway-A2, the 3-deoxy-aldos-2-ulose products of sugar β-dehydration can hydrate and ionize to give α-ketoaldehyde aldehydrol anion intermediate (structure III) that either alone, or complexed to Fe +3 as the monoanion (structure IV) or C2-hydrate dianion (not depicted) drives the reduction of nitrite to ammonia. It is possible that Fe +2 instead of Fe +3 is involved in catalysis, because glyceraldehyde has been shown to reduce Fe +3 in iron(III) oxide hydroxide to Fe +2 under similar conditions (Weber 1992). However, it is unlikely that Fe +2 directly reduces nitrite to ammonia in the pH 4.5-5.5 reactions described here, because other studies have shown that nitrite reduction to ammonia by Fe +2 requires a pH≥7 (Summers and Chang 1993).…”

“…These pathways are consistent with (1) the known sugar transformations of isomerization, enolization, and β-dehydration (Speck 1958;Feather and Harris 1973), (2) the results here showing that only molecules containing an α-hydroxyaldehyde, α-hydroxyketone, or α-ketoaldehyde group capable of forming enediolate and aldehydrol anion intermediates are able to reduce nitrite to ammonia, (3) the established involvement of the anionic form of aldehyde hydrates (anhydrols) in hydride transfer (Fratzke and Reilly 1986;Watt 1988), and (4) studies showing that aldonic acids are the major product of sugar oxidation by iron(III) oxide hydroxide and several other oxidants (Green 1980;Weber 1992). As shown, the pathways begin by the reversible isomerization of aldoses yielding their respective ketoses, followed by β-dehydration to give their respective 3-deoxy-aldos-2-uloses (e.g.…”