Synthesis of Benzophenone-Containing Analogues of Phosphatidylcholine

Abstract

As part of a collaborative study of cellular efflux of cholesterol and phospholipids, photoactivable analogues 4-8 of phosphatidylcholine (PC) having benzophenone groups in the choline moiety and at the end of the C2 and C1 alkyl chains have been synthesized. The efficient preparation via Suzuki coupling of the appropriate long-chain benzophenone-containing carboxylic acid and alcohol and their incorporation by adaptation of known approaches into the acyl- and ether-linked PC analogues 6-8 are described. Development of a method for radiolabeling these PC analogues, via hydrogenation of a double bond in modified side chains, is also described.

Preparation of isotopically labelled benzophenone-containing lipid analogues

“…This approach was initially explored with the 2:1 mixture of monobromo 9 and dibromo 10 produced by treatment of ester 11 2 with 1.5 equivalents of NBS in CCl 4 in the presence of benzoyl peroxide (Scheme 2), since we were ultimately interested in radiolabelling phosphatidylcholine analogues containing acid 2 esterified in the C1 or C2 acyl chain. 2 When the H NMR spectrum of the product showed peaks at d 2.69 and 2.46, indicating clearly the formation of a mixture of 12 and 13. This conclusion was confirmed by comparison of the 13 C NMR spectra of 12 plus 13 vs 11, which showed that the singlets at d 36.2 and 31.4 in 11, had, in 12 plus 13, essentially disappeared and diminished in intensity, respectively.…”

“…We have been preparing benzophenone-containing analogues of sterols 1 and phospholipids 2 for use as photoaffinity labelling agents in studies of cellular cholesterol efflux and HDL formation. [3][4][5] In particular, the cholesterol analogue 1, known as FCBP, 3 and the fatty acid analogue 2 ( Figure 1), 2 were required in radioactive form for use as biochemical research tools.…”

“…[3][4][5] In particular, the cholesterol analogue 1, known as FCBP, 3 and the fatty acid analogue 2 ( Figure 1), 2 were required in radioactive form for use as biochemical research tools. This has been accomplished to date by commercial catalytic tritiation of the brominated i-steroid derivative 3 1 and unsaturated acid 4 2 , respectively.…”

Proteome-wide detection of phospholipid–protein interactions in mitochondria by photocrosslinking and click chemistry

“…Recently, the syntheses of benzophenone-containing PC analogues and of benzophenone-containing cholesterol surrogates have been reported. 43,44 The benzophenone-derivatized sterols were shown to compete with cholesterol for apolipoprotein A-I-induced cellular efflux. 44 3-Trifluoromethyl-3-phenyl diazirines (TPD) generate carbenes upon UV light exposure that have a life time in the order of nanoseconds.…”

Synthesis of Trifunctional Phosphatidylserine Probes for Identification of Lipid‐Binding Proteins

“…Therefore, photoaffinity tagging by these PS lipid probes may be performed on intact, living cells as well as with fractionated cell lysates, followed by in-gel readout of the labeled fraction by using azide-alkyne cycloaddition with a fluorophore azide. To date, there have been relatively few phosphatidylserine lipid syntheses reported, [12][13][14][15][16] and while the general synthesis and application of lipid photoaffinity probes to identify biological partners has been well established, [17][18][19][20][21][22][23][24][25][26][27][28][29][30] none of these prior efforts are focused on the use of PS lipid mimics as affinity capture reagents for PS binding partners. [26] Photoaffinity probes based on PS lipids have been previously reported by using azido-photoactivated cross-linking prepared through enzyme-catalyzed choline-serine headgroup exchange.…”