Organothiophosphate

Organothiophosphates or organophosphorothioates are a subclass of organophosphorus compounds and of thiophosphate compounds. They are the organic compounds that contain a phosphate group in which one or more oxygen atoms is substituted by sulfur. Many are used as pesticides, some have medical applications, and some are used as oil additives.^[1] They generally have the chemical formula (RO)₃PS, [(RO)₂P(S)O]⁻, R(RO)₂PS, etc.

Oligonucleotide phosphorothioates (OPS) are modified oligonucleotides where one of the oxygen atoms in the phosphate moiety is replaced by sulfur. These compounds are the basis of antisense therapy, e.g., the drugs fomivirsen (Vitravene), Oblimersen, Alicaforsen, and Mipomersen (Kynamro).^[2]

Further examples of these include:

• Diazinon
• Fenitrothion
• Fenthion
• Thiotepa

Variants with P=S double bonds were developed as insecticides because of their reduced mammalian toxicity. The phosphorothioate P=S bond is converted to the toxic P=O bond in the target insect. Similar oxidative conversion in mammals is slower, conferring lower toxicity in mammals.