Hydrophilic compounds, hydroxylation producing

Cyclodextrins are macrocyclic compounds comprised of D-glucose bonded through 1,4-a-linkages and produced enzymatically from starch. The greek letter which proceeds the name indicates the number of glucose units incorporated in the CD (eg, a = 6, /5 = 7, 7 = 8, etc). Cyclodextrins are toroidal shaped molecules with a relatively hydrophobic internal cavity (Fig. 6). The exterior is relatively hydrophilic because of the presence of the primary and secondary hydroxyls. The primary C-6 hydroxyls are free to rotate and can partially block the CD cavity from one end. The mouth of the opposite end of the CD cavity is encircled by the C-2 and C-3 secondary hydroxyls. The restricted conformational freedom and orientation of these secondary hydroxyls is thought to be responsible for the chiral recognition inherent in these molecules (77). 

The imidazole hydroxyl SC linker 1.30 (87) linked to hydrophilic PS resins has been employed for loading acids and C-terminal Fmoc-protected amino acids. Activation and deprotection of functional groups is performed by TFA treatment, which produces the imidazole TFA salt. The imidazole ring intramolecularly attacks the ester bond upon neutralization at pH 7 with aqueous buffer and releases the compound as the free acid into solution. 

The introduction of hydrophilic groups, such as hydroxyl, amino, or carbonyl, into the barbiturate side-chains results in complete loss of hypnotic activity. Many such derivatives have been made in recent years, with the object of producing other types of pharmacological action. Examples of such compounds are provided in the sections which follow. It was recognised at an early date that the hypnotic activity of the barbiturates was related to their lipophilicity. In 1899 Meyer and Overton [159] had proposed that all chemically indiiferent bodies which are soluble in lipids act as narcotics to living protoplasm. It was then assumed that relative activities of various narcotics depend on their distribution between body fats and fluids. 

A procedure similar to that above described, i.e. the choice of hydrocarbon compounds as reference molecules in order to evaluate contemporaneously the effects connected to the formation of a cavity and to the hydrophobic hydration, was first applied to the partial molar volumes by Terasawa et al. (61). In this case, of course, in equation 2 the intrinsic volumes V, calculated according to Bondi (101), of the molecules are to be considered instead of surface areas and AX (R) identifies itself with Comparison of hydrophilic solutes with imaginary hydrocarbons with exactly the same dimension allows to deduce that the interaction water-hydrophilic centres produces a shrinkage a(Y) in the volume, f.i. the partial molar volume of solutes containing one hydroxyl group is lower by 4.3 ml mol than that of the hypothetical hydrocarbon with the same intrinsic volume. Some other values of the shrinkage in volume due to some polar centres are (in ml mol ) ... 

Typical primary particle sizes of synthetic silicas are 0.01 to 0.10 pm and a BET surface area of 50 to 800 m /g. The refractive index of synthetic silica is 1.45, which is close to refractive indices of polymers, making it possible to produce translucent and transparent filled polymer compounds. The surface of synthetic silica contains hydroxyl groups called silanol groups, which easily tend to form hydrogen bonds with water molecules and demonstrate hydrophilic character. 

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