New synthesis system of (C‐11)propyl ketene and its reactons with various alcohols

A new synthesis of (C-11)propyl ketene using a HCl/Helium gas mixture and glass beads was developed. This improved synthesis method gave high yields and good reproducibility, which had been difficult to attain with our previous method. The (C-11) propyl ketene is a useful precursor for labeling, in high specific activity, bioactive compounds which have a hydroxyl group. The reactivity of (C-11) propyl ketene in the acylation of various alcohols was evaluated. The relative reactivity of primary, secondary and tertiary alcohols were 1, 0.4 and 0.1, respectively, and the reactivity of the noncarrier added conditions was similar to that using cold propyl ketene. This (C-11)propyl ketene was also useful for the formation of N-butyl compounds, making it possible to label many bioactive compounds.