Untersuchungen zur Synthese des Nodusmicin, I: Darstellung von (�)-(1R*,5R*,6R*,7S*8R*,9R*,10R*)-5-Acetyl-7,9-dibenzyloxy-10-hydroxy-8-methylbicyclo[4.4.0]decan-3-on
作者:E. G�ssinger、M. Graupe、K. Zimmermann
DOI:10.1007/bf00816420
日期:——
Our first target on the way towards the synthesis of nodusmicin is the preparation of the title compound. Meso diol 1 is partially etherified, then oxidized to the enone. The sterically compressed structure of this compound is the rationale of the highly stereoselective introduction of the substituents. (CH3)2CuLi introduces the methyl group and the enolate is captured as silylenol ether, which in turn is transformed to the alpha-hydroxyketone by OsO4. Reduction leads to the vicinal trans diol. Protection of the exo-hydroxy group is followed by treatment with sodium in ethanol. Via intramolecular nucleophilic addition, substitution and dechlorination the tetracyclic diketal 8 is formed. After exchange of the protective groups and partial hydrolysis of the ketals the tertiary alkohol is obtained with methyl Grignard reagent. Acidic fragmentation yields the desired title compound.