FLUORO NORCHOLESTEROL ANALOGUES. SYNTHESIS OF 6β-(2'-FLUORO)ETHYL-19-NORCHOLEST-5(10)-EN-3β-OL

Article abstract of DOI:10.1016/0039-128X(82)90058-7

A synthetic route for labelling 6β-(2'-fluoro)ethyl-19-norcholest-5(10)-en-3β-ol (VII) with fluorine-18 was developed to evaluate the potential utility of VII as an adrenal imaging agent. 6β-p-Toluenesulphonyloxymethyl-19-norcholest-5(10)en-3β-ol acetate (I) was converted to the 6β-(2'-hydroxy)ethyl (VI) in a five-step process.The treatment of VI with N,N-diethyl(2-chloro-1,1,2-trifluoroethyl)amine in methylene chloride and subsequent hydrolysis with base gave the required VII.Iodination of VI with triphenoxymethylphosphonium iodide followed by alkaline hydrolysis gave the 6β-(2'-iodo)ethyl (IX) which, on treatment with silver fluo ride in acetonitrile, furnished the 6β-(2'-fluoro)ethyl (VII).Excellent conversion of the 6β-(2'-p-toluenesulphonyloxy)ethyl (X) into VII was also achieved by heating with potassium fluoride for 2 hr in ethylene glycol in 76percent yield, which is a readily applicable method for labelling with fluorine-18.