Synthesis of Ceramides Bearing DL-erythro- and DL-threo-Cn-Dihydrosphingosines, and the Determination of the erythro and threo Isomers by Mass Spectrometry

Abstract

DL-threo- and DL-erythro-Cn-dihydrosphingosines (n=12, 14, and 16) were separated from the corresponding 2-amino-1, 3-alkanediols by repeated recrystallization of the N, O, O-triacetyl and N-acetyl derivatives. Ceramides having DL-threo- and DL-erythro-Cn-dihydrosphingosines were prepared by reactions of the bases with N-acyloxysuccinimides in tetrahydrofuran. GLC-MS analysis of O, O-di-TMS derivatives of the ceramides was carried out to find differences between threo and erythro isomers in mass spectra. One characteristic difference was observed in the relative intensity (RI) at m/e=M-103; i.e., the relative intensities of threo compounds (RI 4080%) were stronger than those of erythro isomers (RI 614%). The ratios, RI(M-103)/RI(M-15), were 3.76.8 and 0.81.3 for threo and erythro compounds, respectively. These observations demonstrate the possibility of determining erythro and threo isomers by mass spectrometry.