H. Reinhard et R. Brossmer, CHAIN LENGTHENING OF 1-DEOXY-1-NITROAIDIT OLS BY NITRILE OXIDE CYCLOADDITION - SYNTHESIS OF 4-N-SUBSTITUTED 3,4-DIDEOXY-2-ULOSONIC ACIDS, Tetrahedron, 54(18), 1998, pp. 4539-4560
Treatment of protected nitroalditols 1a or 2 with silylenolpyruvate (3
) or methyl acrylate leads via nitrile oxide cycloadditon to cycle-tau
tomers of oximes, 5 or 4, respectively 4,5-dihydro-isoxazole 6. N-Acet
yl-4-deoxy-4-(E/Z)-hydroxyimino-neuraminic acid (7) is obtained by dep
rotection of 4. Hydrogenation of 7 yields N-acetyl-4-amino-4-deoxy-neu
raminic acid (9) and pentahydroxy-nononic acids 12a,b. The synthesis i
s useful for the chain extension of protected nitroalditols 13a and 20
a, to give the corresponding oximes 15 and 22. This work provides a ge
neral method for the extension of sugar chains by three C-atoms and th
us a novel synthesis of cr-keto acids containing an oxime and amino fu
nction. (C) 1998 Elsevier Science Ltd. All rights reserved.