Stable isolated symmetrical anhydrides of N alpha-9-fluorenylmethyloxycarbonylamino acids in solid-phase peptide synthesis. Methionine-enkephalin synthesis as an example.

The synthesis and isolation of symmetrical anhydrides of N alpha-9-fluorenylmethyloxycarbonyl (Fmoc) amino acids using water soluble carbodiimide is described. These compounds were used in a solid phase peptide synthesis of methionine-enkephalin on a p-benzyloxybenzyl ester polystyrene 1% divinylbenzene resin support. Homogeneous free pentapeptide was obtained in 42% overall yield. The Fmoc amino acid symmetrical anhydrides were stable during prolonged storage (2 years of 0 degrees) and offer advantages over present "Fmoc solid phase" methods which use anhydrides formed in situ.