Cocaine gold chloride complex

The structure of the cocaine gold chloride coordination complex has been studied and found to be a salt type complex of the type ($\rm C\sb{17}H\sb{21}NO\sb4H\sp+$) (AuCl$\sb4\sp-$). The structure elucidation was accomplished via U.V., I.R., $\sp1$H and $\sp{13}$C NMR spectroscopy as well as by chemical methods such as qualitative and quantitative analysis and the synthesis of structural analogs. Chemical shifts and coupling constants ($\sp1$H and $\sp{13}$C) results on the gold salt complex confirmed several published assignments and the conformation in cocaine. Nuclear Overhauser Enhancement Difference Spectra (NOEDS) allowed unequivocal assignment of certain unpublished signals, H-6,7$\sb{\rm endo}$ and H-6,7$\sb{\rm exo}$ in cocaine. NOEDS also established the chair conformation of the tropane ring and equatorial N-methyl orientation in the cocaine gold chloride salt complex with small deformations in the tropane moiety. Unique intramolecular hydrogen bonding, between the protonated 8-aza nitrogen and the O-ester at C-2, in solvents which will not on the time scale of the NMR support intermolecular hydrogen bonding, results in unusual deshielding of the H-4$\sb{\rm ax}$ resonance in cocaine salts. Finally, proton spin-lattice relaxation times (T$\sb{\rm 1}$'s) demonstrated the complex was indeed a true salt and the 3$\sp\circ$ nitrogen is not a tightly complexed ligand. As a result of the present work, the nature of cocaine-gold chloride complex, which has been used in microcrystalline microscopic analytical techniques of forensic drug analysis for over 70 years, has for the first time been determined.