López Jordi F, Grimalt Joan O
Department of Environmental Chemistry, Institute of Chemical and Environmental Research (IIQAB-CSIC), Barcelona, Catalonia, Spain.
J Am Soc Mass Spectrom. 2006 May;17(5):710-20. doi: 10.1016/j.jasms.2006.01.015. Epub 2006 Mar 15.
The usefulness of n-propyl-, iso-propyl-, and cyclopropylamines for the location of double bonds positions in C37-C40 alkenones after formation of imino derivatives has been evaluated. Cyclopropylamine is the best reagent for its high reaction yields, GC retention time difference between derivatives and precursor compounds, and absence of generation of byproducts. The use of this C3 amine involves higher sensitivity and ease of application than previously reported C5 amines. Examination of a large group of alkenones from cultures of Emiliania huxleyi, water particles, and recent and ancient sediments with cyclopropylamine derivatization shows that, in all cases, the double bonds were located at the same carbon atom distance from the carbonyl group, and spaced in intervals of five methylene groups either from the carbonyl or between them, e.g., at sites 7, 14, 21, and 28. This result represents a correction from previous assumptions in which double-bond positions were situated by reference to the methyl end. 4,4-Dimethyloxazoline derivatization of hexatriacontenoates showed that these compounds have also their unsaturations with seven carbon atom spacing and counting by reference to the carboxyl group. The concurrence of both series of isomers in compounds of different oxygen functionalities indicates that the precursor haptophycean algal species have a major biosynthetic pathway leading to the formation of these lipids. The data presented in this work unify the structures of the known alkenones in the present and the recent past under a common metabolic pathway.
在形成亚氨基衍生物后，已评估了正丙胺、异丙胺和环丙胺在确定C37 - C40链烯酮中双键位置方面的用途。环丙胺是最佳试剂，因其反应产率高、衍生物与前体化合物之间的气相色谱保留时间差异以及无副产物生成。与先前报道的C5胺相比，使用这种C3胺具有更高的灵敏度和更易于应用。用环丙胺衍生化法检测来自赫氏颗石藻培养物、水体颗粒以及近代和古代沉积物中的大量链烯酮，结果表明，在所有情况下，双键均位于距羰基相同碳原子距离处，且与羰基之间或它们彼此之间以五个亚甲基为间隔，例如在第7、14、21和28位。这一结果修正了先前的假设，即双键位置是参照甲基端确定的。对三十六碳烯酸酯进行4,4 - 二甲基恶唑啉衍生化表明，这些化合物的不饱和度也是以七个碳原子为间隔并参照羧基进行计数的。不同氧官能团化合物中这两种异构体系列的同时存在表明，前体定鞭藻藻类物种具有导致这些脂质形成的主要生物合成途径。本研究中呈现的数据在一个共同的代谢途径下统一了当前和近期已知链烯酮的结构。
