The total syntheses of eight members of the palmarumycin family have been achieved, with identification of the absolute stereochemistry for three of these natural products. In addition, the ras-farnesyl transferase inhibitor (-)-preussomerin G has been synthesized, achieving the first enantioselective route for accessing this family of natural products. Highlights of the synthetic work include an asymmetric epoxidation of a cyclic enone in excellent yield and enantiomeric excess and a potentially biomimetic oxidative spirocyclization for the introduction of the bis-spiroketal array unique to the preussomerin natural products.
The beta-adrenergic agonist 1 (zilpaterol) is used as production enhancer in cattle. Binding experiments of separated enantiomers on recombinant human beta(2)-adrenergic and mu-opioid receptors and functional studies showed that the (-)-1 enantiomer accounts for essentially all the beta(2)-adrenergic agonist activity and that it exhibits less affinity toward the mu-opioid receptor than (+)-1, which is a mu-opioid receptor antagonist. X-ray crystallography revealed the absolute configuration of (-)-1 to be 6R,7R.
A general synthetic route to the enantiopure bicyclic cyclopentadienes (S)‐3 and (R)‐3 of the hydrindane series, starting from the Hajos‐Wiechert ketone 4 or its enantiomer is described. Reasons for the excellent face and endo selectivity of cycloadditions and the resulting consequences for chiral recognition are discussed.
Investigations towards the solid-phase synthesis of 1,2diketones via the oxidation of acetylenes and their use in the combinatorial synthesis of heterocycles such as imidazoles and quinoxalines are described.
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