Efficient assembly of 3-substituted oxindole-based isoxazolines leading to the synthesis of (±)-flustraminol-B and related natural product building blocks

An efficient synthesis of oxindole-based isoxazolines has been developed and the resulting spirocyclic intermediates have been elaborated to synthetically versatile 3-hydroxy-3-alkyl oxindole building blocks such as the 3-hydroxy-3-methylenecyano-2-oxindoles (6) and γ-amino alcohols (12). Utility of this methodology is demonstrated through the synthesis of pyrrolo[2,3-b]indolines including the marine natural product (±)-flustraminol-B.