2,6-Pyridinedicarbothioic acid (PDTC) is an

organosulfur Organosulfur chemistry is the study of the properties and synthesis of organosulfur compounds, which are organic compounds that contain sulfur. They are often associated with foul odors, but many of the sweetest compounds known are organosulfur der ...

compound that is produced by some bacteria. It functions as a

siderophore Siderophores (Greek: "iron carrier") are small, high-affinity iron- chelating compounds that are secreted by microorganisms such as bacteria and fungi. They help the organism accumulate iron. Although a widening range of siderophore functions is n ...

, a low molecular weight compound that scavenges

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. Siderophores solubilize compounds by forming strong complexes. PDTC is secreted by the

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...

'' Pseudomonas stutzeri'' and ''

Pseudomonas putida ''Pseudomonas putida'' is a Gram-negative, rod-shaped, saprophytic soil bacterium. It has a versatile metabolism and is amenable to genetic manipulation, making it a common organism used in research, bioremediation, and synthesis of chemicals and ...

''.

Synthesis and biosynthesis

PDTC can be synthesized in the laboratory by treating the diacid dichloride of pyridine-2,6-dicarboxylic with H₂S in

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

: : This route produces the pyridinium salt of pyridinium-2,6-dicarbothioate. Treatment of this orange-colored salt with

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

gives colorless PDTC, which can then be extracted with

dichloromethane Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...

. The biosynthesis of PDTC remains unclear although some insights can be deduced from the genetics. It is suggested that ''Pseudomonas stutzeri'' may have acquired at least one of the genes by lateral transfer from

mycobacteria ''Mycobacterium'' is a genus of over 190 species in the phylum Actinomycetota, assigned its own family, Mycobacteriaceae. This genus includes pathogens known to cause serious diseases in mammals, including tuberculosis ('' M. tuberculosis'') a ...

. In a proposed biosynthetic sequence pyridine-2,6-dicarboxylic acid, a known bacterial metabolite, is activated as its bis-

adenosine monophosphate Adenosine monophosphate (AMP), also known as 5'-adenylic acid, is a nucleotide. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine. It is an ester of phosphoric acid and the nucleoside adenosine. As a substituent it t ...

(AMP) derivative. The sulfur donor and its activation remain uncertain.

Coordination chemistry

PDTC binds to both Fe²⁺ and Fe³⁺. The ferric complex is brown, whereas the ferrous complex is blue. In the presence of air, the ferrous complex oxidizes to the ferric compound.Ockels, W., Roemer, A., Budzikiewicz, H., Korth, H., Pulverer, G., "Bacterial constituents. II. An iron(II) complex of pyridine-2,6-di-(monothiocarboxylic acid) - a novel bacterial metabolic product", Tetrahedron Lett. 1978, 3341. It is iron selective as only the Fe complex is soluble in water. PDTC is produced mainly during the exponential phase of bacterial growth. The conditions at which ''Pseudomonas'' produces PDTC is 25 °C, pH=8 and sufficient aeration.

References

{{DEFAULTSORT:Pyridinedicarbothioic acid, 2,6- Thiocarboxylic acids Disubstituted pyridines

Synthesis and biosynthesis

Coordination chemistry

See also

References