Diketopiperazine formation from the N-terminal residues of a peptide c
hain is accelerated by aprotic dipolar protophobic solvents and cataly
zed in organic solvents by alkylammonium carboxylate salts. The t(1/2)
for the first-order reaction of H-Ala-Pro-NH2 . TFA falls from 20 d i
n methanol to 3.6 min in acetonitrile containing 0.02 mol dm(-3) triet
hylammonium acetate; for H-Ala-Ala-NH2 . TFA in the same reaction medi
a t(1/2) falls from an unmeasurably long time to 1.3 d. (C) 1998 Elsev
ier Science Inc.