Synthesis of homologous peptides using fragment condensation: analogs of an HIV proteinase substrate.

Two protected peptides Boc-Val-Ser(Bzl)-Gln-Asn-Tyr(BrZ)OH and Boc-Val-Ser(Bzl)-Gln-Asn-Tyr(BrZ)-ProOH were synthesized on a resin substituted by 9-(hydroxymethyl)-2-fluoreneacetic acid. After cleavage with piperidine/DMF, desalting, and activation, these peptides were used for the synthesis of 11 analogs of an HIV proteinase nonapeptide substrate Val-Ser-Gln-Asn-Tyr-Pro-Ile-Val-Gln-NH2 using fragment condensation in solid phase. The fragment condensation was made in an ultrasonic bath. Using only 2 equivalents of the activated peptide in a DMF solution, this reaction was complete in 2 h. All nonapeptides were assayed as substrates for HIV-1 and HIV-2 proteinases.