When tetraglycine methyl ester is heated at 100° C a decrease in methoxyl content is observed, mainly after an induction period of about 200 hours. The reaction is virtually finished after 600 hours. Previous powdering of the ester crystals slightly reduces the induction period. The reaction product mainly consists of a mixture of tetraglycine, N-methyl-glycyl-triglycine (sarcosyl-triglycine) and N-dimethylglycyl-triglycine. When alanyl-triglycine methyl ester is heated at 100° C the induction period extends over several months.