Sheppard designed polyacrylamide polymers for peptide synthesis as
it was expected that these polymers would more closely mimic the properties of the
peptide chains themselves and have greatly improved solvation properties in polar,
aprotic solvents (e.g. DMF, or N-methyl pyrrolidinone).
Sheppard also proposed the use of a new protection and linking strategy. The Merrifield approach
depended on a benzyl ester linkage and Boc protection. But a more mild protection/deprotection
were sought. The protecting group finally chosen was the fluorenylmethoxycarbonyl (Fmoc)
which can be removed by base (usually piperidine).