| Sumario: | 2-Acetamido-4,6-O-benzylidene-2,3-dideoxy-D-erythro-hex-2-enono-1,5-la ctone (2), readily prepared from D-glucosamine, undergoes a rearrangement on treatment with tin(IV) chloride which leads to 3-acetamido-2-pyrone (3) and 2-acetamido-2,3-dideoxy-4,6-O-formylidene-D-threo-hex-2-enono-1,5-lact one (4). A mechanism is proposed for this unusual rearrangement, which was not observed for other analogous hex-2-enono-1,5-lactones. For example, the 2-acetoxy analog of 2 (2-acetoxy-4,6-O-benzylidene-3-deoxy-D-erythro-hex-2-enono-1,5-lactone , 7) was synthesized and treated with tin(IV) chloride affording 3-acetoxy-6-chloromethyl-2-pyrone (8) as main product. The 2-pyrone derivatives 3 and 4 are convenient precursors for the synthesis of 5-hydroxynorvaline (12) and (2S,4R,5R)-4,5,6-trihydroxynorleucine (14), respectively. The latter was prepared by diastereoselective hydrogenation of 4, followed by deprotection.
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