Thermal and photochemical epimerization/equilibration of carbohydrate cobaloximes

G. X. Yu, D. R. Tyler, Bruce Branchaud

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Epimeric carbohydrate alkyl cobaloximes 4:5, 9:10, and 12:13 can be equilibrated thermally or photochemically. In each case, one isomer is strongly favored: exo-3-deoxy-3-pyridyldimethylgly-oximatocobalt-1, 2:5,6-di-O-isopropylidene-α-D-glucofuranose 4 for the 4:5 epimer pair, exo-3-deoxy-3-pyridyldimethylglyoximatocobalt-5-O-carboxymethyl-1, 2-O-isopropylidene-α-D-xylofuranose 9 for the 9:10 epimer pair, and equatorial 1-deoxy-1-pyridyldimethylglyoximatocobalt-2,3,4, 6-tetra-O-benzyl-β-D-glucopyranose 12 for the 12:13 epimer pair. These data indicate that there is a strong facial preference for the coupling of py(dmgH)2Co· radicals with alkyl R· free radicals, with the preferred kinetic path leading to the more stable product.

Original languageEnglish (US)
Pages (from-to)5687-5691
Number of pages5
JournalJournal of Organic Chemistry
Volume66
Issue number17
DOIs
StatePublished - Aug 24 2001
Externally publishedYes

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Isomers
Free Radicals
Carbohydrates
Kinetics
cobaloxime
Hot Temperature
1,2-5,6-di-O-isopropylidene-D-glucofuranose
propylene

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Thermal and photochemical epimerization/equilibration of carbohydrate cobaloximes. / Yu, G. X.; Tyler, D. R.; Branchaud, Bruce.

In: Journal of Organic Chemistry, Vol. 66, No. 17, 24.08.2001, p. 5687-5691.

Research output: Contribution to journalArticle

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abstract = "Epimeric carbohydrate alkyl cobaloximes 4:5, 9:10, and 12:13 can be equilibrated thermally or photochemically. In each case, one isomer is strongly favored: exo-3-deoxy-3-pyridyldimethylgly-oximatocobalt-1, 2:5,6-di-O-isopropylidene-α-D-glucofuranose 4 for the 4:5 epimer pair, exo-3-deoxy-3-pyridyldimethylglyoximatocobalt-5-O-carboxymethyl-1, 2-O-isopropylidene-α-D-xylofuranose 9 for the 9:10 epimer pair, and equatorial 1-deoxy-1-pyridyldimethylglyoximatocobalt-2,3,4, 6-tetra-O-benzyl-β-D-glucopyranose 12 for the 12:13 epimer pair. These data indicate that there is a strong facial preference for the coupling of py(dmgH)2Co· radicals with alkyl R· free radicals, with the preferred kinetic path leading to the more stable product.",
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N2 - Epimeric carbohydrate alkyl cobaloximes 4:5, 9:10, and 12:13 can be equilibrated thermally or photochemically. In each case, one isomer is strongly favored: exo-3-deoxy-3-pyridyldimethylgly-oximatocobalt-1, 2:5,6-di-O-isopropylidene-α-D-glucofuranose 4 for the 4:5 epimer pair, exo-3-deoxy-3-pyridyldimethylglyoximatocobalt-5-O-carboxymethyl-1, 2-O-isopropylidene-α-D-xylofuranose 9 for the 9:10 epimer pair, and equatorial 1-deoxy-1-pyridyldimethylglyoximatocobalt-2,3,4, 6-tetra-O-benzyl-β-D-glucopyranose 12 for the 12:13 epimer pair. These data indicate that there is a strong facial preference for the coupling of py(dmgH)2Co· radicals with alkyl R· free radicals, with the preferred kinetic path leading to the more stable product.

AB - Epimeric carbohydrate alkyl cobaloximes 4:5, 9:10, and 12:13 can be equilibrated thermally or photochemically. In each case, one isomer is strongly favored: exo-3-deoxy-3-pyridyldimethylgly-oximatocobalt-1, 2:5,6-di-O-isopropylidene-α-D-glucofuranose 4 for the 4:5 epimer pair, exo-3-deoxy-3-pyridyldimethylglyoximatocobalt-5-O-carboxymethyl-1, 2-O-isopropylidene-α-D-xylofuranose 9 for the 9:10 epimer pair, and equatorial 1-deoxy-1-pyridyldimethylglyoximatocobalt-2,3,4, 6-tetra-O-benzyl-β-D-glucopyranose 12 for the 12:13 epimer pair. These data indicate that there is a strong facial preference for the coupling of py(dmgH)2Co· radicals with alkyl R· free radicals, with the preferred kinetic path leading to the more stable product.

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