Subtopic Deep Dive
Total Synthesis of Stemona Alkaloids
Research Guide
What is Total Synthesis of Stemona Alkaloids?
Total synthesis of Stemona alkaloids involves developing stereoselective routes to construct the pyrrolo[1,2-a]azepine cores of these natural products isolated from Stemonaceae plants.
Stemona alkaloids feature complex polycyclic structures with biological activities including antitussive and antiparasitic effects (Greger, 2006; 210 citations). Key syntheses include asymmetric routes to (-)-stenine (Wipf et al., 1995; 137 citations) and (+)-croomine (Williams et al., 1989; 134 citations). Over 10 total syntheses reported since 1989 target diverse family members using Diels-Alder, radical cyclizations, and aza-Wittig strategies.
Why It Matters
Syntheses validate antitussive activity of Stemona alkaloids for traditional Asian medicine and provide antiparasitic leads (Greger, 2006). Wipf's 24-step route to (-)-tuberostemonine (Wipf et al., 2002; 102 citations) demonstrates scalable access to pentacyclic cores for SAR studies. Strategies like Hart's Diels-Alder approach to stenine (Chen and Hart, 1993; 79 citations) and Aggarwal's boryl pyrrolidine homologation for (-)-stemaphylline (Varela et al., 2017; 78 citations) advance stereocontrol in alkaloid synthesis, enabling analog development for drug discovery.
Key Research Challenges
Stereocontrol in azepine formation
Constructing the central pyrrolo[1,2-a]azepine with precise stereochemistry challenges asymmetric catalysis and cyclization tactics. Wipf et al. (1995) used chiral auxiliaries for (-)-stenine, but scaling remains difficult. Recent boryl-mediated rearrangements address this (Varela et al., 2017).
Polycyclic core assembly
Building fused pyrrole-piperidine-azepine rings requires efficient cascades to minimize steps. Williams et al. (1989) achieved (+)-croomine via tandem processes, yet pentacyclic variants like tuberostemonine demand innovative silyl enol ether strategies (Wipf et al., 2002). Biomimetic approaches often fail scalability.
Functional group compatibility
Sensitive α-tertiary amines and enol ethers limit reagent choices in late-stage transformations. Hager et al. (2015; 190 citations) highlight ATA motif challenges across alkaloids. Chen et al. (2011; 67 citations) used semipinacol rearrangements but faced protection issues.
Essential Papers
Structural Relationships, Distribution and Biological Activities of<i>Stemona</i>Alkaloids
Harald Greger · 2006 · Planta Medica · 210 citations
Stemona alkaloids represent a unique class of natural products exclusively isolated from the monocotyledonous family Stemonaceae comprising three genera mainly distributed in southeast Asia. Struct...
Synthetic approaches towards alkaloids bearing α-tertiary amines
Anastasia Hager, Nina Vrielink, Dominik Hager et al. · 2015 · Natural Product Reports · 190 citations
The α-tertiary amine (ATA) is a prominent structural motif in many well-known alkaloids. Its chemistry is comprehensively reviewed.
Asymmetric Total Synthesis of the Stemona Alkaloid (-)-Stenine
Peter Wipf, Yun-Tae Kim, David Goldstein · 1995 · Journal of the American Chemical Society · 137 citations
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAsymmetric Total Synthesis of the Stemona Alkaloid (-)-SteninePeter Wipf, Yuntae Kim, and David M. GoldsteinCite this: J. Am. Chem. Soc. 1995, 117, 45, 1...
Studies of Stemona alkaloids. Total synthesis of (+)-croomine
David R. Williams, David Brown, John W. Benbow · 1989 · Journal of the American Chemical Society · 134 citations
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudies of Stemona alkaloids. Total synthesis of (+)-croomineDavid R. Williams, David L. Brown, and John W. BenbowCite this: J. Am. Chem. Soc. 1989, 111,...
Total Synthesis of (−)-Tuberostemonine
Peter Wipf, Stacey R. Rector, Hidenori Takahashi · 2002 · Journal of the American Chemical Society · 102 citations
The first total synthesis of the complex pentacyclic Stemona alkaloid tuberostemonine was accomplished in 24 steps and in 1.4% overall yield from a hydroindole intermediate which is readily obtaine...
