Rauvomines A and B, Two Monoterpenoid Indole Alkaloids from Rauvolfia vomitoria

Abstract

Two unusual normonoterpenoid indole alkaloids rauvomine A (1) and rauvomine B (2), together with two known compounds peraksine (3) and alstoyunine A (4), were isolated from the aerial parts of Rauvolfia vomitoria. The structures with absolute configurations of 1 and 2 were elucidated by spectroscopic analysis, single-crystal X-ray diffraction, and electronic circular dichroism (ECD) calculations. Compound 2 is a novel C normonoterpenoid indole alkaloid with a substituted cyclopropane ring that forms an unusual 6/5/6/6/3/5 hexcyclic rearranged ring system. The plausible biogenetic pathways of 1 and 2 were proposed. Compound 2 exhibited significant anti-inflammatory activity.

Deploying Microbial Synthesis for Halogenating and Diversifying Medicinal Alkaloid Scaffolds

“…Bioprospecting for promiscuous homologs may also prove fruitful. In the case of MIAs, the identification of two naturally occurring chlorinated alkaloids suggests that evolution may have already provided halo-tolerant enzymes and that screening alkaloid-producing plants native to halogen-rich habitats (e.g., coastal and volcanic soils) may save a significant amount of protein engineering (Al-Khdhairawi et al, 2017;Zeng et al, 2017).…”

Cytotoxic Yohimbine‐Type Alkaloids from the Leaves of Rauvolfia vomitoria

“…[7,8] Previous phytochemical studies of R. vomitoria have revealed the presence of a serious of yohimbine-type, ajmalinetype, and sarpagine-type MIAs. [8,9] In our recent work, a series of yohimbine analogs were discovered from the stems of R. vomitoria (butanol extract) for the first time. [10,11] Continuing to search for new biologically active MIAs, especially yohimbine analogs, the leaves of R. vomitoria were chemically investigated, which led to the isolation of two new MIAs (1 -2) and six known analogs (3 -8) (Figure 1).…”

“…Rauvolfia vomitoria Afzel., widely distributed in Yunnan, Guangzhou, and Guangxi provinces, China, was used as a traditional folk medicine for a long history to treat hypertension, pain, epilepsy, high fever, and gastrointestinal diseases [7,8] . Previous phytochemical studies of R. vomitoria have revealed the presence of a serious of yohimbine‐type, ajmaline‐type, and sarpagine‐type MIAs [8,9] . In our recent work, a series of yohimbine analogs were discovered from the stems of R. vomitoria (butanol extract) for the first time [10,11] .…”

The Ambidextrous Pictet–Spengler Reaction: Access to the (+)- or (–)-Enantiomers of the Bioactive C-19 Methyl-Substituted Sarpagine/Macroline/Ajmaline Alkaloids from Either d- or l-Tryptophan

“…This series of intermediates 26, 31, and 32 are the enantiomers of the intermediates 17, 22, and 23, respectively, which were previously synthesized from the same starting material 33 (see the Supporting Information, SI for comparisons of the NMR spectra of the enantiomeric pairs). 26,27 These intermediates are the key bicyclo[3.3.1] systems required for the total synthesis of the unnatural enantiomers of the Figure 1 Representative examples of bioactive C-19 methyl-substituted sarpagine/macroline/ajmaline alkaloids 13,15,16,[31][32][33][34][35][36][37][38][39][40] On the other hand, the (R,R,R) intermediates in either the N a -H or N a -Me series 24, 25, 27-30 were synthesized from the corresponding N b -propargyl-substituted D-tryptophan derivative 36, 26,27 as shown in Scheme 3. The Pictet-Spengler reaction, N a -methylation, Dieckmann cyclization, decarboxylation, and TIPS deprotection went smoothly to furnish the desired intermediates in good to excellent yields (Scheme 3).…”