The 13C-N.M.R. spectra of methyl (methyl O-methyl-α-d-glucopyranosid)uronates

Isolation and Structure of a Monomethylated Ganglioside Possessing Neuritogenic Activity from the Ovary of the Sea Urchin Diadema setosum

“…1). The downfield signal for C-9 (d 69.8) of the NeuAc unit resulting from O-methylation 13) in the 13 C-NMR spectrum of 3 also supports the presence of the methoxy group at C-9 of the NeuAc unit.…”

“…13 C-NMR spectra were recorded on a Jeol GX-270 spectrometer (67.8 MHz) or a Varian Unity-500 spectrometer (125 MHz). Negative-ion FAB-MS spectra were acquired with a Jeol JMS-SX-102 mass spectrometer (xenon atom beam; matrix, triethanolamine).…”

“…Compound 3 exhibits characteristic signals due to the phytosphingosine-type ceramide, 11) with a 2-hydroxy fatty acid and a sugar moiety at C-1 [d 70.3 (C-1), 51.2 (C-2), 76.1 (C-3), 72.2 (C-4), 175.8 (C-1Ј) and 72.2 (C-2Ј)] in its 13 C-NMR spectrum (Fig. 1, Table 1).…”

“…The presence of glucose (Glc) was obvious from the results of the methanolysis of 3 (vide supra). A detailed analysis of the 13 C-NMR spectrum of 3 revealed the Table 1). In the negative FAB-MS of 3, the molecular ion and fragment ion peaks arising from cleavage of the glycosidic linkages of the major component are observed at m/z 1065, 760, and 598, indicating the presence of a disaccharide moiety, NeuAc (Me)→hexose, as shown in Fig.…”

“…The configura- tions of NeuAc and Glc are believed to be a and b on the basis of their anomeric carbon signals (d 100.1 14) , 104.8) in the 13 C-NMR spectrum of 3. In addition, the absolute configuration of the glucose unit was verified as being the D-form using the method of Hara et al 15) Consequently, if NeuAc is assumed to belong to the most commonly found D-series, then compound 3 is the 9-Omethyl-(N-acetyl-a -D-neuraminosyl)-(2→6)-b -D-glucopyranoside of a ceramide, composed of C 18 -phytosphingosine and heterogeneous fatty acids (2-hydroxyoctadecanoic acid as the major component), as shown in Fig.…”