P. Bailey, Gavin A. Crofts
May 26, 1992
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Influential Citations
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Citations
Journal
Tetrahedron Letters
Abstract
Several methods for the preparation of cyclo-(Lys-Lys-Gly)2 were compared. Cyclisation of linear hexapeptides of the type H-[Lys(Z)-Lys(Z)-Gly]2-X was most efficient using excess DPPA with the free amino acid (i.e. X = OH), but purification and scale-up were problematical. Much more efficient was cyclo-dimerisation of H-Lys(Z)-Lys(Z)-Gly-OPFP.TFA, using Cs2CO3 as the neutralising base; purification from this procedure was easy, and scale-up involved no loss of yield. The cyclo-dimerisation route proceeded in 38% overall yield from the tripeptide Boc-Lys(Z)-Lys(Z)-Gly-OMe, whereas the best yield via the linear pathway was 20.5% from the same tripeptide starting material.