Determination of homonuclear scalar coupling constants by combining selective two-dimensional NMR spectroscopy with convolution and deconvolution: Applications to paclitaxel (taxol)

Homonuclear proton-proton coupling constants can be determined accurately by recording selective two-dimensional correlation spectra and by analyzing the resulting multiplets by two-dimensional convolution and deconvolution methods, In this work, these methods were evaluated by attempting to determine the complete set of homonuclear couplings in paclitaxel (taxol). Convolution methods have been applied successfully to ten pairs of complementary multiplets recorded by selective correlation spectroscopy (soft-COSY) and pure in-phase correlation spectroscopy (PICSY). These pairs of multiplets gave reliable measurements of ten active couplings, In some cases, satisfactory PICSY spectra could not be obtained, so that the complementary information of soft-COSY and PICSY could not be exploited, Furthermore, couplings involving two strongly-coupled diastereotopic protons (14H(alpha) and 14H(beta)) could not be determined in a satisfactory manner. Further problems arose due to partial overlap of the chemical shifts of two other protons (10H and 13H). Deconvolution has been applied successfully to all 14 soft-COSY multiplets, yielding 14 estimates of active couplings and 38 estimates of passive splittings. This work provides between one and seven estimates for 21 coupling constants, The accuracy of these different estimates must be weighed with the complexity of the methods used, This work may help to assess the perspectives of completely automated computer-supported analysis of two-dimensional spectre. (C) 1997 by John Wiley & Sons, Ltd.