Towards EPC-syntheses of the structural class of cochleamycins and macquarimicins. Part 3: EPC-syntheses of the β-keto lactone subunits and first attempts towards the syntheses of the pentacyclic antibiotics of this group |
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Authors: | A Chrobok K Grünberger H Kählig MJ White F Wuggenig |
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Institution: | Institut für Organische Chemie der Universität Wien, Währingerstraße 38, A-1090 Vienna, Austria |
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Abstract: | Practical EPC-syntheses of δ-substituted-β-keto δ-lactones, subunits of the cochleamycins and macquarimicins, are presented. In consequence Tietze's tandem reaction is employed to combine δ-allyl-β-keto δ-lactone with a hydrindene derivative, the second subunit of these acetogenic antibiotics. Model reactions for the final oxidative radical tandem cyclization reveal that the electrophilic radical cyclizes exclusively in exo-trig fashion. However, with the intended precursor of macquarimicin C allylic hydrogen abstraction thwarted the oxidative radical tandem cyclization. |
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Keywords: | Macquarimicin EPC-syntheses of δ-substituted-β-keto δ-lactones Tandem Knoevenagel/hetero-Diels-Alder reaction Regiochemistry of oxidative radical cyclization Allyl oxidation |
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