Synthetic approach to pentacyclic quassinoids from communic acids, via ambracetal derivatives |
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Authors: | EJ Alvarez-Manzaneda JL Romera R Alvarez-Manzaneda R Meneses |
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Institution: | a Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain b Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Almería, 04120 Almería, Spain |
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Abstract: | Methyl (8R,13S)-8α,13:13,17-diepoxy-14,15-dinorlabdane-19-oate, easily prepared from communic acids, is a suitable intermediate for synthesizing pentacyclic quassinoids, because it enables the elaboration of the A ring and the further construction of the B-C-D ring system of these terpenoids. The cetal group is stable under the reaction conditions utilized during the elimination of the ester group and the introduction of the hydroxyl group on C-3. At the same time, it enables the regeneration of the methylketone and exocyclic double bond presented by methyl 13-oxo-14,15-dinorlabd-8(17)en-19-oate. The latter compound was previously used to construct the B-C-D-ring of these quassinoids. |
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Keywords: | Quassinoids Labdane diterpenes Acetal cleavage Wolff-Kishner elimination |
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