PDF(Pubmed)
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.
摘要：
一项非靶向代谢组学研究确定了人类尿液中四种潜在的肺癌诊断生物标志物。潜在的生物标志物之一是具有561+的m/z值的未鉴定特征。从人尿中分离出“561”，初步鉴定为27-nor-5β-胆甾烷-3α，7α,12α,使用1HNMR和质谱分析,具有未知C24,25立体化学的24,25戊醇葡糖苷酸。在先前的报告中，糖苷配基的C24,25立体化学，27-nor-5β-胆甾烷-3α，7α,12α,24,25戊醇，被发现是24S，25R通过丙酮化物-TMS衍生物的GC分析。制备真实样品,发现其立体化学与“561+”不相同。为了确定C24,25立体化学，27-nor-5β-胆甾烷-3α的四种C24，C25非对映异构醇，7α,12α,由手性氨基酸制备24,25戊醇。使用LCMS方法，“561+”糖苷配基的C24、C25立体化学被确定为24R，25S.手里拿着正确的aglycone，它与葡萄糖醛酸偶联完成了首次报道的27-nor-5β-胆甾烷-3α的合成，7α,12α,24R,25S戊醇葡糖苷酸。氘标记27-nor-5β-胆甾烷-3α，7α,12α,24R,还合成了25S戊醇以用作MS定量的内标。
