Synthesis of 5,5,6,6-D4-L-lysine-aflatoxin Bl for use as a mass spectrometric internal standard

✍ Scribed by Peter F. Scholl; John D. Groopman

• Book ID: 102375078
• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: French
• Weight: 148 KB
• Volume: 47
• Category: Article
• ISSN: 0022-2135
• DOI: 10.1002/jlcr.867

✦ Synopsis

Abstract

Human exposure to the hepatocarcinogenic mycotoxin aflatoxin B~l~ results in modification of serum albumin lysine ε‐amino residues to form lysine‐aflatoxin adducts. A perdeuterated reference standard is now required to quantitatively measure this adduct in epidemiologic studies of liver cancer using isotopic dilution mass spectrometry. A convenient method for the preparation of D4‐L‐lysine‐AFB~l~ using commercially available 5,5,6,6‐D4‐l‐lysine is demonstrated for the first time. The application of two standard α‐amino protection methods is also reported that simplifies the production of natural isotopic abundance lysine‐AFB~l~ over the currently used method employing N~α~‐acetyl‐l‐lysine. t‐Boc‐N~α~‐lysine was used to prepare lysine‐AFB~l~; however, a preferred method for directing reaction of AFB~l~‐dialdehyde to the ε‐amino group of 5,5,6,6‐D4‐l‐lysine utilized cupric ions that were spontaneously removed during the reverse phase HPLC purification of D4‐lysine‐AFB~l~ using 1% HOAc. This strategy eliminates the need to otherwise synthesize and purify t‐Boc‐N~α~‐ or N~α~‐acetyl‐5,5,6,6‐D4‐lysine and then TFA or enzymatically deprotect overnight to obtain the target compound. Copyright © 2004 John Wiley & Sons, Ltd.