2- and 8-Functionalized 1,4,7,10-tetraoxaspiro [5.5] undecanes. Part 4. Conformational study by 1H and 13C NMR spectroscopy

Abstract

¹ H and ¹³C NMR spectra of new 1,4,7,10-tetraoxygenated spiroacetals 1, 2, 3 and 4, were analysed by using 1D and 2D methods. This allowed us to give a definite structural characterization of the E,E, Z,E and E,Z isomers obtained by a cyclodehydrative reaction carried out on a dihydroxyketone precursor, under thermodynamic control. The introduction of oxygen atoms in the 4 and 10 positions did not modify the structural features previously observed for 1,7-dioxygenated spiroacetals obtained from natural and synthetic sources.