DACH Ligand

Each of the three isomeric forms of the dach ligand, fran.s-(R, R)-dach, frans-(S, S)-dach, and cis-dach, gives a platinum-ascorbate chelate that has unique physical properties. A detailed procedure is given here only for the synthesis of [Pt(trans-(R,R)-dach)(ascorbato-C, 0 )]-3H20. With minor variations, the same method is used in the syntheses of the platinum-ascorbate complexes of trans-(S, 5)-dach and c/s-dach. 

The reaction of [Pt(cis-dach)(H20)2] with sodium ascorbate gives a white precipitate that contains two isomeric forms of the [Pt(cis-dach)-(ascorbato-C, 0 )] chelate (due to a lack of rotational symmetry in the cis-dach ligand). The two isomers have different HPLC retention times and solubility properties, and may be separated by using the following method. 

The synthesis and antitumour properties of DACH platinum(II) complexes containing a variety of different types of leaving ligand have been reported [38, 39, 60-67]. Although early studies with the compounds were content to utilize mixtures of geometric and optical isomers, the realization that the stereochemistry of the DACH ligand influenced antitumour activity underscored the importance of working with isomerically pure forms of the diamine [68-70],... 

Basch et al. [44] used pseudopotential HF calculations for a determination of dissociation energies for the Pt-ligand bonds in cfv-[Pt(OCH3-0)(CH20H-C)(NH3)2]. This hypothetical compound models the antitumor-active complexes cis- [Pt(ascorbate)Cdach)] (dach = cyclohexane- 1,2-di-... 

Ligand mode assignments have been proposed from the IR spectra of Pt(dach)(L), where dach = irans-( ) 1,2-diaminocyclohexane, H2L = -substituted L-glutaric or L-aspartic acids.517 Similar data were given for [Pt4 (p2-isonic)4(dppf)4]4+, where isonic = isonicotinate, dppf = l,l -bis (diphenylphosphine)ferrocene.518 The IR spectrum of (83) includes vCOO of the P.O-ligand at 1638 cm-1.519... 

As was earlier outlined, a fi-hydroxo-bridged dimer (3) and trimer (4) can be synthesized via oligomerization of the aquo-hydroxo form of (1) (Scheme 4.2). Although a variety of complexes of this type have been reported [151-153], only those having cis ammonia ligands and the racemic form of 1,2-diaminocyclohexane (DACH) have been analyzed via X-ray structural analysis [13-16, 154, 155]. Structurally, the dimers are planar complexes containing a... 

This distinct oxaliplatin conformation is believed to result from the steric impact of the (R,R)-DACH carrier, which orients the hydrogen atoms on the ammine ligands such that the c/s-NHa can form a hydrogen bond... 

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