Synthesis of potential purinoceptor antagonists: application of P1-tBU phosphazene base for alkylation of adenine in solution and on solid phase

Alkylation of adenine in solution and on solid phase was accelerated by phosphazene base P1-tBu compared to mineral bases. The reactions in solution afforded regioselectively the appropriate N9-alkylated adenines with high preparative yields while the reaction with polystyrene resin-bound N-bromoacetylated peptides gave three regioisomers (alkylated at the N9, N7, and N3 position of adenine) in a 4:2:1 molar ratio. Ten novel nonphosphate nucleotide analogues were tested in an ADP-induced platelet aggregation assay.     

High resolution optical spectra in vivo: Photoactive protochlorophyllide in etiolated leaves at 5 K

We describe here high-resolution spectra of etiolated leaves studied by means of selective monochromatic excitation of fluorescence as well as by hole-burning technique at liquid helium temperature. Up to now site selection spectroscopy has not been successfully applied to biologically active chromophores in vivo. Our results demonstrate that even in the presence of specific pigment-protein and pigment-pigment interactions very narrow purely electronic lines can be obtained in the optical spectra of biological systems.