Piperidine → Divinylbenzene-styrene

(NaSO3-Fmoc)4-PBP-2, 10.1 mg, was prepared according to the procedure of Example 8. The protected peptide was dissolved in 0.20 mL DMF and 0.020 mL saturated NaHCO3 pH 8.7; 0.003 mL octyl isocyanate was added and stirred at RT to produce Compound 9P. Octyl isocyanate is commercially available, e.g., from Aldrich (Milwaukee, Wis.). After 45 min at RT 0.020 mL piperidine was added. After 40 min at RT the reaction mixture was diluted with 10 mL 20% CH3CN containing 0.014 mL H2SO4. Product was isolated on a 0.5 g styrene-divinylbenzene cartridge (EnviChrom-P®) using incrementally increasing concentrations of CH3CN about 0.05M in sodium sulfate at pH 2.3; product was eluted with 25% and 30% CH3CN. Product-containing fractions were pooled, solvent removed under vacuum, 2 mL 1.0 M ammonium acetate pH 5.0 buffer was added, pH adjusted to 5.0 by addition of ca. 0.6 mL 1.5 M NH4OH, and then diluted with an equal volume of MeOH. Product was isolated via CM-Sepharose® chromatography as described in Example 7. The product was further purified on a 0.5 g styrene-divinylbenzene cartridge as above but using eluents at pH 9.9 (0.10 M NH4OH-0.01 M (NH4)2SO4); product eluted with 30% CH3CN. Product-containing fractions were pooled, solvent removed under vacuum, and product was desalted and freeze dried using the procedure of Example 5. Yield: 2.7 mg of a white solid, C52H92N16O11. FABMS: calc. for C52H93N16O11, (M+H)+=1118.7. Found: 1119 (M+H)+, 1141 (M+Na)+, 1157 (M+K)+.