The Major Isoxazoline Cycloadduct from Reaction of a Xylopyranosylnitrile Oxide with a Hex-5-enopyranoside

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.

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