This invention relates to compounds of the formula: ##STR1## wherein R is an electron withdrawing group; R.sub.1 is H or COZ; X.sub.1 and X.sub.2 are independently H, lower alkyl, aryl, aryl lower-alkyl or polystyrene or R and X.sub.1 taken together with the carbon atoms to which they are attached form a ring containing from 4 to 15 ring carbon atoms and may contain up to 2 heteroatoms, wherein the heteroatoms are O, S, or N; and Z is an amino acid residue, a peptide residue or a leaving group. The compounds of the present invention are adaptable as blocking or protecting groups for an amine composition useful in peptide synthesis. The present invention is also directed to a method of protecting an amino group of an organic molecule during a reaction which modifies a portion of the molecule other than the protected amino group.
Nitroxides (aminyl oxydes) - XL. ESR spectroscopic studies of β-sulfonyl substituted vinyl nitroxides and of a vinylogous nitronyl nitroxide
作者:Hans Günter Aurich、Klaus-Dieter Möbus
DOI:10.1016/s0040-4020(01)89107-9
日期:1989.1
Oxidation of hydroxylamines 1 affords the vinyl nitroxides 4 via 2 and 3. The vinylogous nitronyl nitroxide 5 is formed upon oxidation of 1h. Whereas the methyl group X in 4a is freely rotating, rotation of substituents X in 4b–d is restricted as is indicated by their ESR spectra. Particularly, the less hindered vinyl nitroxides 4e–g form spin adducts 6 or 7 with their precursor nitrones 3. 4b coexists