title: Synthesis of a new class of isothiocyanatopeptide bifunctional chelating agents for coupling to monoclonal antibodies.
abstract: The preparation of a new class of isothiocyanatopeptide bifunctional chelating agents, Boc-glycyl-L-(p-NCS)phenylalanylglycylglycine ethyl ester 1, N-(S-acetylmercaptoacetyl)-L-(p-NCS)phenylalanylglycylglycine ethyl ester 2, and N-(S-acetylmercaptoacetyl)glycyl-L-(p-NCS)phenylalanylglycine ethyl ester 3, starting from Boc-L-(p-nitro)phenylalanine 5 is described. The key intermediates, nitropeptides 7, 8 and 12, were prepared by standard DCC coupling and a deprotection procedure. The nitropeptides 7 and 12 on condensation with N-succinimidyl-S-acetylthioacetate provided a good yield of the corresponding S-(acetylmercaptoacetyl)nitropeptides 10 and 13, respectively. Catalytic hydrogenolysis of compounds 8, 10 and 13, followed by thiophosgenyation gave 28-95% yield of target products 1, 2 and 3, respectively. Compounds 1-3 were conjugated to the monoclonal antibody D612 reactive with human colon carcinoma using 12/1 to 60/1 ligand to antibody molar ratios, and the conjugates were labeled with 99mTc. The in vitro cell binding results of these immunoconjugates demonstrate that they retained their antibody binding specificity.
authors.affiliation: Department of Radiation Oncology, University of Alabama, Birmingham, USA.
authors.forename: S
authors.initials: S
authors.lastname: Ram
authors.forename: D J
authors.initials: DJ
authors.lastname: Buchsbaum
mesh_terms: D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000378:metabolism* / Q000494:pharmacology; D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000473:pathology; D004355:Drug Stability; D006801:Humans; D017879:Isothiocyanates / Q000138:chemical synthesis* / Q000737:chemistry; D007553:Isotope Labeling; D008545:Melanoma / Q000188:drug therapy / Q000276:immunology / Q000473:pathology; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D013667:Technetium; D014407:Tumor Cells, Cultured
chemical_list: D000911:Antibodies, Monoclonal; D002614:Chelating Agents; D017879:Isothiocyanates; D010455:Peptides; D013667:Technetium