The synthesis of 5-amino-v-triazolo[4,5-b] pyridin-7-one (l-deaza-8-azaguanine) and 5-amino-3-(β-D-ribofuranosyl)-v-triazolo[4,5-b] pyridin-7-one (1-deaza-8-azaguanosine)

The synthesis of l-deaza-8-azaguanine has been accomplished via a facile route from pyridine precursors. The site of rihosylation and anomeric configuration of l-deaza-8-azaguanosine and several closely related derivatives was accomplished by cmr and pmr, respectively.     

Synthesis of certain 3,5,7-disubstituted pyrazolo[3,4-e][1,3]oxazines. Derivatives of a new heterocyclic ring system

The synthesis of several 3,5,7-trisubstituted pyrazolo[3,4-e][1,3]oxazines by ring annulation of the appropriately substituted pyrazoles is described.     

Intersecting M-branes

We present the magnetic duals of Güven's electric-type solutions of D = 11 supergravity preserving 1/4 or 1/8 of the D = 11 supersymmetry. We interpret the electric solutions as n orthogonal intersecting membranes and the magnetic solutions as n orthogonal intersecting 5-branes, with n = 2, 3; these cases obey the general rule that p-branes can self-intersect on (p − 2)-branes. On reduction to D = 4 these solutions become electric or magnetic dilaton black holes with dilaton coupling constant a = 1 (for n = 2) or (for n = 3). We also discuss the reduction to D = 10.     

Stability at a local maximum in higher dimensional anti-deSitter space and applications to supergravity

The stability of anti-deSitter background solutions of gravity/scalar systems with respect to small fluetuations of the scalar fields is analyzed. As in the four dimensional case, one finds stability even about a local maximum provided that the effective scalar field masses are not “too tachyonic,” and for sufficiently low mass there are two possible boundary conditions that allow a well-defined and conserved energy. Unlike the d = 4 case only one boundary condition is applicable to the known gauged supergravity theories in d = 5 and d = 7. For d = 7 the stability criterion is satisfied while for d = 5 stability is marginal.     

A chemical synthesis of the nucleoside 1-methylpseudouridine

A facile chemical synthesis of 1-methylpseudouridine has been accomplished by direct methylation of pseudouridine.