Table of Contents
Metal-Based Drugs
Volume 1 (1994), Issue 1, Pages 31-39
http://dx.doi.org/10.1155/MBD.1994.31

Synthesis of the Sulphonate and Phosphonate Derivatives of Mercaptoacetyltriglycine. X-Ray Crystal Structure of Na2[ReO(Mercaptoacetylglycylglycylaminomethanesulphonate)]·3H2O

Departments of Chemistry and Radiology, Emory University, Atlanta 30322, Georgia, USA

Received 28 June 1993; Accepted 5 July 1993

Copyright © 1994 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Mercaptoacetyltriglycine forms complexes with R186/188e and T99mc radionuclides that are useful in nuclear medicine because they are substrates of the renal anion transport system. However, the renal clearance of [MO(MAG3)]2- (MAG3 = penta-anionic form of mercaptoacetyltriglycine, M = Re, Tc) complexes are less than ideal. Organic sulphonates are also transported by the renal anion transport system and phosphonates are similar to sulphonates in size and shape. In an effort to develop new ligands that form Re and Tc complexes and have improved renal clearances compared to [MO(MAG3)]2- complexes, the sulphonate and phosphonate derivatives of mercaptoacetyltriglycine were synthesized. The dianion [ReO(MAG2-AMS)]2- (MAG2-AMS = penta-anionic form of mercaptoacetylglycylglycylaminomethanesulphonic acid) was prepared for characterization by exchange reaction of ReOCl3(Me2S)(OPPh3) and isolated as the disodium salt. The structure of Na2[ReO(MAG2-AMS)]·3H2O (6) was determined by X-ray diffraction. The coordination geometry is pseudo square pyramidal, with the nitrogen and sulfur donor atoms forming a square base and the oxo ligand at the apex. The deprotonated sulphonate group has a syn conformation with respect to the oxo ligand. The renal clearances of [T99mcO(MAG2-AMS)]2- and [T99mcO(MAG2-AMP)]3- were similar in rats and suggest that the difference in total charge between the SO3- and PO32- groups is not important to renal clearance. However, their renal clearances were 40-50% less than that of [T99mcO(MAG3)]2- suggesting that the size and shape of the large tetrahedral SO3- and PO32- groups of [T99mcO(MAG2-AMS)]2- and [T99mcO(MAG2-AMP)]3- inhibit recognition by the renal transport system compared to the small planar CO2- group of [T99mcO(MAG3)]2-.