By employing a series of peptide bond forming reactions followed by a 2,4,5-trichlorophenol active ester promoted cyclization the synthesis of cyclo-[L-Val-L-Leu-L-Pro-(R and S)-(gln)Thz-(gly)Thz] (2) was accomplished. Neither of the diastereomers was identical with the Indian Ocean sea hare cell growth inhibitory constituent dolastatin 3. However, the mass spectra of the synthetic cyclic pentapeptides (2) closely approximated that of the natural product, suggesting a close structural relationship. The El mass spectral fragmentation of cyclic peptides 2 and of two other structurally related cyclic pentapeptides was discussed.
ASJC Scopus subject areas
- Organic Chemistry