Tetraisopropyl methylenediphosphonate (I) was alkylated with 3-(acetylthio)propyl iodide (II) in the presence of NaH to give (III). Then, hydrolysis of both thioester and phosphonate esters of (III) with refluxing HCl provided the intermediate thiol (IV).

Selective acylation of the silyl ester of prostaglandin E2 (V) at C-15 hydroxyl group with bromoacetyl bromide in the presence of pyridine at -25 C afforded bromoacetate ester (VI). Then, displacement of the halogen atom with thiol (IV) in aqueous dioxan furnished the correspondig desilylated sulfide. This was finally converted into the title disodium phosphonate salt by treatment with cation exchange resin.

Tetraisopropyl methylenediphosphonate (I) was alkylated with 3-(acetylthio)propyl iodide (II) in the presence of NaH to give (III). Then, hydrolysis of both thioester and phosphonate esters of (III) with refluxing HCl provided the intermediate thiol (IV).

Selective acylation of the silyl ester of prostaglandin E2 (V) at C-15 hydroxyl group with bromoacetyl bromide in the presence of pyridine at -25 C afforded bromoacetate ester (VI). Then, displacement of the halogen atom with thiol (IV) in aqueous dioxan furnished the correspondig desilylated sulfide. This was finally converted into the title disodium phosphonate salt by treatment with cation exchange resin.