Rauvotetraphyllines A-E, new indole alkaloids from Rauvolfia tetraphylla

Abstract

Abstract:Five new indole alkaloids rauvotetraphyllines A-E (1-5), together with eight known analogues, were isolated from the aerial parts of Rauvolfia tetraphylla. The structures were established by means of spectroscopic methods.

Indole alkaloids from the Marquesan plant Rauvolfia nukuhivensis and their effects on ion channels

“…First the coupling constants obtained between the H 2 -6, H-5 and H-16 protons of 11 were very close to those reported for rauvoyunine A thus confirming the same 5S and 16R configurations at these positions (Gao et al, 2011). Starting now from H-3 here also the coupling constants between H-3, H-14a and H-14b obtained for 11 were similar to those reported for the same alkaloid but also for its analogue rauvotetraphylline A (Gao et al, 2012). In particular, for 11 and these two previously described compounds, the signal corresponding to H-14a appears as a broad triplet with coupling constant around 13 Hz, while it appears as a doublet with the same 3 J for H-14b.…”

“…We then decided to focus on the few coupling constants available for the protons of this bicycle. Comparison of these data with those described for two macroline analogues helped us to propose a configuration at C-15 (Gao et al, 2011(Gao et al, , 2012. First the coupling constants obtained between the H 2 -6, H-5 and H-16 protons of 11 were very close to those reported for rauvoyunine A thus confirming the same 5S and 16R configurations at these positions (Gao et al, 2011).…”

“…From a structural point of view, most of these bioactive alkaloids are found under an additional cyclized form that occurs between an oxygen placed at C-17 and the C-21 carbon (Bi et al, 1994;Liao et al, 2006;Lim et al, 2014;Tran and Kwon, 2005;Wilk et al, 2009). The postulated non cyclized product called macroline that should be at the origin of all macroline derivatives has never been found in nature but two close analogues of this putative precursor have been reported (Gao et al, 2011(Gao et al, , 2012. The presence of a third non cyclized monomer in R. nukuhivensis confirms the biosynthetic connection of this family with the sarpagine and ajmaline types of indole alkaloids.…”

Hybrid Monoterpenoid Indole Alkaloids Obtained as Artifacts from Rauvolfia tetraphylla

“…The 1D-NMR spectra (Tables 1 and 3 ) revealed the presence of an unsubstituted indole moiety [ δ H 7.38 (1H, d, J = 7.8 Hz), 7.26 (1H, d, J = 8.0 Hz), 7.02 (1H, dd, J = 8.0, 7.3 Hz), and 6.95 (1H, dd, J = 7.8, 7.3, Hz); δ C 139.7 (s), 138.2 (s), 128.9 (s), 121.9 (d), 119.7 (d), 118.5 (d), 111.9 (d), and 104.0 (s)], an ethylidene group [ δ H 1.75 (3H, d, J = 6.9 Hz) and 5.93 (1H, q, J = 6.9 Hz); δ C 14.3 (q) and 125.2 (d)], and a glucose unit [ δ H 4.64 (1H, d, J = 7.9 Hz), 3.29 (1H, m), 3.37 (1H, m), 3.28 (2H, m), 3.60 (1H, dd, J = 11.9, 4.9 Hz), and 3.74 (1H, dd, J = 11.9, 1.6 Hz); δ C 103.2 (d), 78.0 (d), 77.9 (d), 75.4 (d), 71.4 (d), and 62.7 (t)]. Comparison of its 13 C NMR data with those of rauvotetraphylline B [ 6 ] revealed a remarkable resemblance except for a prominent difference as follows: the carbon signals assigned to 4,6-dimethylpyrid-2-yl unit in rauvotetraphylline B were not present, and there was a set of newly arisen resonances [ δ C 56.5 (d), 47.4 (t), 213.2 (s), 55.7 (t), 55.5 (s), 25.6 (q), and 31.9 (q)] determined as a 2,2-dimethyl-4-oxopiperidin-6-yl moiety by HMBC correlations (Fig. 1 ) from H-17 to C-23, H-22 to C-23 and C-24, and H-24 to C-22, C-23, C-25, C-26, and C-27.…”

“…Plants of this genus are a rich source of monoterpenoid indole alkaloids, which have attracted great interests from biological and therapeutic aspects [ 2 – 5 ]. As part of a BioBioPha [ http://www.chemlib.cn ] objective to assemble a large-scale natural product library valuable in the discovery of new drug leads from nature, previous chemical study on the ethanolic extract of Rauvolfia tetraphylla had resulted in the isolation of five new indole alkaloids, rauvotetraphyllines A–E [ 6 ]. Further investigation of the remaining components led to the isolation of another five new alkaloids bearing an unusual 2,2-dimethyl-4-oxopiperidin-6-yl moiety, rauvotetraphyllines F–H ( 1 , 3 , 4 ), 17- epi -rauvotetraphylline F ( 2 ) and 21- epi -rauvotetraphylline H ( 5 ).…”