- Synthesis of New Macrocycles. Part 6. Pyridine-retronecate, a New Synthetic Alkaloid
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Reaction of 2,6-bis(bromomethyl)pyridine with the naturally-occuring C10 necic acid, retronecic acid, results in the formation of a new semi-synthetic cyclic diester alkaloid, pyridine-retronecate.This product is an analogue of a pyrrolizidine alkaloid and retains those characteristics normally held responsible for the toxity of this class of alkaloids.Biological tests carried out on mice injected with retrorsine and with the synthetic analogue suggest that the cytotoxic effects are similar.
- Drewes, Siegfried E.,Pitchford, Andrew T.
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- Pyrrolizidine Alkaloid Biosynthesis. Synthesis of 3H-Labelled Trachelanthamidine and Isoretronecanol and their Incorporation into Three Pyrrolizidine Bases (Necines)
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(+/-)-Isoretronecanol (22) and (+/-)-trachelanthamidine (24) were prepared by 1,3-dipolar cycloaddition of N-formylproline with ethyl propiolate followed by reduction steps.These 3H-labelled 1-hydroxymethylpyrrolizidines together with putrescine were fed to Senecio isatideus which produces retrorsine (1); S. pleistocephalus which yields rosmarinine (8); and Cynoglossum officinale which affords echinatine (5).The double labelling experiments demonstrated that isoretronecanol is incorporated much more efficiently into rosmarinine than into retrorsine or echinatine, whereas trachelanthamidine is a much more efficient precursor for retrorsine and echinatine.Base hydrolysis of retrorsine and echinatine labelled with trachelanthamidine and of rosmarinine labelled with isoretronecanol established that most of the 3H-label was in the base portions, retronecine (2), heliotridine (6), and rosmarinecine (9), respectively.Further degradation of retronecine and rosmarinecine showed that most of the radioactivity was confined to the β-alanine (4) portion.The biosynthetic pathways to isoretronecanol and trachelanthamidine apparently diverge prior to the formation of these 1-hydroxymethylpyrrolizidines, probably during the cyclisation of an immonium ion (14) to form the 1-formylpyrrolizidines (15) and (17).
- Kunec, Ellen K.,Robins, David J.
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p. 1437 - 1441
(2007/10/02)
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- Necic Acid Synthons. Part 5. Total Synthesis of (+/-)-Retronecic Acid and Related Compounds via Zinc-Mediated Coupling of Halogeno-esters
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Zinc-mediated coupling of suitably substituted halogeno esters affords access to (+/-)-retronecic acid (2) and related intermediates.These approaches lead to racemic retronecic acid on the one hand and to a diastereoisomeric mixture of the acid on the other.
- Ameer, Farouk,Drewes, Siegfried E.,Hoole, Robyn,Kaye, Perry T.,Pitchford, Andrew T.
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p. 2713 - 2718
(2007/10/02)
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