Structurally New Macrocycles from the Resorcinol-Aldehyde Condensation. Configurational and Conformational Analyses by Means of Dynamic NMR, NOE, and T1 Experiments

Article abstract of DOI:10.1021/jo00258a015

The acid-catalyzed condensation of resorcinol with heptanal or dodecanal followed by acetylation produces three stereoisomeric tetrameric macrocycles.The product distribution is controlled by the relative solubilities of the stereoisomeric octols in the reaction medium.These isomers comprise the previously described boat conformation (C_2υ symmetry) and chair conformation (C_2h symmetry) plus a new one with a diamond-like conformation (C_s symmetry).The corresponding relative configurations of the alkyl substituents, determined from NOE enhancements and NMR spectra, are all-cis, cis-trans-trans, and cis-trans-cis.In all three isomers, the alkyl substituents are in the less hindered axial position.The thermodynamically more stable boat octols can be obtained selectively in high yields (50-80percent) by heating the crude initial condensation mixtures at reflux for 4 h.