Preparation of analog 3c possessing Z-Abu in place of Aib-3 commenced with coupling of 13 to dipeptide 18 (Scheme 6). We suspect that steric hindrance is the primary reason for the low yields of this reaction. Exposure of the resulting tetrapeptide 19 to the Martin sulfurane afforded 3c. The poor yields that we encountered while synthesizing some of the analogs of 1 are indicative of limits in current methods for constructing hindered peptides containing AAs. While our concise routes enabled us to overcome these problems and generate sufficient quantities of the small target peptides 2 and 3, we plan to address these limitations in future studies.