ChemInform Abstract: CYCLOADDITION WITH UNSATURATED CARBOHYDRATES. II. SYNTHESIS AND STRUCTURE OF 2,3‐DIDEOXY‐4′,5′‐DIHYDRO‐α‐D‐MANNO‐HEXOPYRANOSIDO(2,3‐D)ISOXAZOLE

Gnichtel, Horst; Autenrieth, Leonore; Luger, Peter; Vangehr, Kristina

doi:10.1002/chin.198239357

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“…The absence in each case of discernible coupling between the anomeric proton [H( l)] in the dipolarophile-derived portion of the adduct and the adjacent isoxazoline ring proton [H (2)] is consistent with the indicated trans-stereochemistry. 7 The reaction thus appears to be totally face selective with the nitrile oxide approaching the alkene, as expected, from the less hindered side anti to the C(1) and C(4) subtituents. Isoxazoline (4) was deacetylateds to (6) and then subjected to reductive hydrolysis9 (Pd/HZ or Raney Ni; boric acid/ Received, 3rd May 1988; Com.…”

Section: Synthesis Of C-disaccharides Using Nitrile Oxide Cycloadditimentioning

confidence: 79%

“…The xylose-mannose and xylose-glucose carbon-linked disaccharides 7 and 9 have been synthesised by a sequence in which the key steps are face selective 1,3-dipolar cycloaddition of xylose nitrile oxide (1) to the glucose-derived alkene (2) and reductive hydrolytic cleavage of the resulting 2-isoxazolines.…”

Section: Synthesis Of C-disaccharides Using Nitrile Oxide Cycloadditimentioning

confidence: 99%

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Synthesis of C-disaccharides using nitrile oxide cycloaddition chemistry

Dawson¹,

Johnson²,

Paton³

et al. 1988

J. Chem. Soc., Chem. Commun.

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The xylose-mannose and xylose-glucose carbon-linked disaccharides 7 and 9 have been synthesised by a sequence in which the key steps are face selective 1,3-dipolar cycloaddition of xylose nitrile oxide (1) to the glucose-derived alkene (2) and reductive hydrolytic cleavage of the resulting 2-isoxazolines.The synthesis of carbon-carbon linked disaccharides (C-disaccharides) is the subject of widespread current interest.1 In order to develop a general route which would provide pyranose C-disaccharides with control of both position and stereochemistry of the interunit linkage we have made use of nitrile oxide cycloaddition chemistry.2Our synthetic approach is based on cycloaddition of a sugar nitrile oxide to a sugar alkene and reductive hydrolytic cleavage of the resulting 2-isoxazoline (Scheme l ) . t To test the method we selected the P-D-xylose nitrile oxide (1) and the D-glucose-derived alkene (2)3 as representative 1,3-dipole and 1-4,5-Dihydroisoxazoles. dipolarophile respectively. The nitrile oxide was generated in situ in the presence of the alkene by a modification of the Mukaiyama4 procedure involving a dehydration of nitromethylxylose (3).5 Slow addition of a solution of precursor (3) to an excess of the alkene ensures a low concentration of the nitrile oxide thus minimising the competing dimerisation to furazan N-oxide.6 The use of tolylene di-isocyanate (rather than phenyl isocyanate) as dehydrating agent, and quenching the reaction with 1,2-diaminoethane, facilitates isolation of the cycloadducts.Only two, (4) and (5), of the four possible isoxazolines were detected by t.1.c. and 13C n.m.r. spectroscopy and were isolated as a ca. 1 : 1 mixture in a combined yield of 66%. The isomers were separated by chromatography and characterised

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Section: Synthesis Of C-disaccharides Using Nitrile Oxide Cycloadditimentioning

confidence: 79%

Section: Synthesis Of C-disaccharides Using Nitrile Oxide Cycloadditimentioning

confidence: 99%