Progress on Olefin Cross Metathesis in the Synthesis of a Betanin Analog

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Title: Progress on Olefin Cross Metathesis in the Synthesis of a Betanin Analog
Author: Nuyen, Laura
Advisor: Newirth, Terry
Department: Haverford College. Department of Chemistry
Type: Thesis (B.S.)
Issue Date: 2008
Abstract: Betanin is the primary red/violet pigment found in beets, and other plants, and part of the betalain family. A betanin analog is desirable so that we may test its sensitivity towards nucleophiles, in particular thiols. First we aim to synthesize an analog of betalamic acid, (Z)-methyl 4-(2-oxoethylidene)-1,4,5,6-tetrahydropyridine-2-carboxylate (10),which should react spontaneously with proline to give our target compound, (S,Z)-2-carboxy-1-((Z)-2-(6-(methoxycarbonyl)-2,3-dihydropyridin-4(1H)-ylidene)ethylidene)pyrrolidinium. Previous to this year, we had synthesized (2S)-N-(tertbutoxycarbonyl)-2-methoxycarbonyl-4-oxopiperidine (6), and current work is being done to oxidize the ring and extend the electrophilic -highway. Olefin metathesis, the rearrangement of the carbon atoms of two C=C bonds, is one route we are pursuing to attach an aldehyde to 1-Boc-4-methylene-2-piperidinemethylester (7). Test reactions between 1-t-butyl-4-methylene-cyclohexane and acrolein dimethyl acetal (ADMA) resulted in the dimerization of ADMA, which did not participate in further CM reactions. Test reactions between 1-t-butyl-4-methylene-cyclohexane and crotonaldehyde resulted in high yields of the desired product with very little byproducts. An attempt to isolate the product resulted in 93% yield with impurities. We obtained NMR evidence that our reaction was successful and the reaction is reproducible. The results of reactions between 7 and crotonaldehyde were skewed due to an excess amount of catalyst that resulted in unexpected byproducts. However, it is evident from GC-MS analysis that both CM products are forming, with the desired product (Z)-1-tert-butyl 2-methyl 4-(2-oxoethylidene)piperidine-1,2-dicarboxylate (8) forming 2:1 in comparison with the other CM product 22. Further experiments with decreased catalyst loading and improved stoichiometry are likely to lead to very positive results.
Subject: Metathesis (Chemistry)
Subject: Alkenes
Subject: Betanin -- Synthesis
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Nuyen, Laura. "Progress on Olefin Cross Metathesis in the Synthesis of a Betanin Analog". 2008. Available electronically from

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