Control of the chiral purity of N-Fmoc/Boc amino acid derivatives (N-PADs) used in the manufacturing of therapeutic peptides is an important material quality attribute to reduce the risk of undesired pharmacological and toxicological effects arising from related diastereomeric impurities in drug substances. In this study, chiral HPLC methods for 4 pairs of unnatural (Tic, Oic, Ala(thi) and Hyp) and 11 pairs of natural N-Fmoc amino acid derivatives (N-PADs) were developed and optimized on carbohydrate-based chiral stationary phases (CSPs) CHIRALPAK IA, IC and QNAX. Mobile phase solvent polarity played a major role in chiral recognition events using CSPs, among the other method parameters such as temperature, flow rate and mobile phase additives. CHIRALPAK IA, IC and QNAX were able to show chiral recognition for all the d and l enantiomers of 4 unnatural (Tic, Oic, Ala(thi) and Hyp) N-PADs, with better selectivity (1.32 < < 2.12) and resolution (2.9 < Rs < 7.7) towards the IC CSP. Natural N-PADs also showed better selectivity (1.18 < < 2.88) and resolution (2.2 < Rs < 12.5) on the IC CSP compared to the QNAX CSP (1.02 < < 1.59) and (1.6 < Rs < 6.0), respectively. Enantiomeric recognition of Phe N-PADs was higher towards CHIRALPAK IA (1.64 < < 2.67; 7.41 < Rs < 8.62) compared to CHIRALPAK IC and QNAX CSPs. Considering the trends of hydrophobicity (logP) of N-PADs and obtained separation factors (), chiral recognition especially on CHIRALPAK IC is primarily influenced by the hydrophobicity ( interactions) arising due to the protecting groups when analysed under similar mobile phase solvent mixtures and chromatographic conditions. The recognition events on QNAX can be due to ion exchange and dipoledipole interactions evident from lower retention times for both natural and unnatural N-PADs. These optimized methods were further validated as per ICH guidelines and sensitive in estimating undesired isomers (0.05%) in the presence of desired isomers.
Analytical Methods – Royal Society of Chemistry
Published: May 17, 2018
It’s your single place to instantly
discover and read the research
that matters to you.
Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.
All for just $49/month
Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly
Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.
Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.
Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.
All the latest content is available, no embargo periods.
“Hi guys, I cannot tell you how much I love this resource. Incredible. I really believe you've hit the nail on the head with this site in regards to solving the research-purchase issue.”Daniel C.
“Whoa! It’s like Spotify but for academic articles.”@Phil_Robichaud
“I must say, @deepdyve is a fabulous solution to the independent researcher's problem of #access to #information.”@deepthiw
“My last article couldn't be possible without the platform @deepdyve that makes journal papers cheaper.”@JoseServera