Department of Chemistry and Biochemistry, and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093-0358, USA.
J Nat Prod. 2009 Mar 27;72(3):353-9. doi: 10.1021/np800549n.
The configuration of leucettamol A (1), a known long-chain "two-headed" sphingolipid (dimeric sphingolipid) from the marine sponge Leucetta microrhaphis, was determined by conversion to an N,N',O,O'-tetrabenzoyl derivative, measurement of the exciton coupled circular dichroism spectrum (ECCD), and quantitative analysis by deconvolution of superposed exciton couplets. Contrary to the earlier assignment that claimed leucettamol A (1) was racemic, the CD approach unambiguously reveals the natural product is chiral and optically active and displays pseudo-C(2) symmetry. The configuration of each end of the chain has erythro stereochemistry with an absolute configuration of 2R,3S,28S,29R. We show that deconvolution ECCD reliably predicts erythro versus threo vicinal amino alcohols in all cases with greater sensitivity (<5 nmol) compared to (1)H NMR J-based methods and provides verification of optical purity and unequivocal elucidation of absolute configuration in this difficult class of natural products.
从海洋海绵 Leucetta microrhaphis 中分离得到的已知长链“双头”神经酰胺（二聚神经酰胺）leucettamol A（1）的构型通过转化为 N，N'，O，O'-四苯甲酰衍生物、测定外消旋圆二色性光谱（ECCD）以及通过重叠外消旋偶合峰的解卷积进行定量分析来确定。与先前声称 leucettamol A（1）是外消旋的分配相矛盾的是，CD 方法明确地表明天然产物是手性和光学活性的，并显示出拟 C（2）对称性。链两端的构型均具有赤型立体化学，绝对构型为 2R，3S，28S，29R。我们表明，与基于（1）H NMR J 的方法相比，解卷积 ECCD 可靠地预测了所有情况下赤型与 threo 邻氨基醇（灵敏度 <5 nmol），并提供了对光学纯度的验证以及在该困难类天然产物中绝对构型的明确阐明。
