Studies Directed at the Synthesis of Optically Active Pretazettine via Intramolecular Nitrone/Alkene Cycloaddition Reactions
A protocol for the synthesis of optically active pretazettine which focuses on both the control of relative stereochemistry between the angular aryl and C6a hydroxyl groups and absolute stereochemistry has been developed and executed. The synthesis of the 1,3-dithiane ketal of (Z)-ethyl 3-(1,3-benzodioxol-5-yl)-5,7-dioxo-2-heptanoate is described. Treatment of this alkene aldehyde with N-(α-methylbenzyl)hydroxylamine afforded a nitrone, which underwent intramolecular 1,3-dipolar cycloaddition to afford the two diastereomeric isoxazolidine cycloadducts in a 16:1 ratio. The sense of chirality transfer was determined by a single-crystal X-ray analysis of the major isomer. © 1991, American Chemical Society. All rights reserved.
Baldwin, SW; McPhail, AT; Aubé, J
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