The first synthesis of marinopyrrole B, which is highly active against methicillin-resistant Staphylococcus aureus, is described. The route involved constructing a pyrrole ring on the nitrogen of a 3-bromo-4,5-dichloropyrrole by N-alkylation with a special Michael acceptor having an allylic leaving group; the second pyrrole ring was then formed by a Paal-Knorr reaction.
Reaction of acetylides with aldehydes to form but-2-yne-1,4-diols, followed by triple bond reduction and oxidation of the hydroxyl groups, gives 1,4-diketones; these react with vinyllithium, and the resulting diols undergo ring-closing metathesis to form 2-cyclohexene-1,4-diols. Dehydration, usually by acid treatment, then gives benzenes carrying substituents in a 1,4 relationship. Use of substituted vinyllithiums provides further substitution on the final benzene rings. The method can be applied to the synthesis of C5-aryl carbohydrates.
Intramolecular conjugate displacement (ICD) has been applied to the Morita-Baylis-Hillman adducts formed from (5S)-5-(l-menthyloxy)-2(5H)-furanone and aldehydes that carry a protected β- or γ-amino group. DIBAL-H reduction of the resulting ICD products releases optically pure six- or seven-membered cyclic amines having a stereogenic center α to nitrogen.
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