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Synlett 2001; 2001(10): 1519-1522
DOI: 10.1055/s-2001-17457
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Directing the Regioselectivity of the Alkylation of Pyroglutamate Carbamates by Formation of a Stable Counter-ion Complex

Christian V. Stevens* , Thomas Rammeloo, Norbert De Kimpe
  • *Department of Organic Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Coupure links 653, 9000 Gent, Belgium; E-mail: Chris.Stevens@rug.ac.be
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Publication Date:
27 September 2001 (online)

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The alkylation of benzyl N-Boc pyroglutamate was carried out using chloroformates in order to introduce an activating group at the 4-position. Deprotonation with three equivalents of LiHMDS followed by alkylation with different electrophiles lead to 2-alkylated pyroglutamates. The directing effect of the alkylation to the 2-position can be accounted for by the formation of a counterion complex.

pyroglutamate - alkylation - lithium complex - carbamates - regioselectivity