Exploring Solution-Phase Cyclization and Sulfamyl Safety-Catch Resin Strategies for the Total Synthesis of the Marine Antimicrobial Cyclic Tetrapeptide Cyclo(GSPE)
We designed and synthesized a series of novel hybrid histone deacetylase inhibitors based on conjugation of benzamide-type inhibitors with either linear or cyclic peptides. Linear tetrapeptides (compounds 13 and 14), cyclic tetrapeptides (compounds 1 and 11), and heptanediamide-peptide conjugates (compounds 10, 12, 15 and 16) were synthesized through on-resin solid-phase peptide synthesis (SPPS). All compounds were found to be moderate HDAC1 and HDAC3 inhibitors, with IC(50) values ranging from 1.3 microM to 532 microM. Interestingly, compound 15 showed 19-fold selectivity for HDAC3 versus HDAC1.