Abstract
D-ribo-C18-Phytosphingosine (Phyto) reacted with acetone to give Phyto-acetone adducts (1) whose structures were determined by mass spectrometry. In the DI-MS analysis of the Phyto-acetone-h6 adduct (1-h6), significant fragment ions at m/e=326 (M-CH2OH) and 342 (M-CH3) were observed in addition to those previously reported ions, m/e=100, 130 and 160. The reaction of the adduct (1-h6) with HMDS+TMCS in pyridine gave two products, the bis-TMS derivative of 2, 3-cyclic adduct (III) and the tris-TMS derivative of the ring-opening compound (V) formed by the ring-opening reactions of (III) and 3, 4-bis-TMS derivative of 1, 2-cyclic adduct (IV) with TMS. The structures of (III) and (V) were determined by GC-MS analysis. The TMS derivative (III) reacted with another molecule of TMS to give (IV), which was confirmed by GLC analysis. The rate for the ring-opening of (III) by TMS may possibly be slower than that of (IV) because of the steric hindrance of the proposed structures. In the DI-MS analysis of the Phyto-acetone-d6 adduct (1-d6), the fragment ions in 1 or 2 mass numbers larger than those expected were observed. This suggests an electron impact H-D exchange reaction at OH groups in the mass chamber. On the basis of these findings, it is concluded that there exists a 2, 3-cyclic compound (II) in addition to the previously reported 1, 2-cyclic compound (I), as the structure of (1).
