Stereochemical effects in some acronycine derivatives

The stereochemical effects of 18 natural and synthetic 1,2-dihydro-1,2-disu bstituted acronycine derivatives are reported. The conformation of the pyra n D ring was determined by using J couplings and NOEs derived from 1D H-1 a nd D-2 NOESY spectra and molecular mechanics calculations. In the case of t he 1-hydroxy derivatives the influence of the solvent, concentration and te mperature on the H-1 chemical shifts suggests that aggregation phenomena ta ke place in solution through the formation of an intermolecular hydrogen bo nd. Aggregation in the gas phase was confirmed by electrospray ionization m ass Spectra. The assignment of the C-13 chemical shifts was made by 2D NMR techniques. A correlation between the relative stereochemistry at C(1) and C(2) on the D ring and the methyl group carbon chemical shifts was establis hed. Copyright (C) 1999 John Wiley & Sons, Ltd.