Concerning selectivity in the oxidation of peptides by dioxiranes. Further insight into the effect of carbamate protecting groups.
With use of methyl(trifluoromethyl)dioxirane (TFDO), the oxidation of some tripeptide esters protected at the N-terminus with carbamate or amide groups could be achieved efficiently under mild conditions with no loss of configuration at the chiral centers. Expanding on preliminary investigations, it is found that, while peptides protected with amide groups (PG = Ac-, Tfa-, Piv-) undergo exclusive hydroxylation at the side chain, their analogues bearing a carbamate group (PG = Cbz-, Moc-, Boc-, TcBoc-) give competitive and/or concurrent hydroxylation at the terminal N-H moiety. Valuable nitro derivatives are also formed as a result of oxidative deprotection of the carbamate group with excess dioxirane. A rationale is proposed to explain the dependence of the selectivity upon the nature of the protecting group.
Annese
Cosimo
C
Dipartimento Chimica, CNR-ICCOM, Università di Bari, v. Amendola 173, 70126 Bari, Italy.
D'Accolti
Lucia
L
De Zotti
Marta
M
Fusco
Caterina
C
Toniolo
Claudio
C
Williard
Paul G
PG
Curci
Ruggero
R
D002219:Carbamates / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D005027:Ethylene Oxide / Q000031:analogs & derivatives* / Q000737:chemistry; D006900:Hydroxylation; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D010084:Oxidation-Reduction; D010455:Peptides / Q000737:chemistry*
D002219:Carbamates; D004852:Epoxy Compounds; D009842:Oligopeptides; D010455:Peptides; C061799:dioxirane; C445840:methyl(trifluoromethyl)dioxirane; D005027:Ethylene Oxide