Diazirines carbene mimics

It has been found that the catalytic activity of PKC is enhanced by a lipid component of the cell membrane, namely phosphatidylserine. This activity is further stimulated by sn-1,2-diacylglycerol. Oleic acid also activates the enzyme in the presence of 1,2-diacylglycerol, and thus it is presumed to mimic phosphatidylserine. In order to identify that modulating binding site for oleic acid on PKC, a photoaffinity analogue was devised. A carbene generating photophore, diazirine was placed in the apolar terminus of the unsaturated fatty acid ligand (30, Fig. 12). The synthesis and the photochemical activation properties were reported by Ruhmann and Wentrup [113]. 

With the intent to selectively derivatize CyD oligosaccharides,80 Abelt enlisted nitrogenous carbene precursors as labile guests.81 The involvement of supramolecular carbenes could be inferred based on intramolecular products stemming from 1,2-H shifts. Of course, 3//-diazirines that possess a-C-H bonds, like 3-methyl-3-phenyl-3//-diazirine (6) (Scheme 2), are susceptible to rearrangements in the excited state (RIES) that mimic the results of carbene 1,2-H shifts,82 e.g., 6 —>10 (Scheme 2). 

Diazirine 63 was photolyzed in various solvents and within CyDs. The solution results are summarized in Table 8. The conventional solvents were used to gauge whatever effects the CyD hosts had on carbene 64. Hydrocarbon solvents, like pentane ( -C5Hi2) and cyclohexane (c-C6H12), were used to mimic the inner cavities of CyDs, which are also nonpolar, hydrophobic environments. Tetrahydrofuran (THF) was employed because the cyclic ether resembles the D-Glcp monomer units of the CyDs. Moreover, since CyDs also possess many hydroxyl (O-H) groups, it seemed appropriate to perform control experiments in alcoholic solutions of diazirine 63. Finally, chloroform (CHC13) was used to assess the spin-state of carbene 64. 

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See also in sourсe #XX -- [ , , , , , ]

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