Synlett 2005(4): 595-598  
DOI: 10.1055/s-2005-863711
LETTER
© Georg Thieme Verlag Stuttgart · New York

Reactivity of PNA Thioesters in Chemical Ligation Reactions

Martijn C. de Koning, Matthijs van der Knaap, Lene Petersen, Hans van den Elst, Gijsbert A. van der Marel, Mark Overhand, Dmitri V. Filippov*
Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
Fax: +31(71)5274307; e-Mail: filippov@chem.leidenuniv.nl;
Further Information

Publication History

Received 22 November 2004
Publication Date:
22 February 2005 (online)

Abstract

The ligation rate and efficiency of PNA thioesters in the reaction with the pentapeptide CRYNK has been determined and proved to be substantially lower in comparison with the corresponding C-terminal glycine thioester.

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MS: m/z found (calculated) for:
Compound 6: [M + H+]: 1340.9 (1340.5), [M + 2 H+]: 670.9 (670.8).
Compound 7: [M + H+]:1283.6 (1283.5), [M + 2 H+]: 642.6 (642.3).
Compound 8: [M + H+]: 1308.5 (1308.3), [M + 2 H+]: 655.2 (654.7).
Compound 10: [M + H+]: 1847.1 (1846.2), [M + 2 H+]: 923.9 (923.6), [M + 3 H+]: 616.2 (616.1).
Compound 11: [M + H+]: 1788.9 (1788.8), [M + 2 H+]: 895.2 (894.9).
Compound 12: [M + H+]: 1815.2 (1814.8), [M + 2 H+]: 907.8 (907.9), [M + 3 H+]: 605.7 (605.6).

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On the basis of similar studies to assess the ligation efficiency of amino acid thioesters (see ref. 9) the pentapeptide CRANK was initially used. However, it proved to be impossible to resolve the PNA-conjugate of this peptide and the starting PNA thioester on RP-HPLC column.