Isolation and characterization of major diterpenes from C. canephora roasted coffee oil

A simple laboratory procedure for the isolation of pure cafestol and 16-O-methylcafestol together with β-sitosterol from coffee is disclosed. Cafestol and 16-O-methylcafestol have been exhaustively characterized through 1D and 2D 1H, 13C NMR, CD and X-ray diffraction. For the first time, the molecular structure of cafestol is reported and the assignment of the absolute configuration is unequivocally given by exploiting anomalous scattering of a brominated derivative.

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CafestolC20H28O3Ee = n.d.[α]D20 = −119 (c 0.06, CH3OH)Source of chirality: natural sourceAbsolute configuration: (5S,8S,9R,10S,13R,16R)

16-O-MethylcafestolC21H30O3Ee = n.d.[α]D20 = −102 (c 0.13, CH3OH)Source of chirality: natural sourceAbsolute configuration: (5S,8S,9R,10S,13R,16R)

p-Bromobenzoyl ester of cafestolC27H31BrO4Ee = n.d.[α]D20 = −84.0 (c 0.13, CHCl3)Source of chirality: natural sourceAbsolute configuration: (5S,8S,9R,10S,13R,16R)