Several partially acetylated aldopyranosyl chlorides with an unprotected hydroxyl group at C-2 have been synthesised and some have been oxidised with ruthenium tetraoxide. In this way, fully acetylated pyranosylulose chlorides having the α-D-arabino-hexo, α-D-lyxo-hexo, and β-L-erythro-pento structures have been prepared. Their rates of methanolysis have been determined. Key intermediates in the synthetic sequences were the per-O-acetyl-2-O-trichloroacetylglycopyranosyl chlorides, of which the α- and β-D-galacto, α- and β-L-arabino, and α and β-D-xylo compounds were hitherto unknown. The β-D-xylo derivative exists in the conformation in which all the ring substituents are axially disposed, whereas the α-L-arabino compound is a rare example of an acylated pentopyranosyl chloride that adopts, preponderantly, a chair conformation that places the halogen in an equatorial orientation. © 1973.
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