Prebiotic Synthesis of Glycolaldehyde and Glyceraldehyde from Formaldehyde: A Computational Study on the Initial Steps of the Formose Reaction

In this work, the initial steps of the mechanism of the Formose reaction (FR) is computationally studied using DFT methods. The FR has been considered to be a relevant process in the prebiotic evolution leading to several types of sugars or carbohydrates. These molecules are some of the basic building blocks of the life. The dimerization of formaldehyde was found to take place via an intramolecular deprotonation reaction, leading to the formation of an intermediate which, after an isomerization, forms a Ca-complex of the cis-enediol tautomer of glycolaldehyde. The aldol reaction of this complex with additional formaldehyde gave glyceraldehyde, the simplest aldotriose. The catalyst Ca(OH)2 plays a dual role in the reaction, acting as a base (in the intramolecular deprotonation) and as Lewis acid (activating the carbonyl group) in the aldol addition.

Cometary Glycolaldehyde as a Source of pre-RNA Molecules

Over 200 molecules have been detected in multiple extraterrestrial environments, including glycolaldehyde (C₂(H₂O)₂, GLA), a two-carbon sugar precursor that has been detected in regions of the interstellar medium. Its recent in situ detection on the nucleus of comet 67P/Churyumov-Gerasimenko and through remote observations in the comae of others provides tantalizing evidence that it is common on most (if not all) comets. Impact experiments conducted at the Experimental Impact Laboratory at NASA's Johnson Space Center have shown that samples of GLA and GLA mixed with montmorillonite clays can survive impact delivery in the pressure range of 4.5 to 25 GPa. Extrapolated to amounts of GLA observed on individual comets and assuming a monotonic impact rate in the first billion years of Solar System history, these experimental results show that up to 10²³ kg of cometary GLA could have survived impact delivery, with substantial amounts of threose, erythrose, glycolic acid, and ethylene glycol also produced or delivered. Importantly, independent of the profile of the impact flux in the early Solar System, comet delivery of GLA would have provided (and may continue to provide) a reservoir of starting material for the formose reaction (to form ribose) and the Strecker reaction (to form amino acids). Thus, comets may have been important delivery vehicles for starting molecules necessary for life as we know it.

Mechanistic studies on the cascade conversion of 1,3-dihydroxyacetone and formaldehyde into α-hydroxy-γ-butyrolactone

The chemical synthesis of commercially and industrially important products from biomass-derived sugars is absolutely vital to establish biomass utilization as a sustainable alternative source of chemical starting materials. α-Hydroxy-γ-butyrolactone is a useful synthetic intermediate in pharmaceutical chemistry, and so novel biomass-related routes for its production may help to validate this eco-friendly methodology. Herein, we report the specific catalytic activity of homogeneous tin halides to convert the biomass-derived triose sugar 1,3-dihydroxyacetone and formaldehyde into α-hydroxy-γ-butyrolactone. A detailed screening of catalysts showed the suitability of tin catalysts for this reaction system, and isotope experiments using [D2]paraformaldehyde, substrate screening, and time profile measurements allowed us to propose a detailed reaction pathway. In addition, to elucidate the activated species in this cascade reaction, the effect of additional water and the influence of additional Brønsted acids on the reaction preferences for the formation of α-hydroxy-γ-butyrolactone, lactic acid, and vinyl glycolate were investigated. The active form of the Sn catalyst was investigated by (119)Sn NMR spectroscopy.

Unusual hydroxyl migration in the fragmentation of β-alanine dication in the gas phase

Experimental and theoretical investigations show that hydroxyl migration leads to unexpected fragmentation dynamics of β-alanine dication in the gas phase.