Isolation,structure determination,and biological activity of a novel alkaloid,perophoramidine, from the Philippine ascidian Perophora namei

Chemical investigation of the Philippine ascidian Perophora namei has resulted in the isolation of a novel polycyclic alkaloid, perophoramidine (1). The structure of 1 was determined by the interpretation of 1D/2D NMR and MS data. Dehalogenation of perophoramidine (1) by ammonium formate catalyzed transfer hydrogenation confirmed the type and number of halogen atoms present in 1.     

Reduction of iridium in solution

Iridium(IV) in solution may be reduced to metal via the intermediate Ir(I). Reduction of Ir(III) has not been detected. The current efficiency for metal deposition is low because: (1) The (IV)-(I) reduction is competing with the (IV) to (III) reduction, and hydrogen evolution in aqueous solution. (2) Ir(I) is very easily oxidised to (III), even by hydrogen. (3) Some iridium salts are not stable in the (IV) state (e.g. triaquotrichloroiridate in molar chloride).     

Classical dependence of polarization on potential energy surface in rotationally inelastic collisions

Quasiclassicol trajectory calculations have been performed for model potential energy surfaces to investigate polarization in (j,m_j) → (j',m_j) integral cross sections For j = 0, it was found that the occurrence of polarization requires an attractive well, and that it be in the collinear configuration Results for j≠ 0 are also presented.     

Outer approximation algorithm for nondifferentiable optimization problems

Omissions from the list of references of Ref. 1 are corrected.     

Optimal Control of Constrained Piecewise Affine Discrete-Time Systems

This paper makes two contributions; firstly, it provides a characterization of the solution of the optimal control problem for piecewise affine discrete-time systems with a quadratic cost function (the generally preferred option) and, secondly, provides a simple method (reverse transformation) for solving this and the previously solved &ell problem. The characterization is useful for on-line implementation.     

A quadratically convergent algorithm for solving infinite dimensional inequalities

Many design algorithms can be formulated as determining a set of parameters to satisfy conventional and infinite dimensional constraints. An algorithm, with quadratic rate of convergence, for solving such inequalities, is presented.Research supported by the United Kingdom Science Research Council and the National Science Foundation ECS-79-13148.     

Feasible directions algorithms for optimization problems with equality and inequality constraints

In this paper two algorithms, of the feasible-directions and dual feasible-directions type, are presented for optimization problems with equality and inequality constraints. An associated problem, having only inequality constraints, is defined, and shown to be equivalent to the original problem if a certain parameter is sufficiently large. The algorithms solve the associated problem, but incorporate a method for automatically increasing this parameter in order to ensure global convergence to a solution to the original problem. Any feasible directions algorithm can be similarly modified to enable it to handle equality constraints.Research sponsored by the US Army Research Office — Durham, Contract DAHCO4-73-C-0025 and the National Science Foundation Grant GK-37572.     

Reference Parameters for Protein Hydrogen Exchange Rates

The analysis of many hydrogen exchange (HX) experiments depends on knowledge of exchange rates expected for the unstructured protein under the same conditions. We present here some minor adjustments to previously calibrated values and a stringent test of their accuracy.

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