Structure-activity relationship compounds

Structure-Activity Relationships. Compounds of the B series were generally more potent than those of the A series. Thus an unsubstituted hydroxy group at the 5-position is activity enhancing (19). Differences in potency between the 1- and 2-series varied among parasites, but in most instances the 1-series was more potent. Reduction of the 22,23-olefin had little effect on activity but further reduction caused a substantial decrease in activity. The monosaccharides were two- to fourfold less active than the parent compounds while the aglycones were more than thirtyfold less active. Table III. Acetylation at the 4 -position caused no change in activity whereas acetylation at the 5- or 23- position caused a considerable decrease in activity. Diacetates and triacetates showed similarly reduced activity. Table IV (20). 

Given the potential importance of the biological effects of 24, we decided to study its structure-activity relationships. Compounds 25 and 26 were obtained from 24 by chemical hydrolysis [36]. Both silphinene analogs were strong CPB antifeedants with activity levels similar or lower to 24 in choice and no-choice tests (table 10). 

A challenging task in material science as well as in pharmaceutical research is to custom tailor a compound s properties. George S. Hammond stated that the most fundamental and lasting objective of synthesis is not production of new compounds, but production of properties (Norris Award Lecture, 1968). The molecular structure of an organic or inorganic compound determines its properties. Nevertheless, methods for the direct prediction of a compound s properties based on its molecular structure are usually not available (Figure 8-1). Therefore, the establishment of Quantitative Structure-Property Relationships (QSPRs) and Quantitative Structure-Activity Relationships (QSARs) uses an indirect approach in order to tackle this problem. In the first step, numerical descriptors encoding information about the molecular structure are calculated for a set of compounds. Secondly, statistical and artificial neural network models are used to predict the property or activity of interest based on these descriptors or a suitable subset. 

The fundamental assumption of SAR and QSAR (Structure-Activity Relationships and Quantitative Structure-Activity Relationships) is that the activity of a compound is related to its structural and/or physicochemical properties. In a classic article Corwin Hansch formulated Eq. (15) as a linear frcc-cncrgy related model for the biological activity (e.g.. toxicity) of a group of congeneric chemicals [37, in which the inverse of C, the concentration effect of the toxicant, is related to a hy-drophobidty term, FI, an electronic term, a (the Hammett substituent constant). Stcric terms can be added to this equation (typically Taft s steric parameter, E,). 

The reliability of the in silico models will be improved and their scope for predictions will be broader as soon as more reliable experimental data are available. However, there is the paradox of predictivity versus diversity. The greater the chemical diversity in a data set, the more difficult is the establishment of a predictive structure-activity relationship. Otherwise, a model developed based on compounds representing only a small subspace of the chemical space has no predictivity for compounds beyond its boundaries. 

Poso A, R Juvonen and J Gynther 1995. Comparative Molecular Field Analysis of Compounds wii CYP2A5 Binding Affinity. Quantitative Structure-Activity Relationships 14 507-511. 

Structure—Activity Relationships. In spite of the considerable synthetic and bioassay effort involved in estabhshing the thyromimetic potency of thyroid-hormone analogues, more than 100 compounds have been studied (Table 2). The main stmctural requirements for thyromimetic activity can be summarized as follows (6,12—16). 

In 2000, Simig et al. began to conduct structure activity relationships on 25 by employing the Pictet-Gams reaction. Compound 25 had been identified as an anxiolytic agent that does not show sedative side-effects. ... 

The structure activity relationships ( SAR) of newly synthesized analogues of nucleosides, xanthine heterocycles, and nonxanthine heterocycles have been explored at the ARs. Potent and selective AR antagonists have been prepared for all four subtypes [3, 4], and selective agonists are known for three subtypes [1]. Thus, numerous pharmacological tools are available for in vitro and in vivo use (Table 2). Potent and selective A2b AR agonists are yet to be repotted, although several research groups have identified lead compounds. 

Compound optimization, to screen a series of therapeutic diug candidates to find the compounds that are most specific for the target protein and those that cause unintended effects, i.e. improved understanding of the molecular mode of action including structure-activity relationships for on-target versus off-target effects... 

Nagase H, Hamasaki T, Sato T, Kito H, Yoshioka Y, Ose Y (1991) Structure-activity relationships for organotin compounds on the red killifish Oryzias latipes. Applied Organometallic Chemistry, 5(2) 91-97. 

Traditionally, in pursuit of their structure-activity relationships, medicinal chemists had focused almost exclusively on finding compounds with greater and greater potency. However, these SARs often ended up with compounds that were unsuitable for development as pharmaceutical products. These compounds would be too insoluble in water, or were not orally bioavailable, or were eliminated too quickly or too slowly from mammalian bodies. Pharmacologists and pharmaceutical development scientists for years had tried to preach the need for medicinal chemists to also think about other factors that determined whether a compound could be a medicine. Table 1.1 lists a number of factors that determine whether a potent compound has what it takes to become a drug. Experimentally, it was difficult to quantitate these other factors. Often, the necessary manpower resources would not be allocated to a compound until it had already been selected for project team status. 

In 1868 two Scottish scientists, Crum Brown and Fraser [4] recognized that a relation exists between the physiological action of a substance and its chemical composition and constitution. That recognition was in effect the birth of the science that has come to be known as quantitative structure-activity relationship (QSAR) studies a QSAR is a mathematical equation that relates a biological or other property to structural and/or physicochemical properties of a series of (usually) related compounds. Shortly afterwards, Richardson [5] showed that the narcotic effect of primary aliphatic alcohols varied with their molecular weight, and in 1893 Richet [6] observed that the toxicities of a variety of simple polar chemicals such as alcohols, ethers, and ketones were inversely correlated with their aqueous solubilities. Probably the best known of the very early work in the field was that of Overton [7] and Meyer [8], who found that the narcotic effect of simple chemicals increased with their oil-water partition coefficient and postulated that this reflected the partitioning of a chemical between the aqueous exobiophase and a lipophilic receptor. This, as it turned out, was most prescient, for about 70% of published QSARs contain a term relating to partition coefficient [9]. 

Zhao IS, Wang B, Dai ZX, Wang XD, Kong LR, Wang LS. 3D-quantitative structure-activity relationship stndy of organophosphate compounds. Chinese Sci Bull 2004 49 240-5. 

Rose SL, Jurs PC. Computer-assisted studies of structure-activity relationships of A-nitroso compounds. J Med Chem 1981 25 769-76. 

Structure—Activity Relationships Among iV-Nitroso Compounds... 

Most relevant for the affinity for A9-THC and analogs to CB-receptors are the phenolic hydroxyl group at C-1, the kind of substitution at C-9, and the properties of the side chain at C-3. Relating to the structure-activity relationships (SAR) between cannabinoids and the CB-receptors, many different modified strucfures of fhis subsfance group were developed and fesfed. The most important variations include variations of the side chain at the olivetolic moiety of the molecules and different substitutions at positions C-11 and C-9. One of the most popular analogous compounds of A9-THC is HU-210 or (-)-trans-ll-OH-A8-THC-DMH, a cannabinoid with a F,l-dimethylheptyl side... 

---