Polystyrene-Based Deblocking-Scavenging Agents for the 9-Fluorenylmethyloxycarbonyl Amino-Protecting Group

Article abstract of DOI:10.1021/jo00153a008

Piperazino- and piperidino-functionalized polystyrenes have been examined as deblocking-scavenging agents for the 9-fluorenylmethyloxycarbonyl (Fmoc) amino-protecting group.Both commercial and synthesized polystyrenes have been used as supports.In order to introduce the active functional groups, (chloromethyl)polystyrene 2 was treated with tert-butyl piperazine-1-carboxylate followed by acidic deblocking (HCl/dioxane) or, alternatively, was directly aminated by means of 10 molar excess of piperazine or 1,3-bis(4-piperidino)propane.Compounds 7-9 were examined as cross-linking agents in the preparation of appropriate reagents.Most suitable were reagents prepared from commercial macroreticular resins (XE-305) or those cross-linked via DVT (8).Proof that the DBF liberated in the deblocking prozess was scavenged (partially) by the active secondary amine reagents 4 came from (a) a study of the successful regeneration of an active agent from 5 by treatment with alkali (H2O-dioxane) and (b) liberation of 9-methylfluorene from 5 by hydrogenation (NH4OCHO/Pd-C).