Synthesis from L-glucal

Photolytic oxidative cyclization followed by iodination afforded the iodo derivative 20, which was subjected to (3-elimination using DBU in THE to furnish the olefin 21. 

Treatment of 21 with potassium ferf-butoxide and iodine produced 22. Radical deiodi-nation of 22 followed by hydrogenation and subsequent treatment with sodium methoxide in methanol provided 23. Selective protection of the oxazolidinone ring in 23 with Boc followed by protection of imide with BOMCl afforded 24, which was treated with cesium 

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