Structural elucidation by 1D and 2D NMR of three isomers of a carotenoid lysophosphocholine and its synthetic precursors

✍ Scribed by Bente Jeanette Foss; Jostein Krane

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 248 KB
• Volume: 42
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1365

✦ Synopsis

Abstract

A carotenoic acid was used to obtain a long‐chain unsaturated lysophosphocholine. The carotenoid lysophosphocholine was synthesized by two methods. The first method resulted in mixtures of regioisomers for each step in the synthetic route. Homo‐ and heteronuclear 1D and 2D NMR methods were employed to elucidate the structures of the individual isomers and their intermediates. The pure regioisomer [1‐(β‐apo‐8^′^‐carotenoyl)‐2‐lyso‐glycero‐3‐phosphocholine] was obtained by a second method, but in low yield. The 1D ^1^H NMR subtraction spectrum of the mixture and the pure regioisomer was used to interpret the ^1^H shifts of the unsaturated acyl moieties. The ^1^H and ^13^C signals of the acyl chain show characteristic shifts depending on the positions of the choline and the acyl group attached to the glycerol backbone. Therefore, the unsaturated acyl chain signals have diagnostic values for the identification of isomers of unsaturated (lyso)phosphocholines. Chemical shifts and indirect coupling constants are reported for each of the major components of the mixtures. The methods used were 1D (^1^H, ^13^C and ^31^P) and 2D (H,H‐COSY, HMBC, HSQC and HETCOR) NMR. Copyright © 2004 John Wiley & Sons, Ltd.