Microwave-enhanced nucleophilic fluorination in the synthesis of fluoropyridyl derivatives of [3,2-c]pyrazolo-corticosteroids, potential glucocorticoid receptor-mediated imaging agents.

Fluoropyridyl derivatives of [3,2-c]pyrazolo-corticosteroids have high affinity for the glucocorticoid receptor (GR) and are highly active glucocorticoids. They are thus considered to be excellent candidates for PET imaging of GR containing tissues when labeled with fluorine-18 (t(1/2)=110 min). Previously reported syntheses of these fluorinated glucocorticoids were accomplished by conventional thermal nucleophilic halogen exchange reactions with chloropyridyl precursors.