Neighbouring group participation in the reaction of 7-oxo-ent-kaur-16-ene derivatives with diacetoxyiodobenzene. Synthesis of gibberellin analogues |
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Authors: | Braulio M Fraga Carlo BressaVictoria González-Vallejo Sergio SuárezRicardo Guillermo |
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Institution: | a Instituto de Productos Naturales y Agrobiología, CSIC, Avda. Astrofísico F. Sánchez 3, 38206-La Laguna, Tenerife, Canary Islands, Spain b Instituto Universitario de Bio-Orgánica “Antonio González”, Universidad de La Laguna, Tenerife, Spain |
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Abstract: | The reaction of different 7-oxo-ent-kaur-16-ene derivatives with diacetoxyiodobenzene has been evaluated for the preparation of gibberellin analogues. Thus, the reaction of 7-oxo-ent-kaur-16-en-18-oic acid methyl ester (3) with this reagent afforded 4-epi-GA12 dimethyl ester (6). This reaction constitutes a good procedure for the preparation of this type of compounds. In some cases, alternative reactions that led to the introduction in the substrate of a conjugated 5,6-double bond or to the formation of a ketal at the 6-position were also produced. The formation of these compounds, or of gibberellin analogues, depends on the neighbouring group participation of the different C-18 and C-19 substituents at C-4. |
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Keywords: | Diacetoxyiodobenzene ent-Kaur-16-ene Ring contraction Anchimeric assistance 4-epi-Gibberellin A12 |
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