Affiliation:
1. Chemistry and Chemical Synthesis Center, National Heart, Lung, and Blood Institute, National Institutes of Health, 9800 Medical Center Drive, Rockville, MD 20850, USA
2. AstraZeneca, 1 MedImmune Way, Gaithersburg, MD 20878, USA
3. Laboratory of Human Carcinogenesis, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
Abstract
An untargeted metabolomic study identified four potential lung cancer diagnostic biomarkers in human urine. One of the potential biomarkers was an unidentified feature possessing a m/z value of 561+. “561+” was isolated from human urine and tentatively identified as 27-nor-5β-cholestane-3α,7α,12α,24,25 pentol glucuronide with unknown C24,25 stereochemistry using 1H NMR and mass spectrometry. In a prior report, the C24,25 stereochemistry of the aglycone, 27-nor-5β-cholestane-3α,7α,12α,24,25 pentol, was found to be 24S,25R through GC analysis of the acetonide-TMS derivative. An authentic sample was prepared and found not to have the same stereochemistry as ”561+”. To identify the C24,25 stereochemistry, four C24,C25 diastereoisomeric alcohols of 27-nor-5β-cholestane-3α,7α,12α,24,25 pentol were prepared from chiral amino acids. Using an LCMS method, the C24,C25 stereochemistry of the “561+” aglycone was determined to be 24R,25S. With the correct aglycone in hand, it was coupled with glucuronic acid to complete the first reported synthesis of 27-nor-5β-cholestane-3α,7α,12α,24R,25S pentol glucuronide. Deuterium labeled 27-nor-5β-cholestane-3α,7α,12α,24R,25S pentol was also synthesized for use as an internal standard for MS quantitation.
Funder
Intramural Research Program of the NIH, NCI/CCR