Direct evidence by carbon-13 NMR spectroscopy for the erythro configuration of the sphingoid moiety in Gaucher cerebroside and other natural sphingolipids.

By comparison of carbon-13 NMR data from Gaucher cerebroside and from other natural sphingolipids with those from synthetic L-threo-ceramide, D-glucosyl-L-threo-ceramide, D-erythro-ceramide and D-glucosyl-D-erythro-ceramide, we have been able to obtain directly, for the first time, unequivocal evidence for the erythro configuration of the sphingosine moiety in natural sphingolipids. Gaucher cerebroside gave the same data as D-glucosyl-D-erythro-ceramide. In contrast, significant shift differences have been observed for sphingosine C-3 (1.9 ppm) and C-4 (1.2 ppm) when comparing the spectral data of Gaucher cerebroside with those of D-glucosyl-L-threo-ceramide. Similar differences have also been found between the carbon-13 NMR data of synthetic D-erythro-ceramide and those of L-threo-ceramide. In addition, we have observed that threo-sphingosine C-5 and C-4 of ceramide and D-glucosyl-ceramide resonate near 129.5 ppm and 133.5 ppm, respectively, with a signal separation of about 4 ppm. On the other hand, these signals from the spectra of synthetic D-erythro-ceramide and D-glucosyl-D-erythro-ceramide as well as from those of gangliosides, lactosyl-ceramide, galactosyl-ceramide and sphingomyelin are found near 130 ppm and 135 ppm, respectively, thus being apart by about 5 ppm, irrespective of the degree of glycosylation of the ceramide portion. Thus, by carbon-13 NMR spectroscopy the erythro configuration of the sphingoid base in natural sphingolipids is directly demonstrated.