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Condensation of hydroxypyridone 7 with ethyl pyruvate and p-chlorothiophenol, reduction, and cyclization afforded 77% of lactone 6. Protection of the pyridone, acylation of the enolate with tigloyl chloride, and deprotection provided keto lactone 22. Reduction and dehydrative cyclization completed short and efficient syntheses of 2 and 3.
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Snider et al. (2004) studied this question.
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