Syntheses, Spectroscopic Properties, Crystal Structures, and Antitumor Activities of the Optically Isomeric Mandelate Chelates, Mandelato(trans-1,2-diaminocyclohexane)platinum(II)

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Abstract
The four optical isomers of mandelato(trans-1,2,-diaminocyclohexane)platinum(II) have been prepared. The CD and NMR spectra of these compounds in solution indicate that the mandelate coordinates to platinum(II) to form a five-membered chelate ring. The X-ray crystal structure analyses of a pair of diastereomers, (R)-mandelato[(1R,2R)-1,2-diaminocyclohexane]platinum(II) and (S)-mandelato[(1R,2R)-1,2-diaminocyclohexane]platinum(II), have confirmed that the skeletal configuration of (R)- or (S)-mandelic acid is retained during the chelation of platinum(II). As a whole, the structural features of both diastereoisomers are analogous to each other. However, slight differences in hydrogen bonding are noticeable in relation to the solubilities. A preliminary animal test against mice leukemia L1210 was carried out using these compounds. The four isomers show different activities. All these facts together support the conclusion that the chiralities of both ammine (carrier) and mandelate (leaving group) influence the antitumor activities of the platinum agents.