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. 2000 Jan;89(1):108-14.
doi: 10.1002/(SICI)1520-6017(200001)89:1<108::AID-JPS11>3.0.CO;2-A.

Degradation of azaglycinamido residues in model tripeptides derived from goserelin

M A Hoitink  1 , J H Beijnen, A Bult, J M Damen, O A van der Houwen, J A Kruijtzer, M M Tibben, G Wiese, W J Underberg
Affiliations

Degradation of azaglycinamido residues in model tripeptides derived from goserelin

M A Hoitink et al. J Pharm Sci. 2000 Jan.

Abstract

Three model tripeptides, N-acetyl-Tyr-Pro-azaGly-NH(2) (NYPaG), Tyr-Pro-azaGly-NH(2) (YPaG), and Tyr-Pro-Gly-NH(2)(YPG), were subjected to a systematic degradation study to get information about the degradation of the azaglycinamido residue. The degradation products were characterized with LC-MS. Main degradation products of NYPaG possess partially or totally eliminated azaglycinamido residues, while YPaG and YPG are exhibit cyclo(Tyr-Pro) formation, a diketopiperazine. The influence of the pH on the degradation rate constant k(obs) was investigated for NYPaG and YPaG in the pH range 0.4-11. An U-shaped profile with an inflexion around pH 9 was found for NYPaG while the degradation rate of YPaG was independent of the pH. NYPaG apparently was subject to proton-, solvent-, and hydroxyl-catalyzed degradation reactions whereas YPaG only underwent solvent-catalyzed reactions. Some influence of acetate and phosphate ions on k(obs) was found for YPaG. Arrhenius plots of NYPaG and YPaG were found to be linear.

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