A Novel Route to 5-Substituted 3-Isoxazolols. Cyclization of N,O-DiBoc β-Keto Hydroxamic Acids Synthesized via Acyl Meldrum's Acids
Ulrik S. Sørensen, Erik Falch and Povl Krogsgaard-Larsen*
*NeuroScience PharmaBiotec Research Centre, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, 2 Universitetsparken, DK-2100 Copenhagen, Denmark, Email: pklsund.ku.dk
U. S. Sørensen, E. Falch, P. Krogsgaard-Larsen, J. Org. Chem., 2000, 65, 1003-1007.
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Hydrochloric acid mediates a cyclisation of N,O-diBoc-protected β-keto hydroxamic acids to 5-substituted 3-isoxazolols without formation of any 5-isoxazolone byproduct. The N,O-diBoc-protected β-keto hydroxamic acids are obained by a versatile three-step procedure from carboxylic acid derivatives.
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