Recent progress in the synthesis of heterocyclic natural products by the Staudinger/intramolecular aza-Wittig reaction
Shoji Eguchi · 2005 · ARKIVOC · 98 citations
A review of recent progress in the synthesis of heterocyclic natural products by the aza-Wittig method focusing on applications of the tandem Staudinger/intramolecular aza-Wittig reaction.
A Diels-Alder approach to Stemona alkaloids: total synthesis of stenine
Cheng‐Yi Chen, David J. Hart · 1993 · The Journal of Organic Chemistry · 79 citations
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA Diels-Alder approach to Stemona alkaloids: total synthesis of stenineCheng Yi Chen and David J. HartCite this: J. Org. Chem. 1993, 58, 15, 3840–3849Pub...
Reading Guide
Foundational Papers
Start with Greger (2006; 210 citations) for structures and bioactivity, then Wipf (1995; 137 citations) for asymmetric stenine and Williams (1989; 134 citations) for croomine to grasp core strategies.
Recent Advances
Study Varela (2017; 78 citations) for boryl methods in stemaphylline and Chen (2011; 67 citations) for maistemonine to see stereocontrol advances.
Core Methods
Core techniques: Diels-Alder cycloadditions (Chen and Hart, 1993), semipinacol tandem reactions (Chen et al., 2011), aza-Wittig cascades (Eguchi, 2005), and metal carbenoid homologations (Varela et al., 2017).
How PapersFlow Helps You Research Total Synthesis of Stemona Alkaloids
Discover & Search
Research Agent uses searchPapers('total synthesis Stemona alkaloids') to retrieve Greger (2006; 210 citations), then citationGraph to map syntheses from Wipf (1995), and findSimilarPapers for unpublished routes. exaSearch uncovers variants like maistemonine from Chen (2011).
Analyze & Verify
Analysis Agent applies readPaperContent on Wipf (2002) to extract 24-step yield data, verifyResponse with CoVe against Greger (2006) for bioactivity claims, and runPythonAnalysis to plot stereoselectivity trends across 10 syntheses using pandas. GRADE grading scores route efficiency (e.g., steps vs. yield).
Synthesize & Write
Synthesis Agent detects gaps like scalable tuberostemonine analogs via contradiction flagging between Wipf (2002) and recent reviews. Writing Agent uses latexEditText for scheme revisions, latexSyncCitations to integrate 15 papers, latexCompile for publication-ready routes, and exportMermaid for cyclization cascades.
Use Cases
"Analyze step economy in Stemona syntheses: Wipf stenine vs Williams croomine"
Research Agent → searchPapers → Analysis Agent → runPythonAnalysis (pandas comparison of steps/yields from 137+134 citation papers) → matplotlib yield plot output.
"Draft total synthesis scheme for (-)-stemaphylline with citations"
Synthesis Agent → gap detection → Writing Agent → latexGenerateFigure (boryl homologation) → latexSyncCitations (Varela 2017) → latexCompile → PDF scheme.
"Find code for modeling Stemona azepine conformations"
Research Agent → paperExtractUrls (Wipf 2002 supp) → paperFindGithubRepo → githubRepoInspect → runPythonAnalysis (sandbox DFT optimization output).
Automated Workflows
Deep Research workflow scans 50+ Stemona papers via searchPapers → citationGraph → structured report ranking syntheses by yield (Wipf 1.4%). DeepScan's 7-step chain verifies Aggarwal (2017) metalate rearrangement with CoVe against Hager (2015) ATA review. Theorizer generates biomimetic cascade hypotheses from Greger (2006) structures.
Frequently Asked Questions
What defines Stemona alkaloids?
Stemona alkaloids are polycyclic natural products with pyrrolo[1,2-a]azepine cores from Stemonaceae plants in southeast Asia, showing antitussive activity (Greger, 2006; 210 citations).
What are key synthesis methods?
Methods include Diels-Alder (Chen and Hart, 1993), asymmetric catalysis (Wipf et al., 1995), and boryl homologation (Varela et al., 2017) for stereocontrol.
What are seminal papers?
Greger (2006; 210 citations) classifies structures; Wipf (1995; 137 citations) first asymmetric stenine; Williams (1989; 134 citations) croomine.
What open problems exist?
Scalable syntheses of pentacyclic members like tuberostemonine (Wipf, 2002) and late-stage diversifiable ATAs remain unsolved (Hager et al., 2015).
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