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Synthesis of aldehydic ribonucleotide and amino acid precursors by photoredox chemistry.

Ritson DJ, Sutherland JD - Angew. Chem. Int. Ed. Engl. (2013)

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Affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.

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In continuing studies aimed at understanding the prebiotic origin of RNA, we recently demonstrated a Kiliani–Fischer-type synthesis of simple sugars from hydrogen cyanide using photoredox cycling of cyanocuprates (Scheme 1)... The photoredox cycle oxidizes to cyanogen and generates associated reducing power in the form of protons and hydrated electrons, which reduce further to formaldehyde imine... Although our previous Kiliani–Fischer-type synthesis started with hydrogen cyanide and proceeded through glycolonitrile, compound itself is probably a more plausible starting point for the synthesis... In the absence of added ammonia, cyanohydrins and produced by rain-in of hydrogen cyanide into the system have the potential to be further reduced in a second stage of photoredox chemistry (Scheme 2)... If the first-stage reduction were to proceed to completion, all of the glycolaldehyde needed to make ribonucleotides and serine (via and ) would instead be converted into acetaldehyde... We found that was the major product after 6 h irradiation thus 2–4 h would seem to be synthetically most productive from a systems perspective... Not knowing the UV light intensity on the early earth means that we cannot convert our experimental irradiation times into real time spans, but diurnal cycling and/or weather effects mean that illumination periods corresponding to 2–4 of our hours are plausible... Addition of hydrogen cyanide is needed to make cyanohydrins for the second-stage reduction as well as for aminonitrile synthesis... Thus the abiogenesis of the simple sugars required to make RNA appears to be closely related to the abiogenesis of at least four of the proteinogenic amino acids of extant biology... The reductant hydrogen sulfide and the copper(I) cyanide based catalyst could be produced by dissolution of a copper sulfide mineral in cyanide solution, additional being produced by similar dissolution of ferrous sulfide... At this stage we do not attempt to describe a more detailed scenario other than to point out that the RNA and amino acid syntheses could take place in one mixed system or in several closely related systems which then become mixed... Finally, we note that the chemistry we describe, utilizing the reducing power of hydrogen sulfide to generate multiple (proto)biomolecules ultimately from C1 feedstock(s), is reminiscent of the general scenario put forward by Wächtershäuser.

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13C NMR spectrum of the products of irradiation (2 h, pH 7) of a system made by mixing a solution of [13C2]-labeled glycolonitrile 5 (10 mm), hydrogen sulfide 10 (30 mm), and sodium phosphate (33 mm) with solid copper(I) cyanide (10 mol % with respect to 5).
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fig02: 13C NMR spectrum of the products of irradiation (2 h, pH 7) of a system made by mixing a solution of [13C2]-labeled glycolonitrile 5 (10 mm), hydrogen sulfide 10 (30 mm), and sodium phosphate (33 mm) with solid copper(I) cyanide (10 mol % with respect to 5).


Synthesis of aldehydic ribonucleotide and amino acid precursors by photoredox chemistry.

Ritson DJ, Sutherland JD - Angew. Chem. Int. Ed. Engl. (2013)

13C NMR spectrum of the products of irradiation (2 h, pH 7) of a system made by mixing a solution of [13C2]-labeled glycolonitrile 5 (10 mm), hydrogen sulfide 10 (30 mm), and sodium phosphate (33 mm) with solid copper(I) cyanide (10 mol % with respect to 5).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4269183&req=5

fig02: 13C NMR spectrum of the products of irradiation (2 h, pH 7) of a system made by mixing a solution of [13C2]-labeled glycolonitrile 5 (10 mm), hydrogen sulfide 10 (30 mm), and sodium phosphate (33 mm) with solid copper(I) cyanide (10 mol % with respect to 5).

View Article: PubMed Central - PubMed

Affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

In continuing studies aimed at understanding the prebiotic origin of RNA, we recently demonstrated a Kiliani–Fischer-type synthesis of simple sugars from hydrogen cyanide using photoredox cycling of cyanocuprates (Scheme 1)... The photoredox cycle oxidizes to cyanogen and generates associated reducing power in the form of protons and hydrated electrons, which reduce further to formaldehyde imine... Although our previous Kiliani–Fischer-type synthesis started with hydrogen cyanide and proceeded through glycolonitrile, compound itself is probably a more plausible starting point for the synthesis... In the absence of added ammonia, cyanohydrins and produced by rain-in of hydrogen cyanide into the system have the potential to be further reduced in a second stage of photoredox chemistry (Scheme 2)... If the first-stage reduction were to proceed to completion, all of the glycolaldehyde needed to make ribonucleotides and serine (via and ) would instead be converted into acetaldehyde... We found that was the major product after 6 h irradiation thus 2–4 h would seem to be synthetically most productive from a systems perspective... Not knowing the UV light intensity on the early earth means that we cannot convert our experimental irradiation times into real time spans, but diurnal cycling and/or weather effects mean that illumination periods corresponding to 2–4 of our hours are plausible... Addition of hydrogen cyanide is needed to make cyanohydrins for the second-stage reduction as well as for aminonitrile synthesis... Thus the abiogenesis of the simple sugars required to make RNA appears to be closely related to the abiogenesis of at least four of the proteinogenic amino acids of extant biology... The reductant hydrogen sulfide and the copper(I) cyanide based catalyst could be produced by dissolution of a copper sulfide mineral in cyanide solution, additional being produced by similar dissolution of ferrous sulfide... At this stage we do not attempt to describe a more detailed scenario other than to point out that the RNA and amino acid syntheses could take place in one mixed system or in several closely related systems which then become mixed... Finally, we note that the chemistry we describe, utilizing the reducing power of hydrogen sulfide to generate multiple (proto)biomolecules ultimately from C1 feedstock(s), is reminiscent of the general scenario put forward by Wächtershäuser.

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