Linear-dichroic infrared spectra (IR-LD) of 3-ethoxy-4-(N-norcodeino-)cyclobutene-1,2-dione (1) and codeine dihydrogenphosphate (Codeinum phosphoricum) (2), oriented as solid suspensions in nematic liquid crystals, have been measured. IR characteristic band assignments were made, and used in stereo-structural predictions. The results were compared with crystallographic structures of similar organic systems, and found to be in good agreement.
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 H.J. Gruss, A. Sutton and P. Horton: “Codeine-induced slow transit in healthy volunteers and its alteration by peripheral opiate agonists”, Gastroenterology, Vol. 128, (2005), pp. A465–A466.
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