B. Bernet, U. Piantini, A. Vasella
Sep 5, 1990
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0
Influential Citations
17
Citations
Journal
Carbohydrate Research
Abstract
Abstract The A-values of the acetamido and the acetoxy group were determined by low-temperature 1 H-n.m.r. spectroscopy. The limiting values for the relevant vicinal coupling constants of the newly prepared trans - ( 22 ) and cis -5-acetoxy-2-(1-hydroxy-1-methylethyl)tetrahydropyran ( 24 ) were obtained at room temperature. The attractive gauche effect of AcNH-3 and AcO-3 in piperidines, piperidinium trifluoroacetates, and tetrahydropyrans was investigated by 1 H-n.m.r. spectroscopy both at low temperature (integrals) and at room temperature (band widths and coupling constants). The results obtained at low temperature are more reliable. The position of the conformational equilibrium of N -(3-piperidyl)acetamide ( 11 ), N -(1-methyl-3-piperidyl)acetamide ( 12 ), and N -(tetrahydropyran-3-yl)acetamide ( 17 ) [but not of 3-acetoxy-1-methylpiperidine ( 8 ) and 3-acetoxytetrahydropyran ( 15 )] depends strongly upon the nature of the solvent and, in apolar solvents, upon the concentration.