Patent ID: 7696311

Claim:
A method of obtaining a peptide, comprising steps of: a. synthesizing a peptide intermediate having one or more side chain protecting groups, wherein the peptide intermediate can be used for synthesis of enfuvirtide and is selected from the group consisting of YTSLIHSL (SEQ ID NO:2), YTSLIHSLIEESQNQ (SEQ ID NO:3), YTSLIHSLIEESQNQQ (SEQ ID NO:4), YTSLIHSLIEESQNQQEK (SEQ ID NO:5), IEESQNQ (SEQ ID NO:6), IEESQNQQ (SEQ ID NO:7), QEKNEQELLELDKWASLWNW (SEQ ID NO:8), QEKNEQELLELDKWASLWNWF (SEQ ID NO:9), EKNEQEL (SEQ ID NO: 10), EKNEQELLEL (SEQ ID NO: 11), EKNEQELLELDKWASLWNWF (SEQ ID NO: 12), NEQELLELDKWASLWNW (SEQ ID NO:13), NEQELLELDKWASLWNWF (SEQ ID NO: 14), LELDKWASLWNW (SEQ ID NO: 15), LELDKWASLWNWF (SEQ ID NO: 16), DKWASLWNW (SEQ ID NO: 17), DKWASLWNWF (SEQ ID NO: 18), and EKNEQELLELDKWASLWNW (SEQ ID NO:19); b. providing a solvent to the peptide intermediate to form a peptide intermediate composition; and c. providing a precipitating agent in an amount sufficient to precipitate the peptide intermediate from the peptide intermediate composition, wherein the precipitating agent comprises an alcohol having three or more carbon atoms.