Determination of protonation constants of some fluorinated polyamines by means of ~(13)C NMR data processed by the new computer program HypNMR2000. Protonation sequence in polyamines

摘要

The pK_a values of 6-fluoro-4,8-diazadodecane-1,12-diamine (6-fluorospermine) (1), 6,6-difluoro-4,8-diazadodecane-1,12-diamine (6,6-difluorospermine) (2), 6-fluoro-4-azaoctane-1,8-diamine (6-fluorospermidine) (3) and 6,6-difluoro-4-azaoctane-1,8-diamine (6,6-difluorospermidine) (4) in D_2O solution have been determined at 40 ℃ from ~(13)C NMR chemical shifts data using the new computer program HypNMR2000. The enthalpies of protonation of compounds 1-4 and the parent amines spermine (5) and spermidine (6) have been determined from microcalorimetric titration data. The values of △H°were used to derive basicity constants relative to 25 ℃. The NMR data have been analysed by two different methods to obtain information on the protonation sequence in the polyamines 1-5. The protonation sequence for spermine is related to its biological activity.