Deoxygenated and alkylated furanoses: Thorpe-Ingold effects on tautomeric equilibria and rates of anomerization.
2-Deoxy-D-glycero-tetrose, 3-deoxy-DL-glycero-tetrose, 3-deoxy-3,3-di-C-methyl-DL-glycero-tetrose, 3-C-methyl-DL-erythrose, 3-C-methyl-DL-threose, 2-deoxy-5-O-methyl-D-erythro-pentose and 3-deoxy-5-O-methyl-D-erythro-pentose have been prepared, in some cases with 13C-substitution at the anomeric carbon, and characterized by 1H-(300 and 620 MHz) and 13C-n.m.r. (75 MHz) spectroscopy. The proportions of cyclic (alpha and beta furanoses) and acyclic (aldehyde and hydrate) forms were determined in aqueous (2H2O) solution, and ring-opening (kopen) and ring-closing (kclose) rate constants were measured by 1H and 13C saturation-transfer n.m.r. spectroscopy at p2H 5.0 (acetate buffer) and 60 degrees. The degree of furanose ring substitution was found to significantly affect both the thermodynamics and kinetics of furanose anomerization. Increased substitution enhances the proportion of cyclic forms in solution by stimulating furanose kclose. In contrast, furanose kopen was less affected by the degree of substitution; however, kinetic studies of 2-deoxyfuranose anomerization implicate furanose ring conformation as a potential determinant of kopen.
Snyder
J R
JR
Department of Chemistry and Biochemistry, University of Notre Dame, IN 46556.
Serianni
A S
AS
D000478:Alkylation; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009005:Monosaccharides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry; D012996:Solutions; D013237:Stereoisomerism; D013816:Thermodynamics
D009005:Monosaccharides; D012996:Solutions; D010100:Oxygen