Amongthe methods for racemization testing in peptide synthesis, the GLCmethod is a simple one and the most practicable, especially when a packed column is used. In this method Tfa-Pro-X-OH (X=amino acids) is coupled with H-Val-Pro-OMe, the resulting Tfa-tetrapeptide-OMe is separated by GLC, and the degree of recemization is estimated from the ratio of the peaks separated to the diastereoisomers ldll and llll.1 2) The Tfa-Pro-X-OH used in this method has been prepared in several ways: for example, Tfa-Pro-Val-OH was prepared via Tfa-Pro-Val-O'Bu, which was obtained by direct condensation1 2' of both the amino acid derivatives or by replacement of Z-with the Tfa group from Z-Pro-Val-OlBu.2) It has also been prepared from Z-Pro-Val-OMe by saponification and subsequent replacement of Z-with the Tfa group.3) These methods were, however, fairly laborious in starting from amino acids. In this paper, we report a simpler procedure for preparing such compounds, Tfa-Pro-OH being coupled with H-X-OBzl to give Tfa-Pro-X-OBzl,
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