摘要:
A novel fluorine- 18-labeled O-6 -benzylguanine (O-6-BG) derivative, 0(6)-[4-(2-[F-18]fluoroetboxymethyl)benzyl[guanine (O-6-[F-18]FEMBG, [[F-18]1), has been synthesized for evaluation as a potential positron emission tomography (PET) probe for the DNA repair protein O-6-alkylguanine-DNA alkyltransferase (AGT) in cancer chemotherapy. The appropriate radiolabeling precursor N-2,(9)-bis(p-anisyldiphenylmethyl)-O-6-[4-(hydroxymethyl)benzyl]guanine (6) and reference standard O-6-[4-(2-fluoroethoxymethyl)benzyl]guanine (O-6 -FEMBG, 1) were synthesized from 1,4-benzenedimethanol and 2-amino-6-chloropurine in four or six steps, respectively, with moderate to excellent chemical yields. The target tracer O-6-[F-18]FEMBG was prepared in 20-35% radiochemical yields by reaction of MTr-protected precursor 6 with [F-18]fluoroethyl bromide followed by quick deprotection reaction and purification with a simplified Silica Sep-Pak method. Total synthesis time was 60-70 min from the end of bombardment. Radiochemical purity of the formulated product was >95%, with a specific radioactivity of >1.0 Ci/mu mol at the end of synthesis. The activity of unlabeled O-6-FEMBG was evaluated via an in vitro AGT oligonucleotide assay. Preliminary findings from biological assay indicate that the synthesized analogue has similarly strong inhibiting effect on AGT in comparison with O-6-BG and O-6-4-fluorobenzylguanine (O-6-FBG). The results warrant further in vivo evaluation of O-6-[F-18]FEMBG as a new potential PET probe for AGT. (c) 2005 Elsevier Ltd. All rights reserved.