Radioiodinations of organic molecules on silica gel surfaces

Synthesis of the Side Chain Cross-Linked Tyrosine Oligomers Dityrosine, Trityrosine, and Pulcherosine

[reaction: see text] An efficient synthesis of dityrosine and the first syntheses of the tyrosine trimers trityrosine and pulcherosine have been achieved. Protected 3-iodotyrosine underwent tandem Miyaura borylation-Suzuki coupling to give protected dityrosine. The choice of benzyl carbamate, ester, and ether protecting groups enabled a one-step global deprotection to give dityrosine. Suzuki coupling of protected 3,5-diiodotyrosine and tyrosine-3-boronic acid derivatives gave the corresponding trityrosine, but in low yield. However, use of a potassium tyrosine-3-trifluoroborate derivative in place of the corresponding pinacol boronate ester, in combination with protecting group variation, gave protected trityrosine in good yield. Access to pulcherosine was achieved through copper-catalyzed coupling of phenylalanine-4-boronic acid and 4-O-protected dopa derivatives to give an isodityrosine derivative. Selective halogenation followed by Suzuki coupling with the potassium tyrosine-3-trifluoroborate gave protected pulcherosine. Global deprotection of the protected trityrosine and pulcherosine derivatives completed the first syntheses of the corresponding tris-alpha-amino acids.

Recent study on radioiodination of [4-127I]iodoantipyrine via isotope-exchange in dry-states up-to melt

A recent study on the radioiodination of [4-127I]iodoantipyrine with Na131I via no-carrier-added isotope exchange in dry-states up-to melt at 160 degrees C using different inorganic ammonium salts as catalyst was described at different reaction conditions of concentrations and temperatures (100-160 degrees C). A radiochemical yield (%) up to 98.5 of pure [4-131I]iodoantipyrine was obtained in melt (at 160 degrees C) using di-ammonium hydrogen orthophosphate within 2-5 min. The reaction offers a good possibility to label [4-127I]iodoantipyrine with short-lived radioiodine isotopes with no substrate decomposition.

Technical challenges associated with the radiolabeling of monoclonal antibodies utilizing short-lived, positron emitting radionuclides

Many factors, both physical and chemical, affect the radiolabeling of a chemical compound. These factors add a new dimension of complexity when the labeling of monoclonal antibodies is attempted with short-lived, positron emitting radionuclides. A lack of appreciation for the unique chemical separations associated with the radionuclide incorporated into the synthetic precursor can often lead to unexpected or non-reproducible results.