19-Oxodeltaline, a norditerpene alkaloid from the aerial part of Delphinium uralense

Abstract

The IR spectrum of 1 indicated hydroxyl (3300–3500 cm–1), ester (1736), and amide (1622) groups were present. High-resolution mass spectrometry found that 1 had the formula C27H39NO9, [M] + 521.263. The mass spectrum of 1 had series of peaks characteristic for lycoctonine compounds in addition to a medium-intensity peak for [M – 59]+. PMR spectra of 1 were consistent with three methoxyls ( 3.21, 3.32, 3.42 ppm), methyl of N-ethyl (1.11), and methylenedioxy (4.90, 4.92). A 1H singlet at 5.38 ppm in addition to a 3H singlet at 2.04 in the PMR spectrum of 1 indicated that C-6 contained a -OAc group [5]. A weak-field shift of the characteristic triplet for H-14 (4.13, J = 4.8 Hz) suggested that C-14 had an -methoxyl; C-10, a -OH group [6]. The appearance in the 13C NMR spectrum of the resonance for C-19 at 172.8 ppm and a strong-field shift of the N–CH2 resonance to 42.9 confirmed that C-19 had an oxo group. A 3H singlet in the PMR spectrum at 1.20 and a resonance at 21.5 in the 13C NMR spectrum were consistent with a methyl group on C-4 in 1. The PMR, 13C NMR, IR, and mass spectra for 19-oxodeltaline (1), which was isolated for the first time from a plant, were identical to those for synthetic 19-oxodeltaline [4], which was prepared by us from deltaline (2) by KMnO4 oxidation in aqueous acetone. IR spectra were recorded in mineral oil on a Specord M-82 spectrometer. Mass spectra (EI, 70 eV) were obtained in a Thermo Finnigan MAT 95 XP mass spectrometer by matching peaks. PMR and 13C NMR spectra were recorded in CDCl3 on a Bruker AMX III-300 instrument (300.13 MHz) with Me4Si internal standard.