- Synthesis of the Mammea Coumarins. Part 4. Stereochemical and Regiochemical Studies, and Synthesis of (-)-Mammea B/BB
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Acylation of phloroglucinol with (S)-2-methylbutyryl chloride followed by Pechmann condensation with ethyl 3-oxohexanoate, or acylation of 5,7-dihydroxy-4-propylcoumarin with (S)-2-methylbutyryl chloride gave an 8-(S)-acylcoumarin that was C-alkylated to afford natural (-)-mammea B/BB: the configuration of the 2-methylbutyryl moiety in the natural coumarins was thus demonstrated to be (S)-Surangin B was likewise prepared as a mixture of 1'S, 2''S)- and (1'R, 2''S)-stereoisomers.The crystal structure and conformation of a 6-acylcoumarin that establishes the orientation of other synthetic coumarins is reported.
- Crombie, Leslie,Jones, Raymond C. F.,Palmer, Christopher J.,Begley, Michael J.
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p. 353 - 358
(2007/10/02)
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- Synthesis of Mammea Coumarins. Part 1. The Coumarins of the Mammea A, B, and C Series
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The naturally-occuring Mammea coumarins of the 4-phenyl-(mammea A), propyl-(mammea B), and 4-pentyl-(mammea C) series have been prepared by Pechmann condensation of an acylphloroglucinol (3-methylbutyryl-, 2-methylbutyryl-, butyryl-, or 2-methylpropionyl-) with the appropriate β-ketoester to give a mixture of 6- and 8-acyl-5,7-dihydroxycoumarins that could be separated.C-Alkylation with 3-methylbut-2-enyl bromide, or 3,7-dimethylocta-2,6-dienyl chloride, in aqueous potassium hydroxide completed the synthesis of the Mammea coumarins having unmodified prenyl or geranyl substituents; oxidative modification of the prenyl group led to the mammea cyclo E and cyclo F coumarins.Some mammea cyclo D (chromeno) coumarins were synthesized by reaction of acylcoumarins with 1,1-dimethoxy-3-methylbutan-3-ol.
- Crombie, Leslie,Jones, Raymond C. F.,Palmer, Christopher J.
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p. 317 - 332
(2007/10/02)
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