F on: Fluorotriorganosilyl‐derivatized Tyr3‐octreotate was labeled with 18F− providing the first practical formulation in 18F‐radiochemistry for the labeling of a peptide (see scheme). The very mild reaction conditions and the fast labeling make this strategy a valuable tool for the synthesis of 18F‐radiopharmaceuticals.

The syntheses of different (18)F-labeled peptides using the highly effective labeling synthon p-(di- tert-butylfluorosilyl) benzaldehyde ([ (18)F]SiFA-A) for the development of (18)F-radiopharmaceuticals for oncological positron emission tomography (PET) is reported. The novel and mild labeling technique for the radiosynthesis of [ (18)F]SiFA-A, based on an unexpectedly efficient isotopic (19)F- (18)F exchange, yielded the (18)F-synthon [ (18)F]SiFA-A in almost quantitative yields in high specific activities between 225 and 680 GBq/micromol (6081-18 378 Ci/mmol) without applying HPLC purification. The [ (18)F]SiFA-A was finally used to label the N-terminal amino-oxy (N-AO) derivatized peptides AO-Tyr (3)-octreotate (AO-TATE), cyclo(fK(AO-N)RGD and N-AO-PEG 2-[D-Tyr-Gln-Trp-Ala-Val-betaAla-His-Thi-Nle-NH 2] (AO-BZH3, a bombesin derivative) in high radiochemical yields. Density functional theory (DFT) calculations confirmed high efficiency of the isotopic exchange, which is predicted to proceed via a pentacoordinate siliconate intermediate dissociating immediately to form the radiolabeled [ (18)F]SiFA-A.

The synthesis of the o-phenylene-bridged ditin species o-C 6 H 4 (SnXMe 2 ) 2 (2, X ) Cl; 4, X ) F) and o-C 6 H 4 (SnCl 2 Me) 2 (3) is reported and the crystal structures of [o-C 6 H 4 (SnClMe 2 ) 2 ‚ Cl] -[(Ph 3 N) 2 P] + (5) and [o-C 6 H 4 (SnClMe 2 ) 2 ‚F] -[K‚C 20 H 24 O 6 ] + (7) are described. Variabletemperature 119 Sn and 19 F NMR studies indicate that 2 and 4 act as bidentate Lewis acids toward chloride and fluoride ions exclusively forming the stable anionic 1:1 complexes 5, 7, and [o-C 6 H 4 (SnFMe 2 ) 2 ‚F] -[Et 4 N] + ( 8). No formation of dianionic 1:2 adducts was observed even with excess of halide ions. The affinity of 2 toward fluoride is greater than toward chloride. Reaction of 2 with HMPA gives the neutral complex o-C 6 H 4 (SnClMe 2 ) 2 ‚(Me 2 N) 3 PO (10), the crystal structure of which is also described.

The synthesis of the aryldiphosphonic ester C 6 H 2 [P(O)(OEt) 2 ] 2 -1,3-t-Bu-5 (2) and of its organotin derivatives Cand C 6 H 3 [P(O)(OEt) 2 ] 2 -2,4-(Ph 2 RSn) 2 -1,5 (10, R ) Ph; 11, R ) Br). X-ray investigations reveal weak intramolecular Sn-O interactions for 6 (2.865(3)-3.063(4) Å), 9 (2.803(3) Å), and 10 (2.793(2) Å) but strong Sn-O coordinations for 7 (2.203(5)/2.278(6) Å) and 11 (2.379(3)/ 2.412(3) Å), indicating the high donor capacity of the new rigid O,C,O-and O,C-chelating ligands in these compounds. NMR studies confirm that the basic coordination geometry found in the solid state is maintained in solution.