Scheme 4. Installation of acyl chains and global deprotection of QS saponin linkage variants. Reagents and conditions (a) H2S, pyr, Et3N, 78–94%; (b) dodecanedioic acid monobenzyl ester, i-BuOCOCl, Et3N, THF, 0 °C, 4 h, then add appropriate amine from step a, 57–93%; (c) H2, Pd/C, 1 : 1 THF/EtOH, 4–16 h; (d) 3 : 1 TFA/H2O, 0 °C, 1 h, 33–82% yield (two steps).
