A number of mycosamine equivalents were synthesized and utilized in glycosidation attempts with the amphoteronolide B derivative 9 (Scheme 16). Of those examined, most failed. However, the mycosamine derivatives 7 and 72 proved interesting in that both reacted with 9 under suitable conditions to give the coupled products in reasonable yields, but unfortunately with the undesired a-linkage (Scheme 16). A conceptually new approach that ultimately led to a successful solution to the problem was therefore developed. [Pg.444]

The vapor pressure, density and temperature practically do not change along the evaporation region in physieally realistic systems. The latter allows one to simplify the system of governing equations and reduce the problem to a successive solution of the shortened system of equations to determine the velocity, liquid pressure and gaseous phases as well as the interface shape in a heated capillary. [Pg.375]

The search for amounts to successive solution of three-point equations of the form (E - - r i2(j)w = F by the elimination method for every component of the vector w with the index account from a to a -b 1. One possible way of covering this is connected wdth the performance of the following algorithm ... [Pg.590]

If Caf ) = C is a lower triangle matrix and all the operators Caa are invertible, then the procedure of solving equations (42 ) can be reduced to successive solution of the equations... [Pg.620]

What has been done is to reduce this system to successive solution of simpler equations moving from a to o -f 1 ... [Pg.641]

If many atoms are bound together, for example in a crystal, their atomic orbitals overlap and form energy bands with a high density of states. Different bands may be separated by gaps of forbidden energy for electrons. The calculation of electron levels in the periodic potential of a crystal is a many-electron problem and requires several approximations for a successful solution. [Pg.150]

Throughout our discussions we have emphasized the application of thermodynamic methods to specific problems. Successful solutions of such problems depend on a familiarity with practical analytical and graphical techniques as well as with the theoretical methods of mathematics. We consider these practical techniques at this point references to them were made in earlier chapters for the solution of specific problems. [Pg.531]

The system of non-linear equations has been solved by the multidimensional Newton-Raphson technique which involves the successive solution of a linear system of equations ... [Pg.5]

This form is convenient in that the active inequality constraints can now be replaced in the QP by all of the inequalities, with the result that Sa is determined directly from the QP solution. Finally, since second derivatives may often be hard to calculate and a unique solution is desired for the QP problem, the Hessian matrix, is approximated by a positive definite matrix, B, which is constructed by a quasi-Newton formula and requires only first-derivative information. Thus, the Newton-type derivation for (2) leads to a nonlinear programming algorithm based on the successive solution of the following QP subproblem ... [Pg.201]

Successful solutions to the a-halogenation of ketones have also emerged, but here the problem is that sterically very hindered catalysts that work very nicely with aldehydes are not active with ketones. Some current solutions to this problon are summarized in Scheme 31 [314,317,318]. [Pg.59]

Asymmetric hydroboration of styrenes employing diphosphine complexes provides a successful solution to the generation of chirality at a benTyhc site, a potentially important route to many bioactive molecules. Since substitution on the double bond leads to severe loss of enantioselectivity, the apphcations are necessarily hmited. It was adventitiously discovered that the P,N-ligand QUINAP [47], which is effective in asymmetric... [Pg.43]

As already emphasized, the initial physical problem and successful solution is often referred to as the inverse problem in the applied mathematics literature. In the engineering literature, the subsequent repeated application of a developed numerical approach to other examples from the same general class of problems is frequently referred to as system identification. [Pg.152]

In the present paper we demonstrated the feasibility of a semiempirical description of electronic structure and properties of the Werner TMCs on a series of examples. The main feature of the proposed approach was the careful following to the structural aspects of the theory in order to preclude the loss of its elements responsible for description of qualitative physical behavior of the objects under study, in our case of TMCs. If it is done the subsequent parameterization becomes sensible and successful solutions of two long lasting problems semi-empirical parameterization of transition metals complexes and of extending the MM description to these objects can be suggested. [Pg.500]

With convergent evolution, successful solutions arise independently in different animal lines separated in time and place. The reason for the similarity of solutions is clear Animals encounter similar environmental problems and cope with them in a similar way because that solution is an efficient one. These universal solutions will be found on other planets with life. [Pg.237]

In most of the research summarized here, a homebuilt UHV-compatible Aarhus STM instrument (Fig. lb) was used, which represents a successful solution to the problem of designing a stable high-resolution microscope (55). It features state-of-the-art atomic resolution, and the compact, rigid design with a high mechanical frequency also allows for high sampling frequencies (i.e., fast data acquisition that enables observation of dynamic processes on the surface) (57). [Pg.102]

The crucial problem associated with the use of homogeneous rhodium catalysts in industrial hydroformylation is catalyst recovery. Because of the high cost of rhodium, it is necessary to recover rhodium at the ppm level to ensure economical operation. A highly successful solution to this problem was the development and application of the aqueous biphasic catalysis concept. [Pg.387]

© 2019 chempedia.info