To achieve additional interactions

Histaprodifen, a 3,3-diphenylpropyl substituted analog of histamine, is a potent histamine Hj receptor agonists. The increase in potency between histamine and histaprodifen may be due to a new orientation of the imidazole ring caused by the space filling substitution at the 2-position. This new orientation allows an additional interaction with the Hi receptor.  

FIGURE 20.53 The antitumor activity of the carboxamide and of the sulfonamide is completely abolished for the corresponding free carboxylic acid.  

FIGURE 20.54 Lipophilic derivatives of nipecotic acid and of guvacine. 

FIGURE 20.55 Large aromatic substituents attached to 5-(4-piperidyI)-3-isoxazolol. 

Several marketed compounds are using the butterfly chains with different spacer length, with substituents on the phenyl rings (more often fluorine), and/or substituents onto the carbon bearing the two phenyls (alkyl, amide, hydroxyl, nitrile. ..). 

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Instead of ensuring high lipophilicity, aralkyl groups sometimes serve to achieve additional interactions with the target macromolecule. This is t5cpically the case for the... 

An important observation by Naumann and Matter is the identification of additional opportunities to achieve selective interactions in the kinases phosphate binding region, whereas most work so far has focussed on the purine binding regions. 

The assumed transition state of this reaction is shown in Scheme 5.3. Yb(OTf)3, (J )-(-h)-BINOL, and DBU form a complex with two hydrogen bonds, and the axial chirality of (J )-(-h)-BINOL is transferred via the hydrogen bonds to the amine parts. The additive would interact with the phenolic hydrogen of the imine, which is fixed by bidentate coordination to Yb(III). Because the top face of the imine is shielded by the amine, the dienophiles approach from the bottom face to achieve high levels of selectivity. 

The treatment of blends as a two phase system opened up an interesting field of modifying the composite properties by the use of a (third component within the interface boundaries, which is termed as compatibilizers [1]. Such modifications are still being extended to the formation of microgel out of the interaction between the two blend partners having a reactive for functionalities. This type of interchain crosslinking does not require any compatibilizer to enhance the blend properties and also allows the blends to be reprocessed by further addition of a curative to achieve still further improved properties [3,4]. Such interchain crosslinking is believed to reduce the viscoelastic mismatch between the blend partners and, thus, facilitates smooth extrusion [5,6]. 

Most studies on heat- and mass-transfer to or from bubbles in continuous media have primarily been limited to the transfer mechanism for a single moving bubble. Transfer to or from swarms of bubbles moving in an arbitrary fluid field is complex and has only been analyzed theoretically for certain simple cases. To achieve a useful analysis, the assumption is commonly made that the bubbles are of uniform size. This permits calculation of the total interfacial area of the dispersion, the contact time of the bubble, and the transfer coefficient based on the average size. However, it is well known that the bubble-size distribution is not uniform, and the assumption of uniformity may lead to error. Of particular importance is the effect of the coalescence and breakup of bubbles and the effect of these phenomena on the bubble-size distribution. In addition, the interaction between adjacent bubbles in the dispersion should be taken into account in the estimation of the transfer rates... 

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