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organic compounds
The present structure determination of (5R)-5-(2,3-O-isopropylidene-1-O-methyl-α-Dlyxo-tetrafuranos-4-yl)-4,5-dihydroisoxazole, C22H31NO12, at 150 K, taken with the known absolute configurations of the starting alkene and the nitrile oxide precursor, establishes the configuration (R) of the new stereogenic centre C(5) in the title compound, the major cycloadduct. The five-membered 4,5-dihydroisoxazole ring adopts a mainly envelope conformation folded between O(5) and O(6), whereas the furanoside and dioxolane rings lie between twist and envelope. The xylopyranosyl ring adopts a near ideal chair conformation.