- Synthesis and Structural Elucidation of Coumarinolignans
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Coumarinolignans are a relatively new class of natural products combining a coumarin skeleton with a phenylpropene moiety.We describe here details of the first biomimetic syntheses of compounds in this series (1-16) utilizing both chemical and enzymatic approaches and the application of the selective INEPT nmr technique for unambiguous structure assignment.Chemical oxidation using silver oxide as an oxidizing agent typically produced two regioisomeric trans-substituted coumarinolignans.Enzymatic oxidation on the other hand normally gave rise to a single regioisomer.Almost all of the known natural coumarinolignans and several new compounds which may subsequently be obtained as natural products were synthesized.Three nmr strategies are described for the structure elucidation of the coumarinolignans, but only one of these techniques, the selective INEPT method, affords an unambiguous structure when only one regioisomer is present.Using this technique the structures and complete proton and carbon-13 chemical shift assignments of sixteen synthetic coumarinolignans were established.The described nmr strategy should prove useful for the unambiguous structure determination of all natural 2-aryl benzodioxanes, including the flavonolignans, the xanthonolignans and certain neolignans.
- Lin, Lee-Juian,Cordell, Geoffrey A.
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p. 3052 - 3080
(2007/10/02)
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- SYNTHESIS OF THE NATURAL COUMARINOLIGNOIDS PROPACIN AND CLEOMISCOSIN A AND B. AN EMPIRICAL SPECTROSCOPIC METHOD TO DISTINGUISH REGIOISOMERS OF NATURAL BENZODIOXANE LIGNOIDS
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The synthesis of the title coumarinolignoids by Ag2O oxidation of fraxetin and isoeugenol or coniferyl alcohol is reported.A simple diagnostic method based on 13C nmr spectra is proposed to distinguish regioisomers of natural benzodioxane lignoids.
- Arnoldi, Anna,Arnone, Alberto,Merlini, Lucio
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p. 1537 - 1544
(2007/10/02)
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- Synthesis of Coumarinolignans through Chemical and Enzymic Oxidation
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The first syntheses of coumarinolignans through chemical or enzymic oxidation of a dihydroxycoumarin and a phenylpropene are described.
- Lin, Lee-Juian,Cordell, Geoffrey A.
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p. 160 - 161
(2007/10/02)
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