Synthesis of 2‐[(2‐chloro‐2′‐[ 18 F]fluoroethyl)amino]‐2H‐1,3,2‐oxazaphosphorinane‐2‐oxide ( 18 F‐fluorocyclophosphamide), a potential tracer for breast tumor prognostic imaging with PET

A fluorine‐18 labeled analog of the widely used chemotherapeutic agent cyclophosphamide was synthesized as a tracer for prognostic imaging with positron emission tomography. 2‐[(2‐Chloro‐2′‐[ 18 F]fluoroethyl)amino]‐2H‐1,3,2‐oxazaphosphorinane‐2‐oxide ( 18 F‐fluorocyclophosphamide), was prepared by direct halogen exchange reaction from the parent cyclophosphamide. In small‐scale syntheses, radiochemical yields of up to 4.9% and specific activities of 960 Ci/mmol were achieved in a total synthesis time of 60–75 min. The [ 18 F]‐labeled cyclophosphamide analog with radioactive purity >99% and chemical purity >96% was suitable for in vivo (microPET imaging) and ex vivo studies of a murine model of human breast tumors. Copyright © 2005 John Wiley & Sons, Ltd.