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2004
Peptides
U 0400
44- 216
Hexafluoroacetone as Protecting and Activating Reagent. A New Approach to
N-Glycosides. — ω-Carboxy-α-amino acids react with hexafluoroacetone to give exclusively five-membered lactones like (I), achieving protection of the α-amino and the
adjacent carboxy group in one step. The unprotected carboxy group of the lactones can
be activated by treatment with acid chlorides or TBTU. Acylation of (I) with the weak
nucleophile (II) occurs with excellent regioselectivity in the presence of the base NEM.
In the following step the lactone moiety reacts as an activated ester to produce N-glycosylated dipeptides on reaction with amino acid esters, cf. (III)→(V). Elongation of
the peptide backbone in N-terminal position is possible without the need of a deprotection step, cf. (V)—(VII), since cleavage of the lactone ring is accompanied with the
deprotection of the N-terminal amino group. Treatment of oxazolidinone (IIIa) with
DMAP initiates a fragmentation reaction. — (BOETTCHER, C.; SPENGLER, J.;
ESSAWY, S. A.; BURGER*, K.; Monatsh. Chem. 135 (2004) 7, 853-863;
Fachbereich Chem., Univ. Leipzig, D-04103 Leipzig, Germany; Eng.) —
H. Hoennerscheid
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