A new xanthone compound fromCentaurium erythraea

Abstract

The PMR spectrum of the compound (0 -- TMS, ~, deuteropyridine, ppm) contained the signals of four aromatic protons: 6.24 (s, IH, H-2); 7.84 (q, J1 = 8 Hz, J= = 3 Hz, IH) corresponding to H-8; and 7.44 (q, J~ = 8 Hz, J2 = 3 Hz, IH) and 7.2 (t, EJ = 16 Hz, IH) refating to H-6 and H-7, respectively. In the 3.74 (s, 3H, OCH3) and 3.96 (s, 3H, OCH3) regions there were the signals of two methoxy groups. In the PMR spectrum of the acetate of the substance (~, CDCI3, ppm), at 2.48 and 2.54 (s, 3H each, --OCOCH3) there were the signals of two acetyl groups, and twomethoxygroups at 3.88 (s, 3H, OCH3) and 4.04 (s, 3H, OCH3). The signal of the methoxy group at 4.04 corresponds to position 3 [2]. The position of the second methoxy group was determined from the mass spectrum. Thus, the mass spectrum contained, in addition to the molecular peak M+ 288 (100%), a peak with m/z 273 (100%), corresponding to M -- 15. The presence of this peak is characteristic for xanthones containing a methoxy group in position 5 [3]. To prove the 1,3,4,5-type of substitution, the initial compound was methylated with diazomethane. This gave l-hydroxy-3,4,5-trimethoxyxanthone, CI~H~Os, M + 302, mp 185-186°C (sublimation of the compound).