β-Elimination in aldonolactones. the conversion of l-rhamnono-1-5-lactone into 3-benzoyloxy-6-methylpyran-2-one

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Benzoylation of l-rhamnono-1,5-lactone ( 1) for 90 min at room temperature afforded 2,3,4-tri- O-benzoyl- l-rhamnono-I,5-Iactone ( 2). When an excess of benzoyl chloride and pyridine was used for 20 h, with subsequent sublimation of benzoic acid from the mixture at 120° in vacua, a double elimination took place and 3-benzoyloxy-6-methylpyran-2-one ( 4) was isolated as the main product. The conversion of 1, 2, and 2,4.-di- O-benzoyl-3,6-dideoxy- l- erythro-hex-2-enono-l,5-lactone ( 3) into the pyran-one derivative 4 under different conditions was monitored chromatographically.