Monitoring the reaction process of Fmoc-D-Ala-OH in solid-phase synthesis of peptides with near infrared spectroscopy

Solid phase peptide synthesis (SPPS) has received increasing attention from research laboratories and industry, and a variety of peptides have been successfully constructed in recent years. In this paper, near-infrared spectroscopy was applied to monitor SPPS process, and an analytical model of Fmoc-D-Ala-OH in SPPS solution was established. With the established model the Fmoc-D-Ala-OH content could be predicted rapidly at any time during the reaction. With a help of chemometric method of sampling error profile analysis (SEPA), some pretreatment methods were carefully compared, and the partial least squares method was used to build a model between NIR spectrum and Fmoc-D-Ala-OH content measured by high performance liquid chromatography (HPLC). The results showed that the model had a satisfactory performance, the determination coefficient, root mean square error of the calibration set were 0.9677 and 0.9284 mg/mL, respectively, and the determination coefficient, root mean square error of the prediction set were 0.9561, 1.1208 mg/mL, respectively. These results clearly showed that the model had a good predictive ability. Therefore, it had great potential in the monitoring of SPPS in pharmaceutical production.