Synthesis and structural study of 5-nitro-6-(penta-O-acetylpentitol-1-yl)norbornenes |
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Authors: | E Roman Galan Derek J Hodgson Yoshinobu Yokomori Ernest L Eliel and M Bueno Martinez Juan A Serrano Blazquez |
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Institution: | William R. Kenan, Jr. Laboratories of Chemistry, The University of North Carolina, Chapel Hill, NC 27514 U.S.A. Departamento de Química Orgánica, Facultad de Ciencias, Universidad de Extremadura, 06071-Badajoz España |
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Abstract: | Uncatalyzed reaction between cyclopentadiene and (E)-3,4,5,6,7-pentaacetoxy-1-nitrohept-1-enes having the
-manno,
-galacto, and
-gluco configurations at C-3—C-7 led, in each case, to the four stereoisomeric 5-nitro-6-(1,2,3,4,5-penta-O-acetylpentitol-1-yl)bicyclo2.2.1]hept-2-enes. Face selectivity is discussed in terms of the sugar-chain configuration. The structures assigned the adducts are based on their n.m.r. spectra, and, in the case of the
-manno compounds, on X-ray data. Also described are the 13C-n.m.r. spectra of the starting nitroalkenes. The crystal structures of (5S,6S)1,2,3,4,5-penta-O-acetyl-1-C-(5-exo-nitrobicyclo2.2.1]hept-2-en-6-endo-yl-
-manno-pentitol (3a) and (5S,6S)1,2,3,4,5-penta-O-acetyl-1-C-(5-endo-nitrobicyclo2.2.1]hept-2-en-6-exo-yl-
-manno-pentitol (5a) were determined from three-dimensional, X-ray data. Crystals of 3a are monoclinic, space group P21, with two molecules in a cell of dimensions a = 9.054(3), b = 15.580(11), c = 10.138(4) Å, β = 116.27(3)°. The structure was refined to an R-factor of 0.050 on the basis of 1485 observations. Crystals of 5a are triclinic, space group P1, with one molecule in a cell of dimensions a = 8.680(4), b = 9.760(4), c = 8.695(7) Å, = 98.69(5), β = 103.13(5), γ = 112.09(3)°. The structure was refined to an R-factor of 0.074 based on 970 observations. |
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