PHOSPHONYLATION BY A SPIROPHOSPHORANE: APPLICATION OF THE RIBOZYME CHEMISTRY IN THE BIOORGANIC SYNTHESIS

The phosphonylation by oxirane/phosphorous acid is characterized by formation of spirophosphorane, which provides the active intermediate in the reaction, β-hydroxyalkyl alkylene phosphite. Here, we demonstrate that a well-known and readily accessible spirophosphorane, 2λ⁵-2,2′spirobi[1,3,2-benzodioxaphosphole] can be used as convenient and effective phosphonylating agent in similar reaction. The easily detectable primary 3-phenylpropyl H-phosphonate, as well as 5′-O-tritylthymidyl, 4-N-benzoyl-5′-O-trityl-deoxycytidyl, 5′-O-trityl-deoxycytidyl, 6-N-benzoyl-5′-O-trityl- deoxyadenosyl 5′-O-trityluridyl, and 2′,3′-isopropylidene-uridyl H-phosphonates were prepared using a simple and straightforward procedure. Our results provide an interesting example of the potential and the limitations of a synthetic approach utilising reaction of leaving of diol system.     

High-spin structure of the neutron-rich 107,109 45Rh isotopes: the role of triaxiality

The ^107,109Rh nuclei have been produced as fission fragments following the fusion reaction ²⁸Si +¹⁷⁶Yb at 145 MeV bombarding energy and studied with the Eurogam2 array. In both nuclei three new rotational bands with the odd proton occupying the πg_9/2, πp_1/2 and π(g_7/2/d_5/2) sub-shells have been observed. In ¹⁰⁷Rh, two other bands involving strong M1 transitions have been identified at excitation energy larger than 2 MeV. They can be interpreted in terms of three quasiparticle excitations. In addition new structures consisting of four transitions, built on states located at low excitation energy (680 keV in ¹⁰⁷Rh and 642 keV in ¹⁰⁹Rh), point out the importance of triaxial deformation in these two isotopes. Received: 1 September 1999