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Iron-sulfur clusters are ancient cofactors that play a fundamental role in metabolism and may have impacted the prebiotic chemistry that led to life. However, it is unclear whether iron-sulfur clusters could have been synthesized on prebiotic Earth. Dissolved iron on early Earth was predominantly in the reduced ferrous state, but ferrous ions alone cannot form polynuclear iron-sulfur clusters. Similarly, free sulfide may not have been readily available. Here we show that UV light drives the synthesis of [2Fe-2S] and [4Fe-4S] clusters through the photooxidation of ferrous ions and the photolysis of organic thiols. Iron-sulfur clusters coordinate to and are stabilized by a wide range of cysteine-containing peptides and the assembly of iron-sulfur cluster-peptide complexes can take place within model protocells in a process that parallels extant pathways. Our experiments suggest that iron-sulfur clusters may have formed easily on early Earth, facilitating the emergence of an iron-sulfur-cluster-dependent metabolism.

Visible-light-induced specific desulfurization of cysteinyl peptides has been explored. The photocatalytic desulfurization catalyzed by Ru(bpy)32+ can proceed efficiently at room temperature in aqueous solution or in binary mixtures of aqueous/organic solvent and be compatible with the presence of residues of amino acids, carbohydrates, and various sulfur-containing functional groups. This approach was successfully applied to synthesize linear and cyclic peptides through the ligation-desulfurization protocol.

A visible-light-induced metal-free desulfurization method for thiols and disulfides has been explored. This radical desulfurization features mild conditions, robustness, and excellent functionality compatibility. It was successfully applied not only to the desulfurization of small molecules, but also to peptides.

The invention relates to a desulfurization method of organic compounds, in particular, organic compounds containing mercapto or a disulfide bond. The method comprises following steps: dissolving organic compounds containing mercapto or a disulfide bond by a solvent; adding a phosphine reagent and an initiator; and carrying out reactions in the presence of light to convert the substrate into corresponding desulfurization products. The organic compounds containing mercapto or a disulfide bond is R-SH or R-S-S-R; wherein R represents a primary carbon group, a secondary carbon group, a tertiary carbon group, an aryl group, or an acyl group. The reactions do not need any metal, and the reaction conditions are mild. Moreover, the desulfurization method has the advantages of high yield, wide substrate application range, and multiple suitable solvents, and is widely suitable for multiple kinds of mercapto-removing reactions and desulfurization reactions of disulfide.

A scalable protocol for the desulfurization of cysteine by using visible light, the photocatalyst Ir(dF(CF3)ppy)2(dtb-bpy)PF6 and triethylphosphite under biphasic reaction conditions has been developed. The loading of the catalyst can be as low as 0.01?mol%, which can be efficiently removed during the workup (≤0.3?ppm), giving rise to the corresponding desulfurized product in high yields. This method has been applied also to cystine, penicillamine, and reduced and oxidized glutathione. The desulfurization has been found to be pH sensitive, with an optimal pH value of 6.5 and 7.0 for the cysteine derivatives and glutathione, respectively. In addition, during the desulfurization of a decapeptide containing cysteine and methionine, concurrent oxidation of the two sulfur-containing residues to disulfide and sulfoxide has been observed. Therefore, whereas the presented protocol allows a straightforward visible light-mediated desulfurization of simple thiols by using very low catalyst loading and a cost-effective trialkylphosphite as thiyl radical trapping agent, its application to complex substrates needs to be carefully validated. Copyright

A visible light-induced desulfurization process for thiols and disulfides using triethylphosphite and triethylborane is reported. The reaction can be effected on a range of organic molecules having either primary, secondary or tertiary thiol groups and disulfides without the need of protecting groups. Thus, after treating L-cystine 7, L-cystine dimethylester 8, thioctic amide 9 and glutathione disulfide 10, first with tributylphosphine, later with triethylborane/triethylphosphite under irradiation in a one-pot reaction, the corresponding desulfurized compounds L-Ala, L-Ala, 1-octanamide and γ-L-Glu-L-Ala-Gly, respectively, are prepared in high yields with retention of configuration.

Thiol groups can be reductively eliminated at room temperature by a photochemical method which makes use of triethylboron, triethylphosphite and visible light. Thus, after treating L-Cys 1a, D-Pen 1b, L-Cys-OMe 1c and glutathione (γ-L-Glu-L-Cys-Gly) 3, the corresponding desulfurized compounds L-Ala 2a, D-Val 2b, L-Ala-OMe 2c and γ-L-Glu-L-Ala-Gly 4, respectively, are prepared in high yields and with retention of configuration.

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