Triflates cryptand

Ligand 131 contains both cryptate and crown ether binding units. It reacts with neodymium triflate to give a 1 1 cryptate [Nd c 131]3+ exhibiting NIR luminescence upon excitation at 355 nm. The lifetime of the Nd(4F3/2) level is 347 and 711 ns in methanol and methanol-, respectively, which translates to MeOH 0 using eq. (10b). When barium ions are added to a solution of this complex in acetonitrile, the intensity of the 1.06 pm emission band is reduced substantially, while the lifetime of the Nd(4F3/2) level remains unchanged at about 470 ns. The Ndm ion is therefore not displaced from the cryptand cavity, while its luminescence is modulated by the presence of the Ba2+ ions bound by the crown ether (Coldwell et al., 2006). 

The naturally occurring cryptand aplasmomycin (190) is one of a unique family of ionophore antibiotics, and several syntheses of the total structure, half structure and various abbreviated segments have been published. White et al. have now described a new approach to (190) which features a novel ring contraction based on the rearrangement of a-(acyloxy) acetates originally described by Chan et al. Thus, the key intermediate (191) was treated successively with lithium diisopropylamide and trimethylsilyl triflate leading to (192) which was ultimately converted to aplasmomycin. In Corey s recent... 

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