SKEW-BOAT CONFORMATIONS FOR 2 SUGAR-DERIVED 5,6-DIHYDROPYRAN-2-ONES

The structures for two sugar-derived 5,6-dihydropyran-2-ones were dete rmined: bis-benzoyloxy-6-methyl-5,6-dihydro-2H-pyran-2-one (1), C20H16 O6, P2(1)2(1)2(1), a = 27.610(9), b = 10.734(4), c = 5.972 (2) angstro m, Z = 4, R = 0.033, R(w) = 0.037, and (5S)-3,5-bisbenzoyloxy-5.6-dihy dro-2H-pyran-2-one (2), C19H14O6, P2(1), a = 15.93 (1), b = 8.150 (5), c = 6.238 (5), beta = 99.43 (5)degrees, z = 2, R = 0.096, R(w) = 0.09 6. They adopt skew-boat (SB) solid-state conformations of the pyranoid ring, such that C-6, and, to a lesser degree, the ring oxygen lie abo ve a plane made up of C-(2) - C-(3) - C-(4) - C-(5).